Fungal Biotechnology
Lecture 5
Fungal Groups & Genetics
Ectomycorrhizal Fungi
Glomeromycota (AM) Fungi,
Zygomycota & Chytridiomycota
Dr. Nadav Nitzan
The 5 fungal Divisions / Phyla
Sub-Kingdom Dikarya
Imperfect Fungi;
Conidial ascomycetes
Openstax cnx; http://cnx.org/content/m47343/latest/
Mycorrhiza
Mycorrhiza
• Myco = fungus, Rhizum = root
• Mycorhiza is a a symbiotic relationship between plant
roots and fungi
• It is primarily mutualistic, but may be weakly pathogenic
• Mycorrhiza was described by the Polish botanist
Franciszek Kamienski in 1879-1882; and was further
studies by Albert Bernhard Frank, who introduced the
term Mycorrhiza in 1885
Mycorrhiza
Types of mycorrhiza
Extracellular /
Ectomycorrihza (ECM)
Intracellular /
Endomycorrhiza /
Arbascular mycorrhiza (AM) /
Vascular Arbascular Mycorrhiza (VAM)
Ascomycota & Basidiomycota
Glomeromycoata
Ectomycorrhiza (ECM)
• Asco & Basidiomycete (Agaricales) produce ectomycorrhiza w/ plants
Ectomycorrhiza
(ECM)
• ECM root tips types
• B = Pine + Amanita muscaria
• C = Pine + Boletus edulis
http://mycorrhizas.info/ecmf.html
Ectomycorrhiza (ECM)
• In ECM the fungus DOES NOT penetrate the cell wall or the
cell
• The fungus forms a net of hyphae around the celled
Harting net
www.wikipedia.org
Ectomycorrhiza (ECM)
Harting Net
http://mycorrhizas.info/
Ectomycorrhiza (ECM)
•
ECM is a mutualistic non-obligated association between fungi and plant roots
•
Fungal mycelium may constitute up to 40% of root dry weight
•
Per 1 cm of ECM association, ~ 80 cm of hyphae is present in the soil
•
~30% of photosynthesis products are transferred from the plant to the fungus
•
Generally, sucrose is delivered to the plant-fungal interface, and converted by
invertase into hexose. Glucose is actively absorbed by the fungus and directly
converted to trehalose, mannitol and glycogen within the fungus, resulting in
the maintaining of osmotic gradient
http://bugs.bio.usyd.edu.au/learning/resources/Mycology/Plant_Interactions/Mycorrhizas/Ectomycorrhiza/EMfunction.shtml
Ectomycorrhiza (ECM)
• ECM fungi actively digest substances & absorb nutrients from the
soil, transporting them to the roots, possibly as hydrophobins, which
are small proteins (~100 aa) rich w/ cystein, produced ONLY by
filamentous fungi
• The fungi also transfer mineral (N, P, K, etc.) to the root
• Fungal material is secreted in the intracellular space, as ECM fungi
do not enter the cell
• The ability of fungi to grow under various environmental conditions
(pH, salinity, toxicity) is beneficial to the plant
Ectomycorrhiza (ECM)
• Familiar ECM fungi are:
– Amanita (Basidio)
– Truffles (Asco)
• Familiar ECM trees:
– Pinus (‫)אורן‬
– Oaks (‫)אלון‬
– Willow (‫)ערבה בוכיה‬
– Eucalyptus (‫)אקליפטוס‬
Fruiting bodies of ECM fungi associated
w/ Eucalyptus in Australia (Pisolithus, Boletes)
Mycorrhiza
Types of mycorrhiza
Extracellular /
Ectomycorrihza (ECM)
Intracellular /
Endomycorrhiza /
Arbascular mycorrhiza (AM) /
Vascular Arbascular Mycorrhiza (VAM)
Ascomycota & Basidiomycota
Phylum Glomeromycoata
Phylum Glomeromycota
Phylum Glomeromycota
• ~160 known species
• Known as Arbascular Mycorhizal (AM) fungi
• Form an obligate, symbiotic-mutualistic association
with plant roots called Endomycorrhizae
• They form this association w/ roots of ~80% of
vascular plant species
Phylum Glomeromycota
• Glomeromycetes are obligate symbionts
• Form arbuscules – a tree like organ w/in plant root cells
• Some Glomeromycetes form storage organs termed vesicles within
the root cells
• Hyphae are non-septate
• Are able to grow within plant roots without causing disease
symptoms
Phylum Glomeromycota
• Glomeromycetes produce large (40-800 µm)
spores with layered walls
• The spores are coenocytes, containing several
hundreds to thousands of nuclei (Bécard and
Pfeffer, 1993).
• Spores may be formed singly, in clusters or in
morphologically distinct "fruitbodies" called
sporocarps (Morton, 1988).
http://tolweb.org/Glomeromycota
Phylum Glomeromycota
• Only asexual reproduction is known in Glomeromycetes
• However, Glomus spp. express all known genes needed
for meiosis. Therefore, it is likely that sexual reproduction
is present in the life cycle of Glomero.
• The apical cell develops into a large spore (sporocarp)
blastically
• Glomeromycetes were previously classified as
Zygomycetes, hence the life cycle is likely similar
http://tolweb.org/Glomeromycota
Types of Mycorrhizal Association between Plants and Fungi
Endomycorrhizae
• A symbiotic relationship between Glomeromycete fungi w/ roots of
plants is called vascular / arbascular mycorrhiza (AM)
• The fungus penetrate the cell wall, producing arbascules & vesicles
w/in the cell
http://www.davidmoore.org.uk
http://mycorrhizas.info/
Types of Mycorrhizal Association between Plants and Fungi
Endomycorrhizae – arbascules and vasicles
http://mycorrhizas.info/
Some characteristic morphological features of glomeromycetes
A. Colonized roots of Plantago media with hyphae and spores of Glomus clarum .
B. Arbuscule of Glomus mosseae stained with chlorazol black.
C. Vesicle of Glomus mosseae .
D. Spore of Glomus sp. S328 showing the hyphal attachment.
E. Section of a sporocarp of Glomus sinuosum with spores grouped around a hyphal plexus and covered by a layer of hyphae.
F. Spore of Scutellospora cerradensis ,showing bulbous sporogenous cell and inner flexible walls with germination shield
(arrow). Inset: germination shield of S. scutata in face view.
G. Germinating spore of Gigaspora decipiens with sporogenous cell, warty germination layer and germination hypha.
H. Spore of Acaulospora denticulata with tooth-like wall ornamentations and inner germinal walls.
Images courtesy of Kerstin Wex (B, C), Fritz Oehl (F) and the American Society for the Advancement of Science (D).
Redeker & Raab. 2006. Mycologia 98: 885-895
ECM vs. AM Mycorhiza - Summary
http://mycorrhizas.info/
Phylum Zygomycota
Phylum Zygomycota
• The phylum contains 2 distinct classes:
– Zygomycetes: soil inhibiting moulds
associated with decayed food or animal dung
– Trichomycetes: associated with arthropods.
Possibly an obligate association
Phylum Zygomycota
• All zygomycetes have a coenocyte hyphae, lacking septa
• The cell wall is composed of chitosan and not chitin
• Species are primarily saprobs, soil inhibiting, plant debris inhibiting,
growing on decaying plants, fruits and vegetables
• Zygomycte species grown rapidly on most growth media or substrates.
• On 9 cm Petri plate with PDA at 25oC they will cover the entire surface in
less than 1.5 days including sporulation
Phylum Zygomycota
•
The most encountered zygomycetes belong to orders Mucorales &
Mortierelalles
•
On a daily basis we encounter Mucor spp. Or Rhizopus spp. on decaying
bread, fruits or vegetables at home
•
The species are characterized by long sporangiophores and aerial hyphae
Phylum Zygomycota
• Rhizopus spp. on decaying strawberry
http://groupprojects.bio.ed.ac.uk/image/rhizopus-shop-bought-strawberry
Phylum Zygomycota
•
Rhizopus spp.
•
Well encountered on decaying bread, fruits or vegetables at home
•
The species are characterized by short rhizoms that penetrate the
substrate, hence the name Rhizopus
•
It is a serious decay causing fungi in the supply chain of fresh produce,
which is difficult to control
Movie
https://www.youtube.
com/watch?feature=p
layer_detailpage&v=T
b6Fp2oHWGI
Phylum Zygomycota
• Rhizopus spp. – Asexual characteristics of Mucorales
• Asexual spores sporangiospores develop in sporangia on
porangiophores
• The sporangiophores are attached to the substrate by rhizoms, and to
each other by stolons
Phylum Zygomycota
• Rhizopus spp. – Asexual characteristics of Mucorales
http://www.blog.gurukpo.com/rhizopus
Phylum Zygomycota
• Rhizopus spp. – Asexual characteristics of Rhizopus
Mucoralesstolonifer
Prof. Lorry, M. Carris; Washington State University; www.apsnet.org
Phylum Zygomycota
• Sexual reproduction occurs between 2 mating types,
“MAT +” and “MAT –”
• sexual spores are called zygospores
Immature zygospore
http://faculty.baruch.cuny.edu/jwahlert/bio1003/fungi.html
Mature zygospore
Phylum Zygomycota
Life cycle of R. stolonifer
•
Mycelium and sporangiospores
are haploid (n)
•
Developing zygospore is
dikaryotic (n+n)
•
Zygospore is diploid (2n)
•
Meiosis occurs in zygospore
Phylum Zygomycota
Sexual reproduction occurs between 2 mating types, formation of zygospore
and zygosporangium
http://cronodon.com/images/toadstool_gill_vertical_section_labeled.jpg
Phylum Zygomycota
• Pilobolus spp. – dung fungi
• Cannon fungus – forcibly discharge spores
• Light sensing fungus
Phylum Zygomycota
• Pilobolus spp. – dung fungi
• Light sensing fungus – subsporngial retina cells aim the spornagium
towards the light
http://cronodon.com/images/toadstool_gill_vertical_section_labeled.jpg
http://herbarium.usu.edu/fungi/funfacts/pilobfct.htm
Phylum Zygomycota
• Pilobolus spp. – dung fungi
• Light sensing fungus – subsporngial retina cells aim the spornagium
towards the light
http://herbarium.usu.edu/fungi/funfacts/pilobfct.htm
Phylum Zygomycota
• Pilobolus spp.
• Cannon fungus –
forcibly discharge
spores
• Movie
https://www.youtube.com/watch
?v=b646LTmzTu8&feature=play
er_detailpage&list=PLIBN7tPGa
sRITpfVkCXLpAzf9_Y7_n6gv
Phylum Chytrodiomycota
Zoosporic fungi
Phylum Chytrodiomycota – “Chytrids”
• Evolutionary the most ancestral / primitive fungal phylum
• Approximately 900 identified species – saprobes & obligate parasites
• Prevalent in a wide range of aquatic and terrestrial habitats
• Mostly aquatic - need free water for reproduction
• Form a tube-like thallus lacking septa
• Form zoospores w/ a single posteriorly directed, whiplash flagellum
• most are saprobs, decomposing cellulose, chitin, and keratin as food
sources
• The name chytrids = “little pot”
• Image: thallus of Rhizophydium
http://www.bsu.edu/classes/ruch/msa/barr/4-15.jpg
Phylum Chytrodiomycota – “Chytrids”
• Chytrids form zoospores for reproduction in zoosporangia
• Zoospores lack a cell wall, having only a cell membrane
• Chytrids zoospores are uniflagelated, possesing a single,
posterior whiplash flagellum for movement in water
Allomycete zoospore
http://www.mycolog.com/chapter2b.htm
http://www.fungionline.org.uk/6asexual/3zoosp.html
Phylum Chytrodiomycota – Life Cycle
• Chytrids life cycle is a haplo-diplontic & is similar to plants more than
to fungi
• In this life cycle both the diploid (2n) and haploid (1n) phases are
multicellular
• The multicellular diploid (2n) phase is called Sporophyte. It produces
sporocytes in a sporangia. The sporocytes go through meiosis in the
sporangia, creating 4 haploid (n) zoospores
Zoosporangium and zoospores release of Chytridium lagenaria
Phylum Chytrodiomycota – Life Cycle
• The haploid (1n) zoospores disperse and germinate into a multicellular
haploid (1n) Gametophytes
• The gametophytes mature and produce a male (sperm) and female (eggs)
cells called in Gametangia (sing. Gametangium), in which sexual, haploid
(1n) zoosporic gametes develop
• The zoosporic gametes fuse, undergo fertilization and create a zygote (2n)
• The zygote develops into a multicellular diploid (2n) Sporophyte
• The sporophyte:
– Produces, via meiosis new haploid (1n) zoospores, which develop into new
gametophytes
– Produces diploid (2n) zoospores, via mitosis, which produce additional
sporophytes (the asexual stage?)
Phylum Chytrodiomycota - Life Cycle of Allomycetes
Phylum Chytrodiomycota - Allomycetes
• Allomyces spp. Gametangia: the female is paler and the male is
brownish
• The zoosporangium of Allomyces has opened and zoospores are
being explosively discharged to the surrounding medium
• The female secretes serinin, a pheromon that attract the male gametes
Phylum Chytrodiomycota - Allomycetes
Gametophyte
http://userwww.sfsu.edu/biol240/labs/lab_07lowerfungi/pages/allomyces.html
Phylum Chytrodiomycota – “Chytrids”
• A few chytrids are economically & ecologically important
pathogens
– Synchytrium endobioticum, causes black wart of
potato
– Olpidium is a vector of viruses causing big vain in
lettuce
– Batrachochytrium dendrobatidis is the frog chytrid that
has been implicated as a major factor in population
declines of frogs and other amphibians around the
world (Berger et al. 1998; Wake and Vredenburg
2008).
Phylum Chytrodiomycota - Synchitrium
• Synchitrium endobioticum – potato wart
• Zoospores infect immature potato tubers. Zoosporangia
develop within tubers cells producing wart and releasing
new zoospores
Phylum Chytrodiomycota - Synchitrium
•
•
Hypothetical life cycle of Synchitrium
“A” and “S” = asexual and sexual life cycle. Diploid and haploid stages = “2n” and “n.” 1. Discharge of
zoospores from mature thin-walled sporangia. 2. Dispersion of zoospores. 3. Encystment of zoospores
on host tissue. 4. Ingression of zoospores into host cells. 5. Growth of zoospores. 6. Development of
thin-walled sporangia. 7. Pairing up of zoospores. 8. Fusion of individual margins of zoospores. 9.
Fusion of opaque central bodies of zoospores. 10. Encystment of zygotes on host tissue. 11.
Development of encysted zygotes into young thick-walled sporangia. 12. Discharge of zoospores from
mature thick-walled sporangia.
http://palaeo-electronica.org
Phylum Chytrodiomycota – Olpidium
• Olpidium brassicae is an obligate pathogen of lettuce.
• It is a vector of the Lettuce Big Vain associated virus – Mirafiori
lettuce virus
Lettuce Big Vain symptoms
Olpidium brassicae in grass roots
zoosporangia and zoospores
http://vegetablemdonline.ppath.cornell.edu
http://archive.bio.ed.ac.uk/jdeacon/microbes/chytrid.htm
Phylum Chytrodiomycota - Rhizophydium
• Rhizophydium spp. are
both plant parasites and
saprobs
• As parasites they are
endoparasites
• The thallus has two
parts:
– An absorptive rhizomlike branching, lacking
nuclei or septa
– a multinucleated
zoosporangium
http://www.bsu.edu/classes/ruch/msa/barr/4-15.jpg
Phylum Chytrodiomycota - Rhizophydium
• The zoosporangia act as
gametangia & sporangis,
releasing zoospores
• Zoospores swim & attach to
plant hosts, encyst & release
their content into the plant cell
• New thalli develop
• Reports of sexual stages are
rare, but occur when 2
zoosporangia fuse and mix
their content
Rhizophydium infecting cianobacteria
Courtesy of Dr Gordon Beakes © University of Newcastle upon Tyne
https://www.uea.ac.uk/biological-sciences
Phylum Chytrodiomycota - Rhizophydium
http://protist.i.hosei.ac.jp
Summary
• Glomeromycetes are Arbascular Mycorhizae
• Zygomycetes are mostly saprobes of fruits,
vegetable and animel dung
• Chytridiomycetes are zoosporic aquatic fungi,
lacking hyphae, that may be saprobs or
andoparasitic fungi of plants and amphibians
• All have an unseptated thallus