hello everyone and welcome back to you microbiology in this chapter we're going to talk about microbial growth you'll notice that we will do chapter 6 first and then we'll go to chapter 5 the reason for that is because we're actually working with this media actively in lab class right now so I like to talk about this media first and then we'll talk about the metabolism in chapter 5 your next exam will cover chapters 5 6 & 7 and that's going to happen right before we go on spring break so without further ado let's go ahead and jump into this so microbial growth when we talk about microbial growth taking place we're actually referring to increase in to the number of cells not the actual cell size as when we talk about you growing we're talking about you getting bigger you getting larger we're for bacteria we're really just talking about the D populations or the number of cells increasing and the number of colonies increasing and you all have been able to witness microbial growth that happens on your plates when we did our kind of a toe fungus and when we did our environmental our very first labs or environmental testing or swabbing of different places we were noticing that the colony is increased on the bacteria and the longer you let it sit to a point in the incubator we saw that more colonies were present now in order for growth to take place there are a couple of different requirements that have to be adhere to we have physical and chemical requirements those are required physical requirements are things like temperature pH and osmotic pressure how salty something is how much water is present or I shouldn't say salty but how many of these solute particles are present or absence chemical requirements are things that the require the bacteria will require to undergo metabolism so carbon nitrogen sulfur phosphorus the oxygen for energy and even organic growth factors so the first class of requirements that we're going to talk about are physical requirements as you're probably already very intimately aware of and understand that there is a minimum temperature at which different species of bacteria it's not all bacteria require the same temperature that has to be adhere to for the bacteria to grow optimally the bacteria will have the greatest amount of growth and they'll flourish the nose if we have the best temperature and as I said before these ranges are going to change depending on the species of bacteria that we're talking about and then your maximum growth temperature is the higher temperature at which that bacteria can stand and it can continue to grow the temperature is too high then it will cause the proteins of the bacteria to do nature were unfold and if the proteins to nature were unfold and they lose their form they also lose their function and the bacteria will not be able to undergo its normal metabolism so here is a handy dandy slide it would be great discussion for a fill in the blank question on your upcoming test here as that as I said before not all bacteria require the same temperature as a growth requirement we have what we consider to be here hyperthermophiles hyperthermophiles they like a very high temperature the optimum growth temperature for hyperthermophiles is about ninety and really talking about Celsius here so it's about 93 94 degrees Celsius as the optimal growth temperature for these guys here when you think about extremophiles think about hyperthermophiles they like really really hot temperatures almost boiling water hot temperature thermophiles will like temperatures that are about 59 to 60 degrees irma sorry 60 to 61 degrees Celsius so they like warmer temperatures and what we normally see keeping in mind this is in Celsius so if your body temperature is in Celsius 37 degrees Celsius is about normal body temperature and in falen height it's like 98 99 degrees that's something that sixty degrees Celsius is pretty darn hot metafiles which are most of the bacteria that we work with are in this category of meso filed they like things that are right at about boom look at that body temperature so most organisms that we work with are meso files in our lab class and then also most organisms that are pathogenic that cause disease in your body or meso files psycho tropes are going to like a little lower mperatures kind of refrigerator temperature at about 24 degrees Celsius and psycho files kind of fit in that same category of the hyperthermophiles or the extremophiles they like really lower much much lower temperatures so cyclo troves grow at refrigerator temperatures between 0 degrees celsius at the minimum growth range and about 30 degrees Celsius at the maximum growth rate we civis these guys can cause food spoilage because they like refrigerator temperatures so if you have your peas in the back of the refrigerator that you forgot about refrigeration doesn't kill microbes it just retards or slows their growth you got computed I will forego it on them back there the time of spoiling they kind of smell weird they're probably psycho trophic bacteria that are causing that to happen for food preservation temperatures here notice that temperatures that are in this range above 60 degrees Celsius were above 140 degrees Fahrenheit so just as a comparison we have the Fahrenheit and the Celsius you can kind of have an idea what temperatures were talking about here most of the time most bacteria don't right here so unless it's a hyperthermophiles it's not going to grow at this area anything lower than 0 degrees Celsius or lower than the 35 degrees Fahrenheit also you have very slow bacterial growth it's kind of slows it down or and anything lower than that freezing you really don't have a whole lot of growth that's happening there now however in this area here between 60 degrees Fahrenheit and about 15 degrees Celsius and about 52 degrees Fahrenheit or about a hundred and thirty degrees Fahrenheit so we consider our dangerous zone so this is when many bacteria can have rapid growth and can produce a lot of toxins and pathogens and this is where we can get our food poisoning so it's best from looking at that graph and knowing what you know about food poisonings if you've ever had it is not a delightful experience that's one of the reasons why I'm a great uncle gronkle if you will who refuses to eat leftovers and I think you've had a couple of really bad bouts of food poisoning that he's just like I'm not eating leftovers um so when you are trying to preserve your food or preserve your leftovers you want to make sure that they get down to refrigerator temperature as quickly as possible and that the larger the surface area of your dish where your pan where the refrigerator for errors can get to every part of that dish the better it is so it's much more you're less likely to have food poisoning and if you take your leftovers and you put them in a series of smaller containers that have a larger surface area element that will allow for the temperature of the food to get down to refrigerator temperature faster we don't want to spend a whole lot of time in this danger zone if you will so notice that for this blue dish that's wider greater surface area more they can get to refrigerator temperature faster notice how we're only spending what about an hour hour and a half in this danger zone whereas with this larger dish here that when we get it down to get it down to refrigerator temperatures taking a little bit longer time and in fact we're spending let's see in the danger zone one two three four five hours we're spending in the danger zone member still not quite out yet so at this point this is the optimal temperature range for bacteria to replicate and to make more of themselves so we can increase the number of bacteria that are in this dish because it's larger it's deeper and the refrigerator air can't get to all of the parts of it as quickly so we end up having more bagged a greater proliferation of bacteria in this dish I've explained this to my husband and he's finally you know agreed with me on this if you make spaghetti for dinner he's like oh what's the point of putting in a tumbler addition let's just throw the whole thing in the refrigerator because I can come back in a couple hours and if I dig in the middle of it it's still warm that's not a good thing we don't want it to still be warm after you come back after a couple of hours it's been the refrigerator unfortunately he hasn't had any bouts of food poisoning that I know of and none of us have died or had horrible bouts of food poisoning but you want to make sure that your food gets the refrigerator temperature all of it as quickly as possible pH is another of our physical growth factors remember just like the temperature not all bacteria like the same pH not all bacteria like the same temperature most bacteria like a pH of between 6.5 and 7.5 and remember your pH scale goes from 1 to 14 where 7 is considered a neutral and anything less than 7 is considered an acid and anything above 7 is considered a base so being in that bacteria like pH is of about 6.5 to 7.5 they like slightly they kind of hang around this neutral area here so they kind of hang around here most bacteria especially those that are pathogenic mold in yeast like a slightly acidic pH of about 5 or 6 so molds and these kind of hang out here and then anything that likes PHS that are really really acidic those are also be extremophiles we call those acidophiles however in your stomach you have what's called Helio bacter pylori and the stomach your stomach pH is about a1 and it really likes that so it was considered in a stable acidify even though it's not an extremophiles so they just like that really acidic pH osmotic pressure or the concentration of solutes salt or sugar solids they're different bacteria have different tolerances or different things that they like for osmotic pressure a hypertonic environment or an increase in salt or sugar causes plasmolysis which means that the cell wall will shrivel up and pull away and shrink and it has caused the bacteria to die some bacteria like things that are really salted we call them extreme or obligate halophiles which they need to have high automatic pressures and to have a very high salt or sugar content some sort of high salt content on there very little water there and then we have those are called facilitative facultative halophiles not even that big necessarily like a high osmotic pressure they can tolerate or deal with it so here we have a cell that's in an isotonic solution so and this is some an idea that we've talked about before in chapter 4 refer to the cell wall and the plasma membrane then isotonic solution means that the concentration of water and solids or water and salt are equal outside the cell and inside the cell if a cell is in a hypertonic solution and it can't tolerate that high salt concentration then water is going to move from the area of low concentration where it's about 99% water inside the cell and only 90 percent water outside of it so water is going to move out and causes a cell to plasma lies or to pull away from the cell wall and shrivel up and die so now on to our chemical requirements so the first chemical that we're going to talk about is carbon carbon is a very versatile structural organic compound in fact anything that contains carbon is considered to be organic so if you're into sci-fi pics like I am you've probably heard aliens refer to humans or other parent or earth species as being you know carbon-based life-forms you are in fact a carbon-based life form helmet carbon is an organic molecule that many living things can be used as an energy source all of these things that are considered to be organic molecules proteins lipids carbohydrates nucleic acids they all have carbon as their backbone chemoheterotroph and this is an excellent fill in the blank question chemoheterotroph means that they use this chemical of carbon in this particular case not always carbon it can be something different but it uses this chemical and it eats other stuff that's what hetero means is other feed so chemical seeds or other feeding so a chemical heterotroph means that it can use a source of chemicals that it has to eat from the outside Auto means self so if you drive an automatic car it automatically changes from one gear to the next if you drive a manual car you have to shift gears when you go from one speed to the next speed autotrophs can feed themselves they'll also use carbon but they'll use the carbon in the form of carbon dioxide so there are some bacteria as we talked about in Chapter four that can undergo photosynthesis like plants and they would be considered an autotroph if a bacteria cannot undergo photosynthesis and it has to use something like oh say carbon in the form of glucose to get energy it's considered a chemoheterotroph it had to eat something else in order to meet its chemical requirements nitrogen is another chemical requirement we find it in amino acids I'm going to start starring some of these things because I think they're very important they find it amino acids and proteins on most bacteria can be composed or break down different types of proteins one test that we have for that that we are going to do is called a sim test for sulfur indle and motility with the inbuilt test we're looking to see if bacteria can use at very specific proteins of indle some bacteria can be composed at protein some cannot and that's kind of the basis of a lot of our biochemical tests whether or not this bacteria can use this chemical that's there because they all can't and that's how we're able to differentiate in one species from another one delays some bacteria can use ammonia or nitrate and we have tests that will test for that as well so they can use a nitrogen in a slightly different form and then there are a few bacteria that can actually do what's called nitrogen fixation and use nitrogen gas and actually fix that nitrogen gas in two different types of amino acids and proteins sulfur we also find in amino acids and same when we so found nitrogen and amino acids and amino acids and proteins you find the disulfide bonds that are made by amine and biotin also contain sulfur just like with nitrogen most bacteria can decompose proteins and we have some bacteria that can use sulfates or hydrogen sulfide and just like with the sim test we look for the ability of the bacteria to utilize indle and we can also look in that same to force in some hydrogen sulfide we can look to see if it makes us hydrogen sulfide which is going to be a black precipitate that comes out it makes a tube look blacks phosphorous we find in DNA RNA and a PP DNA RNA and ATP are all considered nucleic acids we also find phosphorus in the membrane and we find in the form of phosphate or po4 - is phosphate in these membranes as a major source of phosphorus so bacteria can use phosphates and break it down and rearrange them into you put them in their server configurations for the DNA - RNA or the phospholipid bilayers the hydrophilic head the phospholipid bilayer specifically trace elements are inorganic elements that are required in just small amounts they don't need a whole lot of it you know to sustain the life of the bacteria and remember as with the physical requirements that all of these chemical requirements are required in the same amount for all bacteria they're all different but for these trace and melon elements no matter what it is we need enough of it we need a little bit of it and if we don't have a small amount of it and even we don't need a whole lot if we don't have that little bit of it then that's going to be problematic for the bacteria well we'll find in chapter 5 is that a lot of these trace elements are usually enzyme cofactors that are responsible for the cell's metabolisms oxygen is also an important requirement for growth as we saw these are what we call file accolade tubes and remember from our lab with file glycolate tubes the concentration of oxygen decreases as we go from the top to the bottom of it so the first class of microbes that we'll talk about in their requirement for oxygen or obligate aerobes you find them growing at the top of the tube means that they have all the enzymes that are necessary to deal with oxygen in its toxic form and in fact that they are able to neutralize not only neutralize that oxygen but to use it to make energy and if they don't have oxygen they'll die you and my friend are an obligate arrow facultative anaerobes are both aerobic and anaerobic group is exhibited you'll find most growths at the top of the tube because that's the most effective way to make energy it's with the use of oxygen when I say energy I'm referring to ATP but notice that you've also find growth kind of growing at the bottom of the tube or throughout it because these are microbes that can if there's no oxygen present they can deal with that as well so they have some of the enzymes like catalase and then superoxide dismutase that will allow oxygen to be neutralized and to use it but they might not have all of them at the other end of the spectrum spectrum of obligate aerobes we have obligate anaerobes so we only see anaerobic growth is going to take place here so these microbes can only grow where there is no oxygen they don't have those enzymes of superoxide dismutase catalase afford oxidase they don't have the enzymes that are required to take oxygen from it's toxic form to be neutralized as a usable form of oxygen so they can't tolerate oxygen at all for Eero tolerate and really in lab we're just going to be working with these three classes but as an understanding of the theory behind all of this we have eros tolerant anaerobes which means that they they can continue to grow in the presence of oxygen so they will have some but not all of the enzymes that will have superoxide dismutase but it can only partially neutralize the oxygen they don't have catalase and they don't have peroxidase and other enzymes that are required to further neutralize that oxygen so we do see a kind of growth that happens throughout the tube and then micro arrow files they have aerobic growth but they only stand a little bit of oxygen so they can't deal with a whole lot of oxygen just a little bit of it and so we find what kind of in the middle there so they can produce lytic amounts of toxic oxygen mistakes are exposed to normal atmospheric oxygen so that's what I can only deal with just a little oxygen there so when we talk about oxygen and it's toxic form a singlet of oxygen can be boosted to a higher energy level state and it's very reactive it's not very stable at all so superoxide free radicals will form when we have this oxygen mint olive ated to the higher energy state with superoxide dismutase does is two enzyme and I'm going to highlight this enzyme and the highly all these enzymes are important but superoxide dismutase does if it turns this oxygen this free radical oxygens into hydrogen peroxide and then we have just our normal oxygen that's not at this high energy state anymore it's not so reactive at this point here the next class of ions that we have so having superoxide dismutase is a very important enzyme that's required to deal with oxygen if you're going to use oxygen so if you're going to be a facultative anaerobe should be an obligate aerobes you need to have superoxide dismutase the next class of enzymes are catalyst and peroxidase what catalase does is catalase will take that hydrogen peroxide because hydrogen peroxide is still toxic this guy's still not you know something to fool around with so we take the titration peroxide with catalase and break it down into water and to oxygen which we can deal with at this point this is an oxygen that's much more stable it's not the reactive toxic form of oxygen and then we have peroxidase that can also take hydrogen peroxide and break it down into water not all cells have catalase not all cells have peroxidase for bacterial cells even if it is a facultative anaerobe if it's a obligate aerobes gentes are that it has both catalase and peroxidase so there are bacteria that can have all three of these enzymes or they're bacteria that can only have superoxide dismutase and catalase or superoxide dismutase in peroxidase and they can deal with oxygen or if you obligate anaerobe they don't have any of these enzymes to deal with oxygen and it's toxic form so I'm not so concerned with you remembering the formulas if you will but you should know when enzymes do what superoxide dismutase takes it superoxide free radicals and turns it into hydrogen peroxide catalase breaks down hydrogen peroxide peroxidase breaks down hydrogen peroxide so onto organic growth factors so organic compounds pain for the environment things like vitamins amino acids purines if you're remedying the a even peeve if you will of the nucleotide to see appropriate scientific term for this for the building blocks of DNA and RNA those are organic growth factors that are required for the bacteria to grow biofilms I think you guys are all very well-versed on biofilms of these bacterial communities new thing about biofilm that we hadn't quite talked about yet is that they communicate with one another what we call qualm sensing so that a bacteria will not make as much of a by-product added normally would make if it's going to be toxic to the other bacteria into the community so that's form sensing is really the chemical way that bacteria are able to talk to one another and communicate with one another and it corn something also attracts more bacteria to the series's please can be a part of our community can be a part of our little hippie commune here and biofilms are good for bacteria secondly the biofilm is for you not so good especially if it's on a medical implants like a catheter or something like that or it's not really good for you as I said before they shared nutrients and they shelter shelter each other from harmful factors so now on to our media these are some definitions here I'm not going to spend any time talking about them I'm going to allow you to read them because I feel as though that we have talked about media at great length so far in lab we'll continue to talk about media and the terms of inoculating and cultures and so forth so I'm just allow you to read that because these definitions are pretty straightforward and we've discussed this in class previously so auger is kind of the base for many of our media um it's a complex polysaccharides and most bacteria cannot digest so it's why it's a great solidifying agent you put in our slants in our test tubes and in our petri dishes to allow for colonies to grow on there it gets liquid at about boiling temperature and then it solidifies at about 40 degrees Celsius so that's why it's also great to put in the incubators at 37 degrees Celsius because it's not going to get all gooey and liquidy on us a cultural media that is chemically defined means that we know exactly what we put into that media we know the exact chemical composition we know what kinds of amino acids in how much we know exactly what kinds of proteins and how much we're not just saying beef extract which is just a protein on there we know exactly what what sugars and how much you put on there so chemically defined media is very very specific whereas complex media just mean to put a bunch of stuff in there we didn't want to get specific on what we put in there like the chemical composition of the stuff but we did talk about we had some yeast extracts and beef extract maybe some plant extract in there almond so we know we've got a bunch of stuff in there so it's complex it's got more than one thing in it however the chemical composition of each of the entities that we put in we weren't concerned with that so when we talk about our nutrient broth which is the liquid media that we've been using in the nutrient agar those are great examples of complex media so when we look at this table here notice that we have the exact chemical concentration or the exact chemical consistency of each one of the items that are going into the medium for glucose it's kind of standard that we know that c6h12o6 oh that's why they did put it out in its molecular form and the same thing with water we know it's h2o so why write down this molecular form but this is a great example of what a chemically defined me would look like whereas for this this is another chemically defined media because we're saying exactly what's solved exactly what amino acid exactly what perience permitting and how much of these things we have in each of them so this is a very chemically defined media whereas for this guy here we got some peptone parse adjusted proteins and bc extracts sodium chloride auger and water so notice that we don't have any of the exact chemical cost constituents of what makes up the beef extract so what proteins are there when amino acids what sugars are present if any what lipids are present we didn't really talk about all of the things that make up beef extract we just did a beef extract for the same thing with a partially digested protein let me say what protein it is so there are several different combinations of amino acids that we could have with that so with a complex media there are many different things in there but we don't know the exact chemical composition of each one of the entities that goes into the media um in aerobic culture methods are to grow bacteria that don't want to deal with oxygen or that grow best in an area free of oxygen we can use reducing media like we've seen with file accolade tubes where as you go from the top to the bottom of the tube the concentration of oxygen decreases and we can even use a process and to make this reducing media we kind of drive off the oxygen you'll you'll not have to do it until you get to grad school if you decide to pursue a degree in microbiology or until you get into kind of your upper level microbiology classes for us it's already done we also can cultivate anaerobic bacteria in a jar with a gas pack here which is something that we've done very recently in lab and to get even fancier we can have anaerobic gas chambers which you will not find on the HAMP as a sentence community college but you may see these at some of your four-year schools or at some of the hospitals that you work at or the CDC the World Health Organization places like that that have like higher bio 50 labs they have the an actual anaerobic chamber where as you know we just kind of use a jar or we use fire black elite tubes cap no files are bacteria that like really high carbon dioxide concentrations and we can use a co2 pack or the kind of the old-fashioned way as a candle jar that will drive off the oxygen and leave the co2 present biological safety labs we are obviously a BSL one their real meaning those safety precautions that we take place BL 50 left to lab coats gloves eye protection we do use it I protection but that does not make our lab biosafety lab 2 we are still biosafety lab 1 biosafety lab - you'd probably find at more of your four-year universities where they have very different kinds of microbiology class is not just an introductory class that we have these are kind of for upper levels that are like biology or medical mycology or things like you know different aspects of microbiology biosafety lab 3 they have biosafety cabinets that prevent airborne transmission they're working with more pathogenic organisms you would work with organisms under a fume hood biosafety lab 3 are going to be in places like hospitals so Slough wash you barns any of those places have a medical school it probably has a biosafety lab 3 but most hospitals are probably biosafety level 3 for their microbiology labs and then biosafety level 4 is the highest and they not only have their own circulation in the lab that the lab is its own self-contained unit it's completely sealed negative pressure the air exhaust is filtered not once but twice but sometimes even more than that Center for Disease Control in Atlanta the World Health Organization those are biosafety level 4 these are going to be labs that are experimenting to find vaccines for things like the Zika virus or for Ebola or any of these nasty bugs these superbugs that we don't want to escape from anywhere at all so this is the highest biosafety lab level and these are labs that you kind of you don't just foam in and foam out which means you don't just say it on put the hand sanitizer in your hand and come in and wash your hands and handsome traction you leave out you have a complete hazmat suit you're showering to go into the lab you're showering to come out of the lab you don't take things home from the lab at all not even a loop you don't take anything at all out of that area and then you have these different chambers that you go through a checkpoint that you go through and and it's kind of a hazmat labs kind of deal that you get your experience there and is a beautiful picture of technicians that are working in a biosafety laboratory number four notice they're working with it we're going to under the fume hood and they even have their own oxygen supply because they are in their hazmat suits here so different types of media selected the differential once again I don't spend a whole lot of time on this because we have talked about it in lab differential media it makes it easy to distinguish colonies of different microbes blood agar examples of differentials media we see that some blood cell or some bacteria can Himalayas or break down the red blood cells and others cannot break them down so we have different levels of hemolytic activity either alpha beta betas complete team alliances alpha incomplete hemolysis and gamma means no hemolysis at all or does a differential media that we've worked with our MSA plates where we saw that either it could break down mannitol and turn the auger yellow or it could not but it can still grow there selective media will suppress some microbes and encourage others MSA is also a selective media where the Staphylococcus epidermis is shown a differential aspect of it that it didn't break down that mannitol so it didn't turn it yellow whereas staph aureus turns it yellow on the selective media the fact that there are some bacteria that just can't grow on an MSA plate a lot of gram negatives can't grow on the MS plate is too salty for them so it suppresses those and encourages the growth of others obtaining a pure culture you can ace up two techniques a colony is just a population cells that come from a single cell of attached cells and we consider that a colony forming unit we use the Streak price method to isolate cultures and to just get individual colonies to grow and we've talked about that in previous labs and this is this one option of street plate method what we do for our street plate method is that we separate into quadrants just because we're kind of newbies on here but we streak flame streak flame streak flame streak flames so that eventually what we end up with is called individual colonies in your third and fourth region in much the same way that they have individual colonies that are right here that you can pick out notice that we had more than one type of bacteria there we know that because we have these braided colonies and then we have kind of these golden color colonies here so you could pick up one of these red colonies put it on its own auger plate and still assured that that's all that's going to grow on that plate that's all that's going to be there it's that particular species of bacteria and the same thing for these gold color colonies you'd probably want to take a gold color colony that is not attached to anything like I think maybe a right back here it's kind of hard to see but it's not touching directly touching another cell so you probably want to take one of those to put on its own plate to make a pure culture ways that we preserve bacteria we can deep freeze them or we can freeze dry them we won't be doing any of that in lab but that's a technique that's used to ship bacteria and how we get them in the mail by freeze freeze drying them or deep freezing them so they're not they're not growing and dividing while they're in shipment on the way that prokaryotes are going to reproduce binary fission budding the committee oh fours or fragmentation of filaments mainly for mold and youth that sort of thing most bacteria we're going to work with will divide via binary fission which means that when bacteria is going to become too and there's just a pretty picture of that so in theory these two bacteria should be exactly the same but what we'll learn a chapter eight is that there are various different methods that we can allow for genetic diversity to take place but in a nutshell bacterial fission is just one cell becomes two cells now because we understand that we can kind of extrapolate that data and that idea that understanding to figure about how many figure out about how many bacteria are in a generation so if we have one cell and the numbers are expressed as a power of two and that still has it divided then we just have one cells and look at the visual representation of that one cell that's not to the power of any divisions gives you one cell if you have two cells better ^ you know 1 1 2 to the power of 1/2 to 2 cells for cells the number of cells you have there 1 2 3 4 because we started off with two cells are in one cell that divides and becomes 2 you end up with 4 another way to think about this is that if you're in the zero generation we only have one cell so once they'll hasn't divided it so there are no other cells there but if we have one cell and it divides and becomes two then we have that first generation that's happened so we go back to this slide we can look at that and see that you know one cell became to notice how all these cells States - because one cell becomes two then in that very first one here that we have this one cell divided in that very first generation it gave us one two cells so let me know if you're following here and we'll do some activities in class with this as well so if we're in our fifth generation the to stay the same two to the fifth power is 32 cells so what you're really thinking the mouse is said is that one cell becomes 2 2 becomes 4 4 becomes 16 16 becomes 32 32 becomes 64 and so forth and so forth and so forth so if you have this one cell after it's gone through five generations so we can use the term generation doubling or I think other terms you can use for this so generation number and cell double or divisions then that with this superscript number stands for so 2 to the fifth power is 32 one cell after Ted 10 rounds of division gives you 1,024 cells and so forth so we can just go all the way down the line now we typically work with the log number of cells because it's much easier to graph and it's a prettier graph a log number than it is to do 1 million 48:22 60 76 cells this is going to be a nightmare to graph whether graphing this it's going to be much cleaner and much more streamlined so we're just taking the log of this number and turning it into this to make it if I taking the log over the log base 10 just makes it a nicer graphical representation now because we understand that one cell becomes 2 and we understand that we can use the log of those numbers of cells to represent the same data then we can figure out about how long it takes for a generation to come about and we can figure out if we have the right information how many generations that we start off with so if we wanted to figure out if we have a hundred cells that have grown for five hours and they produce 1.7 million cells then how many generations that we get in that time and how long does it take for one generation to take place how long does it take for oneself to come - so what we do here is that we take the number of cells at the end 1.7 million and we take the log of that so as I said before we don't want to have to actually work with like 1.7 million that's just like a huge number and we don't want to have to deal with those kind of calculations so we can take that number of 1 million 723 than 20,000 cells and take the log of that which is 6.23 so let me pull my pencil out and in class I will show you exactly how to do this on various types of calculators because you will need to do this for your exam that's coming up here so the number of cells that we have the beginning will we start off with a hundred cells so the log of 100 I believe it's 2 and it is 2 now this number here will always stay the same and that's because that's just the log of 2 and if you don't believe me if you know how to do logs and just student type in your calculator so log a' 2 is point 3 0 1 and why does it always say the same because 1 so definer binary fission always becomes 2 so it's going to only stay that exact same way so now we're just going to do basic arithmetic here so 6 point 2 3 minus 2 divided by point 3 0 1 is going to give us 14 so we have 14 generations that have taken place because we understand that we have 14 generations that have taken place then we can figure out what the generation time is so we take 60 minutes times the number of hours that we have which in this problem it says we have 5 hours they're taking place plus the number of generations we have and it turns out to be a little bit over 21 so I think it's like I see exactly what it is yeah it's like 20 1.42 so 21 and a half minutes for generation or 21 minutes to get each generation out there and as I said before we will be doing this in lecture class as part of our activities too to really get a feel of this because you will have to do this for your exam and then this is just a really cool picture that shows you how much prettier and nicer it is to graph the log of something as opposed to graphing the the actual cells numbers so the last thing that we'll talk about are these different phases of bacteria growth we have the lag phase and the lag phase we're just preparing for population growth log phase where we see exponential increases in the population and in the stationary phase this is where the number of bacteria that are entering the population roughly equal the number of bacteria that are leaving it there are quite a few things that can cause equilibrium to take place if you're growing back to an enclosed space on the media that has a finite and that amount of resources and space it said you're going to have to there's going to be this change there's going to be a stationary point where we're just adolescent nutrients there and then as the nutrients in the space really start to decrease and we have that death phase which is just a logarithmic rate of deaths that takes place there for cereal delicious is something that we talked about is well in class I'm going to go through it rather quickly because we've done serial dilutions and we've talked about them but if we want to kind of calculate or approximate the number of bacteria in a sample then what we look at is that we know that we've taken one mill there's nine mils of this broth in this tube and then we took one mill and add it to it from our original inoculum or our pure culture and if we just kind of dilute it down we just kind of add zeroes because we're we're diluting it by tenfold if you will so that once we get down to this dilution factor here there is a ratio one out of a hundred thousand that we see so to calculate the number of bacteria that are in this inoculum in this dilution here we count the number of colonies that we have and we multiply it by that dilution factor so the example that we have the very bottom if we have fifty four colonies on a plate of a one to one thousand dilution and then fifty four times a thousand would tell us about the number of bacteria that are in that particular sample so as I said before this is something that we've done before and lab and we've talked about but this is a concept that you need to understand thoroughly and we'll talk about it again in class because it'll be on your exams plate counts we can count colony forming units usually we have a plate counter no more than 250 and we can count bacteria by filtrations these other methods that we can kind of measure the growth of bacteria by Counting the number of cells or colonies there um this is direct microscopic count of bacteria cells directly counting the cells just to give us an idea of how much growth we have in quantitatively speaking using actual numbers we can also use qualitative methods which means that we don't have actual numbers of bacteria or colonies that we're counting instead we're looking at the amount of growth that we see there and we can look at your biddat II just kind of eyeballing it and say well it's cloudy there bacteria growing in there well it's not cloudy there no bacteria growing in there or we can use more scientific forms where we can use a spectrophotometer which will look at how much light is transmitted through a test tube to account for the amount of turbidity so if we have 100% transmission or 0% absorbance of the bacteria in the test tube because there aren't any there then that tells us that there's nothing growing or we can have something that says we have 20% transmission and point 74 absorbance that means that there are some light rays that have been absorbed from this light by the bacteria and that all of them are reaching the light sensitive detective so this is just a measure of measuring turbidity bed we just eyeball we don't have this machine I don't think we have one but you probably will get a good chance to work with something like this in organic chemistry lab or definitely in other microbiology labs so that is all for chapter 6 the next time that we have another session it will cover chapter 5 and we'll talk about microbial metabolism