hello bisque 132 this is the beginning of recorded lecture two one uh getting into chapter 24 fungi so you know at the top let's talk about some of the basic characteristics of fungi's fungi traits they have a cell wall made of a polysaccharide called chitin so we've talked cell walls before bacteria had a cell wall made of peptidoglycan protists had all sorts of cell walls but for fungi it's very distinctively this thing called chitin fungi can be single celled or multicellular single celled or unicellular fungi are collectively called quote-unquote yeasts so this is a single group of single-celled fungi uh yeast is not an evolutionarily relevant term this is not going to be a clade this is not going to be a a specific group this is just sort of a catch-all term when you're talking about a fungus that's single-celled you could call it a yeast so there are single-celled fungi out there called yeasts what is perhaps more interesting are the multi-cellular fungi so multicellular fungi produce these unique structures called hyphy so this is defined in the key terms but let me show you what these can look like these are these long filamentous structures the key terms define hyphy as a fungal filament composed of one or more cells so this is showing multiple cells this is showing one cell this is also getting into my next point that there are two types of hyphae hyphae where the individual cells are separated from one another by these walls called septa this is called septate hyphae uh and seen acidic hyphae uh to do not have a septa where the you know the it's one multi-nucleated cell the cytoplasm just sort of flows along the length of this let me show you this concept in just another figure from a different source just to show the same thing in a different way i like this one because this also shows that the septum in these septate hyphae has a pore in the middle so even though these cells are separated from one another by a wall a septum it's not a perfect separation cytoplasm can still and nutrients can still to an extent flow from cell to cell to cell very very quickly this is a reason why fungi if you see ever seen like a mushroom pop up in the lawn overnight you wake up the next morning and there's some mushrooms out there that weren't there before this is part of why they're able to grow so quickly uh because of the movement of nutrients through these hyphae and here's the stain acidic hyphae so in summary two types of uh fungal hyphae septic hyphen that have cell walls called septa that again incompletely separate the cells because of the pores and xenocitic hyphae that are one big multi-nucleated cell now uh one hypha is not gonna be enough for the purposes of a fungus so fungi multicellular fungi are gonna take a bunch of hyphae and put them together in what's called mycelium the key terms define mycelium simply as a mass of fungal hyphae the purpose of this is to increase surface area for uptake of nutrients fungi are the the champions of absorbing stuff in the environment around them and by having lots and lots and lots of these structures kind of like the roots of a plant but as we're going to see later in this chapter much better than the roots of a plant by having lots and lots and lots of these all spread out it makes them really great at absorbing stuff and this mycelium uh makes up the bulk of a lot of fungi so this you know there's a cross sections is showing the the substrate or the soil basically of where these mushrooms are growing uh and this is just an interesting thing to to look at and when we think of a fungus we think of a little mushroom like this we probably think oh yeah that's that's the that's the organism that's that's the fungus right here um well this is really only a small part of the fungus the vast majority of the fungal cells are actually below the ground as part of this mycelium and again if you were to use a microscope you would see this mass of white stuff it's just a bunch of fungal hyphae uh that are absorbing nutrients from their surroundings so the fact that we only see the mushroom and everything else is hidden gives us kind of a skewed perspective i mean uh imagine if uh you were looking at a tree and the whole tree was invisible except for the flowers uh that would be very strange so uh what we're looking at here is just a part of the mushroom that's used for reproduction the vast majority of its actual bulk is hidden from view underground in uh in the form of mycelium so fungi even though they are absorbing stuff from their surroundings usually dead organic matter um they're heterotrophs they're not doing photosynthesis and they're mostly sap robes uh so actually i defined this in the the key terms the last chapter but i believe it's in the key terms for this chapter as well because it's a new exam uh sap robes are an organism that derives nutrients from decaying organic matter we talked about these with oo my seeds the protists but yeah fungi are mostly sap robes there are some exceptions to this some are parasites and some are actually predators so here's a ringworm despite the name ring worm this is not a worm causing this it's a fungus so that's a parasite saprobes you know growing on this dead log here and yes there are even some fungi that are predators here's one forming a loop around this nematode roundworm we'll talk about them when we talk about animals uh and yeah it's it's attacking this worm it's gonna uh digest it and get nutrients from it so uh but all three of these strategies they all fall under the umbrella of of heterotrophy they're not doing photosynthesis they're getting their uh their energy and their carbon from organic compounds one way or another now to also talk about uh you know where they how they get their energy fungi can be obligate a robes obligate anaerobes or facultative anaerobes oh that's that's quite a mouthful of terminology and as you can see all three of these are in the key terms but if we break down these terms i it'll make it'll be easier to understand and remember a robe means you need oxygen if you think about like doing jumping jacks or something like that that's aerobic exercise aerobic means you need oxygen and a robe is the exact opposite and or a always means without or lacking so if a road needs oxygen and a robe means without oxygen now obligate means you have to you have an obligation to live this way and facultative means you could go either way so with those defined each of these three terms should make sense obligate a robe means you need oxygen to live this should sound familiar this is our lifestyle humans are obligate a robes and most your common mushroom fungus they're obligate aerobes as well obligate anaerobes means you have to live in an environment with no oxygen there are plenty of parasites parasitic fungi that live in environments where there's no oxygen those would be called obligate an aerobes and the third one's kind of weird facultative anaerobes again facultative means you can go either way this would be a fungus that could live in the presence of oxygen but it could also survive in the absence of oxygen go either way facultative brewers yeast is an example of this it can survive with oxygen if it runs out of oxygen it can start fermenting ethanol and it can survive in a no oxygen environment as well so they're all formally defined in the key terms but you know understanding the the two words that make these up uh will will help you remember these and here's a cool diagram here showing differing levels of oxygen concentration in a tube so oxygen is going to be high at the top of the tube and low at the bottom of the tube obligate a robes are only going to be able to live here where the oxygen levels are high obligate anaerobes are only going to be able to survive down here where they're away from this oxygen and facultative anaerobes they could live anywhere uh within this tube so just a visual showing those three types fungi can be any of these three now uh many fungi can reproduce asexually uh we'll see the complicated sexual life cycle as we as we get into different groups but a lot of them can reproduce asexually through a couple of different means uh one of these is through fragmentation which is exactly what it sounds like a new organism grows from a fragment of hyphae so to take this exact diagram i had before a fungal hyphae something happens to it it gets broken by some mechanical force or you know whatever this fragment of hyphae after the damage then grows into a new organism that's fragmentation that's asia asexual reproduction that's not the only way to do this we also see budding specifically in these yeasts these unicellular fungi we can see this under the microscope so yeah here's uh it's hard to get both in focus at the same time uh but yeah here's a fungal cell in the process of budding it's basically just cloning itself asexual reproduction and there's another way uh called uh spores um gonna be kind of confusing because we're gonna see a lot of different spores but spores are in many groups of fungi a form of asexual reproduction where these spores are released from a structure called the appropriately named sporangium so here we go at the tip of a hypha there's the sporangium it's going to release these spores and they can grow into a clone of this fungus just a third means of asexual reproduction now that if you thought that was complicated uh a lot of fungi can also reproduce sexually and uh here's the diagram for this uh it looks more complicated than it actually is the reason i want to get into some of the detail here when we get to specific groups of fungi one of the defining traits of many of these groups is going to be how they they differ in this basic life cycle so this is sort of a very plain generic fungi life cycle we will see variations of this in in various more specific groups so to to start out it's a circle but i mean you got to start somewhere uh let's start uh right here with two different mating strains they're not called male and female two different mating strains coming together and fusing their cytoplasms so at this point you have a cell with two nuclei because they haven't fused their nuclei yet they've just fused their cytoplasms this process is called plasmogomy so number of these steps one two three uh two mating types of haploid hyphae fused cytoplasms that's called plasmongamy we now have a dikariotic cell and just to remind you i know i use these terms in disk 130 haploid means one copy of each chromosome diploid means two copies of each chromosome so a lot of fungi just you know their regular mycelium is haploid 1n each of these nuclei here the generic cell just has one copy of each chromosome this is different from our cells in a in an animal a human so you know one uh plus one equals well it's not two yet because it's not diploid this is a dikariotic cell with two haploid nuclei but that's going to be followed by what's called karyogamy karyogamy is one plus one equals two it's where these two haploid nuclei fuse together to form a single diploid nucleus so step two nuclei fuse to form a single diploid nucleus that's karyogamy we now call this cell the zygote and the zygote undergoes meiosis or if you'll remember this is how our diploid cells make haploid eggs or sperm but in this case the diploid zygote is doing meiosis to make haploid spores releasing them and they're going to grow into haploid mycelium and start the whole thing over again this is where this can kind of be confusing because these are spores they're created by this sexual life cycle but they're still just called spores and over here there's the asexual reproduction that we already talked about uh they're also called spores and so i'm sorry if that's confusing but i mean it's it's the way it is whether they're generated asexually or sexually these haploid single-celled structures that can grow into a new mycelium they're called spores either way so the zygote forms haploid spores by the process of meiosis and once released these spores can grow into another haploid mycelium so again i think this is a very good figure uh to sort of um summarize what we've seen here in this again generic because we'll see variations of this uh sexual life cycle of a fungus all right with that out of the way uh let's talk about classification let's talk about groups let's talk about phylogeny well uh fungal phylogeny can be can be really complicated uh from wikipedia recognize the formatting here but yeah there are a lot of groups here and subgroups and clades and stuff like that let me simplify this a little bit here is a simplified phylogeny just showing some of the major groups uh and actually here's animals over here so uh we are relatively closely related to fungi just to show our position here so the simplified version of this shows five major groups of fungi let's go through these we'll start with this one here a group called chatridiomycota so chatridiomycota are mostly single-celled fungi but there are some notable multicellular members that have seen acidic hyphae remember that means you know one big cell no septa or divisions between between these areas one uh one single long multi-nucleated cell um these uh have a couple of claims to fame the chatridian mycota these are the only fungi that have flagella on their spores so these are using to kind of swim around a bit again flagellar things are going to see we saw a lot in protists but yeah these are the only fungi that have this structure uh another claim to well not fame but claim to infamy uh has to do uh with uh with amphibians so tritium i coda most members are aquatic as you can imagine from their their flagella on their spores and some of them are very notable parasites including remind you once again spelling is not a thing i'm on multiple choice tests but battered cotridium dendrobatiditis pretty sure i said that correctly uh but this species of a fungus causes chitridiomycosis and this is a fungal infection that's devastating amphibian populations across the globe it's uh it's it's it's pretty grim uh we'll talk about amphibians obviously when we talk about animals we talk about vertebrates and you know a part of their their life um part of their physiology their their thin skin and breathing through their skin makes them susceptible to these types of infections and uh yeah this is the main thing to know about chitradio my coda uh they're responsible for this so that's it for this group again you know some of these groups are simpler than others let's continue to move along let's go to zygomycota next so zygomycota have again seen acidic hyphae uh they form zygospores after sexual reproduction so okay to understand this we have to go back to something like this okay so i i told you uh that this was our generic fungi life cycle and that you know certain groups of fungi would be defined by how they are different from this so here's the the zygomycota life cycle there's the asexual reproduction up here you know spores and germination and more spores that's that's simple enough put that out of your mind but now we go down here where things start to get a bit more complicated so you got the mating types uh you've got your your plasmogamy but here's where things become interesting if you want to put it like that these zygospores uh that are formed here so these are not spores you know spores are haploid structures that can grow into mycelium these zygospores that are produced after karyogamy those can resist harsh conditions before going on to to meiosis and then producing the more traditional haploid spores so okay if this is very confusing to you here's my here's my summary of this uh these zygomycota form zygospores after sexual reproduction these are diploid spores and again that's different from the haploid spores that we're used to they resist harsh conditions they can germinate and form stocks and then go on to disperse these traditional haploid spores from a traditional sporangium but uh no no other group makes these sort of zygospores hence the the zygomycota just trying to get bogged down in all the detail here but but sometimes a visual is good uh a notable member of zygomycota is rhizopus stalinifer this is more commonly known as black bread mold and yep if you leave bread out for too long you'll see it turning you know sort of black and white like this fuzzy on the outside if you looked very very closely at this you would see these white filaments those are the stalks and little tips of those filaments like the little head of a pin these little black things uh those are the sporangia which are releasing spores part of their life cycle so that's what's going on with this uh with this bread mold okay that was zygomakota let's move over skipping these for now uh to asco my coda so another one of these uh so okay what's what's special about this so again you got the asexual reproduction that's that's easy to take care of you've got mating strains you've got plasmogamy you've got mitosis so okay this is kind of different plasmogamy is when you have haploid plus haploid and you get this this dikariotic cell this cell with with two uh different nuclei uh normally plasmogamy would go straight to karyogamy and you would fuse one plus one to two but in ascomycota you have plasmogamy and then mitosis so you end up creating this small multicellular structure with several dikaryotic cells you'll notice each of these cells has two different nuclei from the two different mating strains that created these are kind of color coded for your convenience here so this uh the tip of this cup like structure the cup like structure is called an ascocarp the cells at the the tip of this cup uh is is are called ascai or ascos is a single one of these cells it is only in the ascus cell that you finally get one plus one equals two karyogamy followed by meiosis followed by mitosis to create a very distinctive number exactly eight haploid spores or ascospores because they're from an ascos those can be released and germinate and form another haploid mycelium so okay how do i how do i summarize this uh if you want to put this into words after plasmogamy a dikariotic that means two nuclei sac like asco carb forms the cell at the tip of the cup is called an ascus the ascus does karyogamy meiosis then mitosis making exactly eight haploid ascospores uh and then they're released and and for more uh more mycelium so again a lot of this is similar with the generic life cycle but this is is different in uh in a unique way uh there are a lot of notable members of ascomycota um canada albicans a pathogen responsible for oral thrush yeast infections morels and truffles which are edible mycorrhizae and lichen which we'll talk about later in this chapter many plant diseases and the two that i actually want to call out penicillium uh creo cresogenium which penicillium might sound familiar to you this is our source for penicillin we did not invent penicillin this antibiotic we stole it from nature fungi have been waging war with bacteria for longer than we've been around uh and it was just the discovery of this compound created by a fungi uh that we were able to use and then eventually modify and uh it was really very uh impactful in human history so this is a notable number of ascomycota uh the other notable number i want to actually call out is saccharomyces cerevisiae uh also known as baker's yeast or brewers yeast and yeah you'll see the stuff in the the grocery store this is the fungus that is used to uh make beer uh or to or to make bread so not as you know uh crazy as penicillin but you know something very very commonplace and this uh this fungus is a member of ascomycota okay moving along uh now we're moving into basidiomycota and you guessed it another one of these uh so okay this one uh isn't even showing the asexual uh life cycle of this uh what's go what's going on here so okay you have haploid primary mycelium haploid primary mycelium plasmogomy that's you know the fusing of cytoplasms you got dikaryotic cells here and like the ascomycota you have mitosis here after plasmogony so you know the two matings uh types fuse together you've got a dikariotic cell but then mitosis leads to a multicellular dikariotic structure now this is different from ascomycota because in ascomycota the the dikariotic cells just formed a little cup a microscopic little cup but basidiomycota takes this several steps further this dicaryotic structure actually forms its own mycelium so if you look at a mushroom for example you or all of the cells in that mushroom are dicaryonic it has its own mycelium underground that is dicariotic the majority of this life cycle is in a form that is dikaryotic two haploid nuclei so this this dicarionic stage you know goes on for for way longer than in in any other group of fungi so yeah all of this stuff is dikaryotic uh the so here's what i have to say about this oh i'm sorry here's what i have to say about this to sort of start uh haploid primary mycelium undergoes plasmongamy to form dikariotic secondary mycelium and these are the terms here the primary mycelium is haploid the secondary mycelium is dikariotic and yeah the secondary mycelium is the the dominant structure it grows and forms the mushroom which is called the basidiocarp that's where they get their name the sidiomycota their mushrooms are basidiocarps it is only in the mushroom specifically in the gills called the basilia that you finally have one plus one equals two you get those dicariotic cells forming a diploid zygote uh which undergoes meiosis and then division and then you can release these spores to grow into a new haploid mycelium so in in the club-shaped basidia in the gills of the mushroom you have karyogamy dikariotic to diploid one plus one equals two then meiosis and cell division to make a distinctive number for haploid basidiospores which you know go off to form new primary mycelium and can repeat this cycle again so essentially this is an organism with with two multicellular stages this you know sort of free living primary mycelium and this free living dicaryotic mycelium as well so uh you know mentioning mushrooms obviously there are a ton of notable members of basidiomycota this includes uh shelf fungus if you've seen these growing on a tree in the forest or something and and all toadstool type mushrooms some are edible some are not edible uh but yeah all these classic looking toadstools or mushrooms or whatever are members of this basidiomycota group now side note so some members of ascomycota and some members of basidiomycota don't do any of this stuff that we just talked about they don't have any of this sexual life cycle at all these ascomycetes and basidiomycetes that don't do sexual reproduction are called imperfect fungi kind of a hurtful way of doing this but you know whatever all they can do is reproduce asexually um they're called imperfect fungi or sometimes they're called molds so again the quotes here tell you that this is not a clade this is not a phylogenetically important group it's just you know sort of an umbrella term uh ascomyce it's in decidion my seats that don't do sexual reproduction they're imperfect fungi they're molds okay one final group here glomeromycota this is a somewhat recently identified group it was uh newly established uh difficult to to really nail down before genome sequencing and then sequence alignment so what's their deal uh globero mycota only do asexual reproduction oh so they're imperfect fungi and molds right no so let's read this again uh the ascomycetes and basidio my seats that don't do sexual reproduction they're called imperfect fungi or molds as an entire group glomerulomycota doesn't do sexual reproduction but these are not considered to be molds or imperfect fungi so i hope that makes sense um so what's their deal uh well okay because they're only asexual thankfully we don't have another life cycle to go through uh almost all glomerulomycota form what's called arbuscular mycorrhizae uh this is in the key terms but i'm actually not going to get into this now we'll talk about mycorrhizae later in this chapter soon enough uh and and then this will make sense then if you sort of go back and read this but yeah that's that's all i want to say about global mycota asexual only uh most of these their claim to fame is is uh their involvement in our muscular mycorrhizae with these uh with the groups of fungi out of the way let's turn our attention uh very briefly to the ecology of fungi so it's some more big picture stuff kind of like we did with bacteria as well so fungi in ecosystems fungi are present in virtually all ecosystems you know we think of mushrooms and stuff as being on forest floors but they're everywhere they're in aquatic ecosystems as well there are even fungi that are plankton to use that term from the previous chapter so they're they're almost everywhere and the fungi they're sap robes uh are very important decomposers bringing up this again the carbon cycle again i mentioned this with bacteria but uh you know a lot of fungi are very important in taking uh carbon uh you know from from dead things uh or from poop or whatever and and sending it back to co2 in the air very important as part of this overall carbon cycle um many fungi participate in symbiotic relationships so you know we talked about symbionic relationships in disc 130. all of these are from disc 130 but you know maybe it's been a while uh i i've put these key terms into into this chapter's key terms as well so just to review a symbiosis or a symbiotic relationship is a close interaction between individuals of different species over an extended period of time so working together in a long-term meaningful way and three types of symbiotic relationships mutualism parasitism and commensalism mutualism is uh when both species benefit both members of this symbiotic relationship benefit it's mutually beneficial parasitism is where one benefits and the other one is harmed we know what parasites are so one benefits and the other one is harmed and commensalism is a symbiotic relationship in which one member benefits and the other is neutral it's not helped then it would be mutualism it's not harm then it would be parasitism but one is positive and the other is neutral that's what that's what commensalism is so um it's actually a lot because there are a lot of symbiotic relationships uh to talk about with fungi some of them very important and very interesting i'm not going to be able to finish this in this recorded lecture so this is typically where i run out of time in an in-person lecture so we'll pick back up and talk about these symbiotic relationships next time but this is the end of recorded lecture two one