An Introduction to Fungi.pdf

This is a part of the online class for the undergraduate Botany students..

1. INTRODUCTION TO MYCOLOGY
BY
Dr P B MALLIKHARJUNA
GFGC YB
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2. Mycology –A General Account
Introduction:MycologyisabranchofBotanythatdeals
withthestudyoffungi.
Fungiarethemicroscopic/macroscopic, achlorophyllous,
uni/multicellular,eukaryotic,heterotrophic,thalloid,non-
floweringplants/livingorganisms.
Theterm‘Mykos’isderivedfromtheGreek,whichmeans
‘mushroom’and“logos”meansdiscourse.
Alaxopoulos(1952)definedfungias“thenucleatedspore
bearing,achlorophyllous,eukaryotic,heteromorphicandnon-
floweringplants/organisms”
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3. Fungiareoneofthelargestgroupoflivingorganisms
possessingabout5100generaand120,000species
today
However,theestimatedfungiisapproximately1.5
million(15lakh)fungalspeciesandeveryyearthe
mycologistsdiscoveringabout1700newfungal
species.
Thesearegenerallyreferredasthemolds,yeasts,
toadstools,mushrooms,polypores,puffballs,rusts
andsmuts.
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4. SomeoftheknownfungalgeneraareAspergillus,
Mucor, Rhizopus, Aspergillus, Penicillium,
Saccharomyces, Albugo, Peziza, Puccinia,
Cercospora,Alternaria,Helminthosporium,Rhizoctonia,
Pyricularia,Colletotrichum,Agaricus,Chaetomium,
Phoma,Ustilago,Curvularia,Fusarium,Microsporum,
Candida,Neurospora,Claviceps,Sphacelotheca,Erwinia
,Phytophthora,Pythium,andsoon.
MicheliistheFatherofMycology&AntonvondeBary
(1850)istheFounderofModernMycologyandthe
FatherofPlantPathology.
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5. IMPORTANT CHARACTERS OFFUNGI:
Fungiarecosmopolitanindistribution,occursinmostly
terrestrial;someareaquaticandsomeareairborne.
Somefungiinfectsplants,animalsandalsohumanbeings.
Theplantbodyisathallusconsistingofbranchedand
filamentoushyphaeknownasmycelium.
Cellwallcontainschitin(N-Acetylglucosamine)
Fungiaredevoidofchlorophyll,sotheyareheterotrophicin
nutrition
Reservefoodmaterialsaremainlyglycogenoroil.
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6. Theymaybeparasites:obtainingnutritionfromother
livingplantsoranimals.Ex:Albugo,Puccinia
Somefungiaresaprophytes :obtainingnutritionfrom
deadanddecayingorganicmatter,Ex:Mucor
Theyreproducesbyvegetative,asexualandsexualmethods
Vegetativereproductiontakesplacebyfragmentationby
fission/budding.
Asexualreproductiontakesplacebyspores
Sexualreproductionoccursinallgroupsoffungiexceptin
Deuteromycetes.
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7. THALLUSSTRUCTURE :
Infungiplantbodyisthallus.Thereisnochlorophyllinthethallus,sothey
needaheterotrophicmodeofnutrition
Thenatureofthallusinfungimaybeofthreetypesviz,
1.Unicellularthallus
2.Multicellularthallusand
3.Mycelialthallus
Unicellularthallusconsistsofsinglecell,thisissimpleandprimitivetype
ofthalliasinYeast,slimemoldsandmembersofchytritids.
Mycelialthallusconsistsofmicroscopicfilaments.Eachfilamentisa
linearrowofcellsjoinedendtoend.
Thehighlybranchedfilamentousthallusisknownasmycelium.Individual
branchofmyceliumiscalledahypha.
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8. Hyphaemayormaynot
havecrosswalls,the
crosswallsarecalled
septa.
Thehyphaewithsepta
iscalledseptate.Each
septumispiercedbya
porecalledseptalpore
orcentralpore.
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10. MYCELIUM :Thefungalbodyusuallyconsistsofmassof
hyphaecalledmycelium.Itmaybeintercellularorintracellular
inthehost.
COENOCYTICMYCELIUM:Inthis,themyceliumisusually
tubular,siphon-likewithoutcrosssepta.Further,itismulti-
nucleate,highlybranchedandusuallyfoundintheprimitive
fungi.Ex.Albugo.
SEPTATEMYCELIUM:itisamajortypethatoccursinadvanced
fungi.Herethefungusisfilamentous,multicellular,andhighly
branched.Themyceliummaybemonokaryoticordikaryotic.
Thecrossseptamaybesimpleordoliporeinnature.
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11. Fungalmyceliahavethefollowingmodifications,
1.Plectonema 2.Sclerotia3.Sporophores/condiophores,4.Stroma&
5.Rhizomorph
1.Plectenchyma :isacompactlyinterwovenmassofhyphae,
hereindividualhyphaearepartlyfusedandpartlyunfusedbut
closetoeachother.
2.Pseudoparenchyma :Some timesindividualhyphaeare
compactlyfusedtoeachotherandappearsasparenchymatous
tissuethiscompactportion.
3.Prosenchyma :Lesscompactstructuresconsistingofhyphae
madeofelongatedcellscalledprosenchyma.
4.Bothpseudoparenchyma andprosenchymamostlyformedduring
formationoffruitingbodiesofAscomycetesandBasidiomycetes.
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13. 2.Sclerotia:Itconsistsofa
compact mass ofinterwoven
hyphae forming pseudo
parenchyma.Theouterhyphae
become hardand forma
protectivecoveringorrind.These
bodiesremaindormantunder
unfavorable conditions and
germinate attheonsetof
favorableconditions.
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14. 3.Sporophores:Apartof
myceliumthatbearsspores
onitcalledsporophore.The
sporophore may be
branchedorunbranchedand
itmay eitherproduce
sporoangiospore or
conidiospores.
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15. 4.Stroma:isacushionlikestructureformedby
pseudoparenchymatous fungaltissue.Thesporophore
usuallyarisesfromtheStroma.Itisformedatthelater
stagesofdevelopmentofmycelium.
5.Rhizomorph:isaropelikecoiledstructureformedby
interveningoffungalhyphae.Itlookslikeasmallropeand
darkbrownincolour.Theseareformedduringfavourable
conditions.Therhizomorphproducesnewmycelium.
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16. FUNGAL CELL STRUCTURE
•Eukaryotic–1/manynucleated,Monoploid(Haploid)
(Singlesetofchromosomes)
•Cellwall–ChitinandFungalcellulose.
•Plasmamembranewithergosterols
•PresenceofSmallnucleus,Mitochondria,ER,Golgi
complex,vesicles,80Sribosomesandvacuoles,
•Thechiefreservefoodisglycogenandoil.
•Lomasomes–presenceoftheplasmamembraneoutward
foldingsandvesiclescollectivelyreferredasLomasome
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17. Yeast cell-ultrastructure
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18. FUNGAL GROWTH
•Fungalcellswillundergothemitoticcelldivisioninorder
togrowbothvegetativelyandreproductively.
•Apicalgrowthispresentinmycelialfungi.
•Thegrowthisveryrapidinfungi.Forinstance,an
individualfungusmayproducemorethanakilometerof
newhyphaewithinaday.
•Thegrowthrateisdependingbothontheavailabilityof
CN-richnutrientsandalsotheexternalfactorslike
darkness,lowtemperature,slightlyacidicpHandhigh
relativehumidity.
•BothPhytochromeandCryptochromeinvolveinthefungal
growthandmorphogenesis.
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19. NUTRITION IN FUNGI
•Asthefungiareachlorophyllous,theyobtainnutrition
bytheheterotrophicmethod.Therearethree
methods,
1.Saprophyticmodeofnutrition
2.Parasiticmodeofnutrition
3.Symbioticmodeofnutrition
•Further,themodeofdigestionisbothextracellular&
intra-cellular.Theuptakeofnutrientsisbythe
absorption.
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20. 1.Saprophyticnutrition:
•Majorityoffungiobtainitsnutritionfromthedeadand
decayingorganicmattercalledSaprophytes or
Saprobes.
•Saprophytesaretwotypes:obligatesaprophytesand
facultativesaprobes.
•Fungiwhichliveondeadorganicmatterandincapableof
infectinglivingorganismsarecalledobligatesaprobes.
•Fungiwhichusuallyliveonlivinghostandoccasionally
theyliveondeadorganicmatteraswellarecalled
facultativesaprobes.
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21. •Someofthesaprophyticfungiare;
•Coprophilous fungi:growoncattle
wasteEx.Chaetomium andPilobolus
species
•Keratinophilous fungi:growon
keratinrichdecayingsubstanceslikehair
andnails.Ex.Microsporumgypseum,
andTrichophytonterrestre.
•LignicolousFungi:thatnotonlygrow
onwoodbutpermeate itsfibrous
structureandactuallycausedecay,Ex.
ArmillariaandBrownrot,softrot&
Whiterotfungi.
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22. 2.Parasiticnutrition:
•Fungiliveonotherorganismsandobtaintheirnutritionfrom
alivinghost.
•Theseareclassifiedintoobligateparasitesandfacultative
parasites
•Obligateparasitesliveonlyonlivingorganisms(Albugo)
•Whereasfacultativeparasitesliveindeadanddecaying
organicmatterand/oronlivingorganisms.(Armillaria)
•Theyusuallydrawthenutrientsfromthehostbythe
haustoria.
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23. 3.Symbioticnutrition:somefungiliveincloseassociation
withrootsorstemsofcertainhigherplantsandthat
fungi/plantgetsomemutualbenefits.Thistypeofnutritionis
calledsymbiosis.Ex:LichensandMycorrhizae.
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24. 4.Predaciousfungi:Certainfungi
livinginthesoiltrapstheeelworms
andnematodesbymakingringsof
hyphaearoundthem.Theserings
capturenematodes andproduce
haustoriaintothenematodes.By
thesehaustoriaintothenematodes
fungiabsorbsnutrientsfromthe
nematodes.Thesefungiarecalled
predaciousfungiorNematophagous
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25. REPRODUCTION IN FUNGI
Holocarpic fungi:Fungilikeinunicellularfungi
(Synchitrium,Saccharomyces)theentirevegetativecellis
transformedintoareproductiveunit.
Eucarpicfungi:Inmajorityofmycelialfungi(Pythium,
Penicillium,Helminthosporium),onlyapartofvegetative
bodyformsreproductiveunitandrestportionremainsas
vegetative.(Albugo,Peziza,Puccinia)
Fungireproducesbythreemeans,
1.Vegetative
2.Asexualand
3.Sexualmethods
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26. 1.Vegetativereproduction:takesplacebythefollowingmethods,
I.Fragmentation:commoninfilamentousfungi(Rhizopus,Alternaria,
Fusarium)wherethehyphaebreakdownintotwoormorefragments
duetosomeexternalforceandeachonedevelopintoanew
individual.
II.Budding:takesplaceinunicellularfungi(yeast).Asmalloutgrowth
i.e.,thebudemergesoutfromparentcell.Nucleusdividesintotwo
andonepassestothebud.Thebudisthenseparatedbypartition
wall,butcontinuesitsgrowth.Lateritbreaksoffandgrow
individually.
III.Fission:normallyunicellularfungireproducesbythismethod,
wherethevegetativecellelongatesanddividesintotwodaughter
cellsofequalsizebysimpleconstrictioninthemiddlewith
simultaneousnucleardivision.
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27. Asexual reproduction
•Thisisthepredominanttypeofreproductioninfungi.
•Takesplacebymeansofseveraltypesofspores,generally
producedduringthefavourableconditions.
•Themainobjectiveistoincreaseitspopulationandthereby
occupyingdifferenthabitats.
•Thesporesmaybeunicellularormulticellular.Theymaybe
exogenousorendogenousindevelopment.
•Some ofthesporesareZoospores, Condiospores,
Chlamydospores,Oidospores,Sporangiospores,etc.
•Sometimes,theymayalsodevelopintotheasexualfruiting
bodieslikeCoremia,Synnemata,SporodochiaandAcervuli.
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28. Fruiting bodies
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29. 1. Zoospores:zoospores may be uni
or biflagellate, generally pear shaped
produced in sporangium.
Ex:Synchytrium& Saprolegnia
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30. 2.Conidia:theseareexogenouslyproduced;non-motile
sporesdevelopedbytheconstrictionattheendofspecialized
hyphalbranchescalledconidiophores.Theymaybe
single(Pythium)orinchain(Penicillium).Thesearethe
dominanttypeofasexualspores.
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A WIDE RANGE OF CONIDIA

32. 3.Oidia:insomefungi,the
hyphaltipsoftendivideby
transversewallintolarge
number ofsmallsegments
whichmayremaininchainor
becomesfreefromeachother.
Theseareknownasoidia.Ex.
Lichens
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33. 4.Chlamydospores:Theseare
thickwalled,roundtoovalin
outline,brownorblackin
coloured spores,produced
eitherterminallyorintercalary
atsomeintervalsthroughout
thelengthofhyphae,during
unfavourableconditions Ex:
Fusarium
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34. 5.Sporangiospores:theseare
globose,multinucleate,non-
motileaplanosporesformedinside
sporangium.Thesporoangiospore
germinatesbyproducinggerm
tube.Later,itdevelopsintoa
profuselybranchedmycelium.
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35. 3. Sexual reproduction
Involvestheunionofmaleandfemalegametesortwo
gametangia.
Occursduringunfavourableconditions.
Involvesgametogenesisfollowedbythefertilization.
Alargenumberoffungireproducebysexualmeansbut
deuteromyceteslackssexualreproduction.
Thegeneraltypesofsexualreproductionareasfollows
I.Planogameticcopulation
II.Gametangialcontact
III.Gametangialcopulation
IV.Spermatogamy &
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36. I.Planogametic copulation:planogametesaremotile
flagellategametes.
•Itistheunionofmotilemaleandfemalegametes
•Itisoffollowingtypes,a.Isogamy b.Anisogamy
c.Oogamy
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37. II.Gametangialcontact:
•Gametangiaarethesexorgans.
•Oogoniumisthefemalesexorgan
andAntheridiumisthemalesex
organ
•Twogametangiaofoppositesex
comeincontact,thecontentof
themaleantheridiummigrates
intofemalegametangia.
•KaryogamyandPlasomgamy ->
Oospore.
•Ex.Albugo
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38. III.Gametangial copulation:The reproductive
structuresareinvolvedinthefusion.Theentirecontentof
twocontactinggametangiafusesandprocessthediploid
structurecalledZygospore.Ex.Mucor
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39. IV. Spermatogamy : Here a small
male sperm is formed and pollinated
onto the female gametangia.
•Spermatium isthemalesexorgan
and
•TheReceptiveisthefemalesex
organ
•MorecommonintheAscomycetous
andBasidiomycetousfungi.
Ex.Puccinia
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40. V.Somatogamy :insome
higherfungibelongstothe
classes Ascomycetes and
Basidiomycetes, the sex
organsarenotproduced.
•Herethesomatichyphae
directlyinvolvesinsexual
fusion.
•Thisfusionisbasedonthe
homothallicandheterothallic
condition.
•Ex.Peziza
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41. Sexual Fruiting Bodies of Fungi
ASCOMYCTES FUNGI BASIDIOMYCETES FUNGI
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42. Role of Fungi
•Decomposers (saprophytes)
•Soil clump formation
•Improves soil fertility as Bio fertilizers
•Produce Mycotoxins/ Antibiotics/Industrial products
•Cause Plant diseases (5000 Fungi)
•Cause Human and animal diseases (175 fungi)
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43. CLASSIFICATION OF FUNGI
•Several mycologists proposed different types of classification based
on the charectersof fungi
•How ever, Ainsworth classification and Alexapoulousclassification are
adopted by many.
Theclassificationoffungiisbasedprimarilyonthecharacteristicsof
thesexualsporesandfruitingbodiespresentduringthesexual
stagesoftheirlifecycles.
However,thecompleteorperfectlifecyclesofmanyfungiareyetto
known.
Ainsworth(1973)classifiedfungiprimarilybasedonthenatureof
thallusandmoreimportantlyonthetypeofsporesproduceduring
reproduction.
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44. Albugo Penicillium Puccinia
AINSWORTH CLASSIFICATION
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TheKingdomFungiisdividedintotwo
Divisionsand9Classes.
1.Division–Myxomocotaand
2.Division–Eumycota

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possessslimemoldswithamoeboidalthallus
duetolackofcellwall;holocarpicandcoenocytic.
IthasfourClassesviz.,1.Acrasiomycetes,2.Hydromyxomycetes,
3.Myxomycetesand4.Plasmodiophoromycetes.
Class1-Acraciomycetes includesthecellularslimemoldswith
freelivingassimilatoryphaseformingpseudoplasmodium.Ex.
Dictyostelium
TheClass2-Hydromyxomycetes includesthenetlikemolds.
Ex.Labyrinthula
TheClass3-Myxomycetes includethetrueslimemoldswith
saprophyticplasmodium.Ex.Physarum
Class4.Plasmodiophoromycetes includetheendo-parasitic
slimemolds.Ex.Plasmodiophora

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DivissionII:Eumycota arethetruefungiwith
chitinouscellwall,andwitheitherunicellularor
multicellularfilamentousmycelialthallus.
Basedonthesporebearingstructures,inwhichthe
sporesareproduced,theseareclassifiedinto5sub-
divisionsnamely,
Sub-divisionI:Mastigomycotina
Sub-divisionII:Zygomycotina
Sub-divisionIII:Ascomycotina
Sub-divisionIV:Basidiomycotina
Sub-divisionV:Deuteromycotina

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Sub-divisionI:Mastigomycotina :
Aseptateandcoenocyticmycelialfungi
Themotile–flagellatezoosporesareproducedinthe
asexualreproduction.
Sexualreproductionisthegametangialcontact.
Ex.Albugo,Phytophthora
Sub-divisionII:Zygomycotina :
Aseptateandcoenocyticmycelialfungi
Asexualreproductionisbytheformationofnon-motile
sporesinsidethesporangium
Sexualreproductionisthegametangialcopulationand
theresultantZygospore,isarestingspore.
Ex.Mucor,Rhizopus

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Sub-divisionIII:Ascomycotina (Sacfungi)
Asaclikestructurecalledascusproducesorbearssexualspores
calledascospores.
Sexualreproductionoccursbysinglecelledormulti-celledconidia.
Unicellularormycelialfungi
Hyphaearegenerallyseptate.
Examples:Saccharomyces,Peziza,Aspergillus,Penicillium.
Sub-divisionIV:Basidiomycotina (Clubfungi)
Sexualsporescalledbasidiosporesareproducedexternallyona
clubshapedbasidia
Asexualreproductionoccursbybudding,fragmentationorconidia
formation
Theyarecommonlycalledasmushroomgroup.
Hyphaearegenerallyseptate.
Examples:Amanita,Agaricus,Puccinia

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Sub-divisionV:Deuteromycotina (Imperfectfungi)
Thesefungiarealsoknownasfungiimperfectii.
Nosexualstageispresentornotknown
Asexualreproductionoccursbymeansofconidia.
Septatemycelialfungi
Examples:Cercospora,Colletotrichum,

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ReferencesandSuggestedFurtherReading:
1.TextBookofFungi:BRVashishstaetal.SChand
Publications,2016.
•2.AnIntroductiontoFungi:HCDube,ScientificPublishers
,2012.
3.IntroductiontoFungi:Webster&Weber,Cambridge
UniversityPress,2007