Hey everybody Dr. O here. This video we're going to talk about temperatures effect on the growth of microorganisms so you're gonna see here we're gonna talk about these four categories then i'm gonna add a fifth one as well so it's looking at this this chart we have psychrophiles which are going to be your cold temperature loving organisms mesophile some call them mezophiles these are moderate temperature loving organisms and these are gonna be the most important thermophiles are heat loving organisms and then hyperthermophiles or some people call these extreme thermophiles are going to be extreme heat loving organisms so and then we're gonna add a category right there between psychrophiles and mesophiles called psychrotrophs which is a term that food microbiologists use so OK so first of all just look at these different ranges so most most organisms have about a 30 degrees Celsius window where they can grow so if you look at any one of these lets look at mesophiles for example what is that orange or yellow whatever it is on the far left would be that it's minimal growth temperature on the far right would be its maximal growth temperature and then the peak at the top would be its optimal growth temperature so the reason we care so much about the mesophiles is there optimal growth temperatures 37 degrees Celsius reason that so important is because that's 98.6 degrees Fahrenheit so obviously organisms have evolved and adapted to prefer the temperature of their hosts and it shows you why we have to care so much about these so a couple more things before we jump into specifics here you'll notice especially with those mesophiles and and all of them really notice that the this is not an upside down V right you've got the from minimal to optimal growth temperature you see kind of a gradual change but then it starts to drop off when you reach that that maximum growth temperature and that's because it at least we believe that that's where critical enzymes that are needed for growth are going to be inactivated by the temperature so the high temperature basically will denature or destroy the protein based enzymes and that's why you see the the growth start to fall off there OK alright so let's so really let's get the ones out of the way that really don’t matter thermophiles so these heat living organisms reason we don't care about them is because they don't grow they really can't grow below 45 degrees Celsius so they're not going to cause they're not gonna cause human disease they're not going to be pathogens and they're really not gonna lead to any issues with food spoilage I mean they might but not not as far as making you sick they're not a health concern so like for example some thermophiles will survive the ah the industrial canning process so there can be thermophilic bacteria in your canned goods and they can even spoil your food but they're not going to lead to food poisoning so thermophiles enough I gave you a good example a good example here would be ah organisms that live in compost piles they love the temperature of sunlit soils so if you're a gardener like myself and you do any composting specifically what it would be called hot composting you rely on thermolytic organisms I actually buy a container its about the size of a cereal box of a starter culture that I use when I start a new compost pile to add these thermolytic bacteria Hyperthermophiles I think of them they basically live in Hot Springs or deep sea thermal vents things that are associated with volcanic activity um they can grow even as high as the highest recorded one I believe is 121 degrees centigrade or Celsius so they're going so we don't really worry about them because our primary concern is what makes us sick and what what causes food poisoning right so so the two we're gonna focus on here that'll be the mesophiles and the psychrophiles so let's the psychrophiles um they're gonna grow relatively well in in their refrigerator and even freezer temperature so the psychrophiles really I like to think about the freezer so first of all I said relatively well because nothing grows well in the freezer these just grow well in the freezer compared to other organisms so given enough time psychrophiles can lead to food um changes of your food even even at the freezer ah temperature but they're not not a very big deal the mesophiles these are gonna be almost all your human pathogens and because mesophiles will grow at body temperature and room temperature they can lead to some some foodborne illness and food spoilage as well so so for mesophiles think human pathogen so like when we used an incubator in the lab it's almost always set at 37 degrees Celsius because that's where that's where your pseudomonas and E coli and staph and strep all these organisms that we care about grow at that temperature so the mesophiles think human disease pathogens now we've got to add this extra category so again I'll I'll show you in the video where where it is between psychrophiles and mesophiles there's this is a term that food microbiologist used called psychrotrophs and I wish you wish it was on this chart but ah but it but it isn't so psychrotrophs these are much more important than psychrophiles because these are going to lead to a lot more spoilage in the refrigerator so they lead to low temperature food spoilage they they can grow in there frigerator so if you're looking at food borne illness at lower temperatures like the refrigerator and even in a cool room it would be the psychrotrophs that were primarily concerned about so it's kind of there's there's obviously some overlap here as far as which organisms cause food spoilage it would be both the psychrotrophs especially at lower temperatures but the mesophilic organisms would cut cause food spoilage at room temperature as well but it just for all purposes if you're in one of my classes mesophiles think pathogens human disease psychrotrophs think food spoilage OK ah so those are the those are the different groupings of organisms based on the temperature they live at so that is temperatures effects on growth have a wonderful day be blessed