Fungal Biotechnology
Lecture 6
Fungal Like Organisms
Dr. Nadav Nitzan
Chromista / Stramenopile
Phylum Oomycota
(Oomycetes – Water Moulds; ‫)פטריות ביצה‬
The Tree of Life
Eumycota = true fungi
Chromista = fungi-like
Genome Scale Eukaryotes Phylogeny –
Kingdom Chromista / Stramenopiles (“straw hair”)
Chromista
Keeling, Patrick, Brian S. Leander, and Alastair Simpson. 2009. Eukaryotes. Eukaryota, Organisms with nucleated cells. Version 28 October 2009.
The Tree of Life Web Project, http://tolweb.org/
Genome Scale Eukaryotes Phylogeny –
Kingdom Chromista / Stramenopiles
Groups of interests in Mycology & Plant Pathology
• Phylum Oomycota - cause plant diseases
• Phylum Labyrinthulomycota – rapid blight of turf
• Phylum Hyphochitridiomycota - parasites of fungi
Keeling, Patrick, Brian S. Leander, and Alastair Simpson. 2009. Eukaryotes. Eukaryota, Organisms with nucleated cells. Version 28 October 2009.
The Tree of Life Web Project, http://tolweb.org/
Oomycota
• Oomycetes, (water moulds) include ~ 800 species
• Most are saprobs or parasitic on plants & animals
• The name Oomycetes refers to the sexual resting spore, known as
oospores (an “egg” spore)
• All Oomycetes produce a mycelium similar to fungi
• Oomycetes mycelia are coenocytes, lacking septa
• Oomycetes reproduce by zoospores, therefore develop on hosts in
the presence of free water
• The vegetative nuclei are diploid (2n) – dominant ploidy in life cycle
• The cell wall consists of cellulose
• The cell membrane lacks sterols (no Ergosterol)
Oomycota
•
Oomycetes cause root diseases and foliar diseases of plants, as well as
diseases in vertebrates
•
The foliar diseases of plants are known as Downey Mildews
•
Oomycetes cause some of the most devastating plant disease, such as
potato late blight, grape downey mildew and sudden oak death
•
Phytophthora infestans is the most influential Oomycete in human
history. It is the cause of potato late blight, which resulted in the great
Irish famine in the 1860’s, w/ the death of ~1 million and the emigration of
1.5 million to North America. It was also one of the causes for the end of
world war 1
Classification in phylum Oomycota
• Order Saprolegniales
• Order Leptomitales
• Order Leginidiales: parasites of plants & animels
– Lagenidium giganteum: a parasite of mosquitoes w/
economical importance
• Order Peronosporales: the most specialized. Include
saprobs and pathogens of aquatic & terrestrial plans &
animals
Phylum Oomycota / Order Peronosporales
• Family Pythiaceae
– Pythium spp.: cause root diseases in plants
– Phytophthora spp.: cause root & foliar diseases in plants
• Family Peronosporaceae – Downey Mildews
– Plasmopara viticula – Downey mildew of grape
• Family Albuginaceae – white rusts
– Albugi candida
Oomycetes reproduction
Generalized life cycle of
Oomycetes
• Nuclei are diploid (2n),
excluding the production
of sexual gametes
(meiosis)
http://www.fungionline.org.uk/1intro/5importance.html
Oomycetes – asexual reproduction
• Asexual reproduction is via hyphal expansion and branching, which
also develop zoospores
• Pythium spp. developing on bean pod
ttp://agdev.anr.udel.edu/weeklycropupdate/wp-ontent/uploads/2009/09/LimaPythium.jpg
Oomycetes – asexual reproduction
Mycelium of Pythium spp. lacking septa (coenocyte)
T.W. Allen; www.apsnet.org
Oomycetes asexual reproduction – zoospores
•
Oomyctes reproduce by the production of biflagellated zoospores.
•
Zoospores are wall-less
•
The tinsel flagellum has lateral branches, and it pulls the cell forwards
•
The whiplash flagellum is smooth, directed backwards and pushes the cell forwards
•
Zoospore have a large spherical lipid droplet at the rear, which may act as a buoy
and as fuel/energy store
Sporangium and zoospores of P. megakarya; https://www.plantmanagementnetwork.org/pub/php/review/cacao/
Oomycetes – zoospore & asexual reproduction
• The sporulating mycelium produces
a zoosporangium in which
zoospores develop
• The sporangium may develop on a
sporangiophore (like conidiophores
in ascomycetes)
• The zoosporangium is divided from
the parent hypha by a cross-wall.
The nuclei in it cleave to become
single zoospores
• The zoospores emerge from the
zoosporangium, infect roots or
leaves and develop into a
mycelium
Oomycetes – zoospore & asexual reproduction
Zoosporangia of Phytophthora cinnamomi releasing zoospores
(Photo by Ratiya Pongpisutta and Brett Summerell, Australia, www.apsnet.org
MOVIE: https://www.youtube.com/watch?v=gDT5Pg3_nsM&feature=player_detailpage
https://www.youtube.com/watch?feature=player_detailpage&v=PxF8OwDtJh0
Sporangiophore
Oomycetes – zoospore & asexual reproduction
Movies:
• https://www.youtube.com/watch?v=gDT5P
g3_nsM&feature=player_detailpage
• https://www.youtube.com/watch?feature=p
layer_detailpage&v=PxF8OwDtJh0
Oomycetes – zoospore & asexual reproduction
• Zoosporangia of Phytophthora infestans w/ developing zoospores on
sporangiophores
• In some cases (temperature dependant) zoosporangia may germinate
directly into hyphea w/o producing zoospores
• Zoosporangia of Phytophthora spp. are lemon shaped
• Photo by R. V. James and W. E. Fry, www.apsnet.org
Oomycetes – sexual reproduction
• Sexual reproduction occur when 2 mating types – A1 & A2
meet, transfer gametes and form an Oospore
• Oomycetes are homothallic, but some are heterothallic
• Phytophthora spp. may be homothallic or heterothallic
• Phytophthora infestans is heterothallic
• Pythium spp. are homothallic, but out-crossing may occur
• Peronospora spp. are homothallic, but out-corossing may
occur
Oomycetes – sexual reproduction
• Sexual reproduction initiates when hyphae gametangia - female organs
(oogonia / oogonium) and male organs,
(antheridia / antheridium) at their tips
• Meiosis & ploidy reduction (2n >> 1n) occur in the oogonia & antheridia
• The oogonium is globes & larger than the anteridium. It contains several
non-motile eggs (ova; 1n)
• The anteridium is elongated and contains several non-motile male nuclei
(sperms; 1n)
www.apsnet.org
Oomycetes – sexual reproduction
• The female hyphae release a hormone called antheridiol, which
stimulates the development of male antheridial branches
• The male hyphae release a hormone called oogonial which induces
oogonia development in the female hyphae
• The male hyphae are attracted to the oogonia
www.apsnet.org
Oomycetes – sexual reproduction
• Upon contact between the
antheridium and the oogonium, one
or more fertilization hyphae grow
into the oogonium toward one or
more eggs
• The sperm (male nuclei) moves
through the fertilisation hyphae
and fertilizes the egg
• Usually, several antheridia fertilize
the eggs in a single oogonium
• Each egg is fertilized once
Oomycetes – sexual reproduction
• Nuclei fusion occurs within the oogonium, producing a diploid
nucleus
• The fertilized egg produces a thick wall around itself, becoming a
resting oospore
• The oospore can withstand cold and dry conditions, buy seems to
be sensitive to hot temps’ >45oC
• Following a dormancy the oospore germinates to produce a
zoosporangium and new asexual zoospores. A new life cycle
begins
A germinating oospore of P. infestans
producing zoosporangium
Fry & Grunwald, www.apsnet.org
Oomycota - Pythium spp.
Oomycetes – Pythium spp.
•
Soil & seed-borne pathogen
•
Saprobs and pathogenic to plants
•
Primarily homothalic, but outcrossing may occur
•
Cause root rot, dumping-off and blight in a wide variety of plants
Onion root rot, cased by Pythium spp.
Oomycetes – Pythium spp.
Phytium blight on turf grass
www.apsnet.org
Oomycetes – Pythium spp.
Life cycle of Pythium on turf grass
Oomycetes – Pythium spp.
Pythium spp. zoospores released out of zoosporangia
(P.B. Hamm; www.apsnet.org)
Oomycetes – Pythium spp.
Club-shaped antheridia of Pythium attaching to an oogonium. Both the
antheridia (arrows) and the oogonium were borne on the same hypha.
Note the fertilization tube from each of the antheridia. (Courtesy of T.W.
Allen; www.apsnet.org).
Oomycetes – Pythium spp.
Pythium oospores in leaf tissue. Notice thick cell wall
(Courtesy L.L. Burpee, NCSU; www.apsnet.org)
Oomycota - Phytophthora spp.
Oomycetes – Phytophthora spp.
• 123 formally described species (http://www.phytophthoradb.org/species.php)
• Phytophthora = plant destroyer
• May be homothallic or heterothallic
• All are saprobs & cause serious diseases in plants
• Produce mycelium, zoospores, oospores and some produce
chlamidospores
• Growth temp’ ranges from 2oC to 36oC, pending on species
• Well known species are:
– P. infestans – Source: potato. Cause late blight on potato
& tomato
– P. cinnemoni: Source: cinnamon. Cause canker in trees
– P. capsici: Source: pepper (Capsicum). Cause blight, rot &
wilt in tomato, pepper & cucurbits
– P. cactorum: Source: cacti. Cause crown rot in trees
– P. ramorum: Cause Sudden Oak Death
Oomycetes - Phytophtora infestans
•
Possibly the most devastating
plant pathogen in human history
•
Causes Late Blight (‫)כמשון‬
•
The biological cause of the
Irish Potato Famine
•
Infect leaves, stems and tubers
•
Survive in soil, w/ air or soil-borne
dissemination of zoospores
•
Downey-like sporulation on leaves
•
Preferred conditions are cloudy,
rainy weather w/ cold – cool
temps. ~200C
•
Zoosporangia are lemon shaped
Oomycetes - Phytophtora infestans
The life cycle of P. infestans on potato (www.apsnet.org)
Oomycetes - Phytophtora infestans
A potato field infected by P. infestans demonstrating late blight symptoms
http://www.plantpath.cornell.edu/Fry/Disease12.html
Oomycetes - Phytophtora infestans
Late blight symptoms on potato foliage due to P. infestans infection
http://www.longislandhort.cornell.edu/vegpath/photos/images/potatolb_sporescux1200.jpg
Oomycetes - Phytophtora infestans
Downey mildew like sporulation of P. infestans on potato leaf
http://www.longislandhort.cornell.edu/vegpath/photos/images/potatolb_sporescux1200.jpg
Oomycetes - Phytophtora infestans
P. infestans: zoosporangia downey-like sporulation
(from Fry Lab; http://www.plantpath.cornell.edu)
Oomycetes - Phytophtora infestans
Lemon shaped zoosporangia of P. infestans
(from Fry Lab; http://www.plantpath.cornell.edu)
Oomycetes - Phytophtora infestans
Rotted potato tubers due to P. infestans infection
http://www.longislandhort.cornell.edu/vegpath/photos/images/potatolb_sporescux1200.jpg
Oomycetes - Phytophthora ramorum
Sudden Oak Death
(J. Park; www.apsnet.org)
Oomycetes - Phytophtora ramorum
• Disease: Sudden Oak Death
• Right: lesion w/in tree
• Below: sap bleeding from bark
http://www.acgov.org/cda/awm/agprograms/pestexclusion/suddenoakdeath.htm
Oomycota - Downey Mildews
‫כשותיות‬
Oomycetes – Downey Mildews
• Obligate parasites
• Destructive foliar diseases of plants
• Zoospores penetrate leaves & infect plants via stomata
• Zoosporangia produce a fuzzy sporulation on the
under side of the leaf, exiting the leaf via stomata
• Spornagiophores are dichotomously branched
Oomycetes – Downey Mildews
Dichotomously branched sporangiophore and lemon-shaped sporangia
of Pseudoperonospora cubensis (G. J. Holmes; www.apsnet.org)
Oomycetes – Downey Mildews
Lemon shaped zoosporangia borne at the tips of dichotomously branched
sporangiophores of Pseudoperonospora cubensis (Downey mildew of
cucurbites) (S. J. Colucci; www.apsnet.org)
Oomycetes – Downey Mildew of grape
Plasmopara viticula causing downey mildew of grape
(www.apsnet.org)
Sporulation on abaxial side of leaf (up)
Early and advanced symptoms (right)
Oomycetes – Downey Mildew of grape
Plasmopara viticula causing downey mildew of grape
(www.apsnet.org)
Sporulation on berries
Oomycetes – Downey Mildew of grape
Plasmopara viticula causing downey mildew of grape
(www.apsnet.org)
Decay of berries due to
downey mildew infection
Oomycetes – Downey Mildew of grape
Life cycle of Plasmopara viticula on grape
Similarities between fungi & Oomycetes
Oomycetes
Fungi
Reproduce sexually & asexually
Produce mycelium
Saprobs, facultative and obligate parasites
Attack plants and animels
Dissimilarities between fungi and Oomycetes
Oomycetes
Fungi
Spores
Zoospores w/ 2 flagella
Non-flagelated spores or
zoospores w/ 1 flagellum (chytrids)
Cell wall
cellulose
chitin
Membrane
Lack sterols
Ergosterol
Life cycle
Diploid (2n)
Haploid (1n) or dikaryotic (n+n)
Mycelium
Non septated,
coenocyte
Septated (excluding chytrids &
zygomycetes)
Chromista / Stramenopile
Phylum Labyrinthulomycota
Genome Scale Eukaryotes Phylogeny –
Kingdom Chromista / Stramenopiles (“straw hair”)
Groups of interests in Mycology & Plant Pathology
• Phylum Labyrinthulomycota –
Rapid blight of turf
Keeling, Patrick, Brian S. Leander, and Alastair Simpson. 2009. Eukaryotes. Eukaryota, Organisms with nucleated cells. Version 28 October 2009.
The Tree of Life Web Project, http://tolweb.org/
Phylum Labyrinthulomycota
• Labirintula spp. are associated with marine systems and increased
salinity (3.5-4.0 dS/m). It was first identified on turf in California in
1995. Today it is present in 11 states in the USA on turf, possibly
due to irrigation with saline water
• Species are saprobs and can be cultured on specialized media
Phylum Labyrinthulomycota
• Labirintula develop vegetatively by clump cells
• Cells are motile, hyaline and ellipsoid or spindle shaped
• Sexual stages are very rare, but produce zoospores
• The cells form a slimy, ectoplasmic network in which cells
move, a.k.a “slimeway”
Colony of motile Labyrinthula terrestris cells in ectoplasmic networks.
Photo courtesy of Donna Bigelow and Mary Olsen; www.apsnet.org .
Phylum Labyrinthulomycota
Labyrinthula terrestris cells in culture, on the surface of the agar
medium. Photo courtesy of K. K. Yadagiri; www.apsnet.org
Phylum Labyrinthulomycota
Labyrinthula terrestris cells surrounded by tubular ectoplasmic networks. The ovoid hyaline
structures inside the cells are nuclei, each containing a dark nucleolus; a single nucleus is
visible in each cell. Cells are approximately 14-16 × 5-6µm in size.
Photo courtesy of Paul Peterson and Bruce Martin; www.apsnet.org
Phylum Labyrinthulomycota
Infected grass blades on selective media from which Labyrinthula terrestris cells have
emerged. Note the characteristic labyrinth, forking, or digitate shape of colony growth
and slimy appearance. The clumped cells may be mistaken for yeasts or bacteria, but
the growth form is distinctive of Labyrinthula. Photos courtesy of K. K. Yadagiri.
Colony is maze-like
(labyrinth)
Phylum Labyrinthulomycota
Disease cycle of rapid blight caused by Labyrinthula terrestris
Photo courtesy of Bruce Martin; www.apsnet.org
Protozoa
Slime Moulds
‫פטריות ריר‬
The Tree of Life & Fungal Phylogeny
Eumycota = true fungi
Chromista = fungi-like
Myxomycota = slime molds
Genome Scale Eukaryotes Phylogeny & The Fungal Kingdom
Eumycota
Myxomycota
Keeling, Patrick, Brian S. Leander, and Alastair Simpson. 2009. Eukaryotes. Eukaryota, Organisms with nucleated cells. Version 28 October 2009.
http://tolweb.org/Eukaryotes/3/2009.10.28 in The Tree of Life Web Project, http://tolweb.org/
Slime Moulds
• Slime molds are organisms that have a feeding stage in
their life cycle that lacks a cell wall
• They may be uninucleate (amoeba) or multinucleate
(plasmodium)
• The lack of a cell wall facilitates engulfment of food, in
contrast to true fungi that must absorb their nutrients through
a cell wall
Slime Moulds
Amebozoa
Plasmodial
slime moulds
(Myxomycota)
Cellular
slime moulds
(Dictiosteliomycota &
Acrasiomycota)
Cercozoa
Endoparasitic
slime moulds
Plasmodiophoromycota
Plasmodial slime molds - Myxomycota
• The plasmodial slime molds are commonly found in
temperate forests on tree bark, plant litter etc.
• The plasmodium moves over and through decaying
organic matter
• It feeds by engulfing bacteria, fungi, and other
microorganisms
• They produce a plasmodium, a multinucleate
(coemocyte) feeding stage, lacking a cell wall called
• Nuclei in the coenocytic plasmodium are 2n
Plasmodial slime molds - Myxomycota
• The most eye-catching stage of the plasmodial slime
mold is the fruiting structures, called sporophores
• The sporophores are often brightly colored and visible to
the naked eye
• One of the most common slime molds in temperate
regions is Fuligo septica, a.k.a “dog vomit slime"
• The plasmodial slime molds are not plant or animal
parasites and have no known economic importance
• They are used as model organisms for research
Plasmodial slime molds - Myxomycota
Feligo septica
http://commons.wikimedia.org/wiki/File:Fuligo_septica_LC0115.jpg
Plasmodial slime molds - Myxomycota
Physarum spp.
Plasmodial and sporulation stages
Plasmodial slime molds - Myxomycota
http://classes.midlandstech.edu/carterp/Courses/bio225/chap12/ss4.htm
Plasmodial slime molds - Myxomycota
https://www.youtube.com/watch?feature=player_detailpage&v=GY_uMH8Xpy0
Physarum spp.
http://discovermagazine.com/2009/jan/071; Image courtesy of Toshyuki Nakagaki
Cellular slime molds - Dictyostelida
• Cellular slime molds are unique
“social” amoeba
• Each amoeba live individually in
temperate forests and feed on
microorganisms
• When food sources diminish they
release signal molecules into their
environment that cause them to gather
into a multicellular slug
Cellular slime molds - Dictyostelida
• They grow into a “sluggish creature” forming a single fruiting body
• Some of the amoebae become spores and disseminate, while the
rest become the fruiting bodie’s stalk and die
• Cellular slime mold do not form a coenocyte plasmodium
Dictyostelium spp.
http://www.ncbi.nlm.nih.gov/genome?term=dictyostelium%20discoideum
Cellular slime molds
Life cycle of cellular slime moulds
https://www.youtube.com/watch
?feature=player_detailpage&v=
bkVhLJLG7ug
Endoparasitic slime moulds - Plasmodiophoromycota
• Members of the phylum are obligate parasites
• They produce the plasmodial stage inside the cells of
plants, algae, diatoms, and Oomycetes
• In agriculture, members of this phylum are economically
important plant parasites
– Plasmodiophora brassicae, causes clubroot of crucifers
– Spongospora subterranea, causes powdery scab of potato and
transmits the mop-top virus of potato
Endoparasitic slime moulds - Plasmodiophoromycota
• Plasmodiophorides produce cysts inside host cells
• The cysts are released from the plant tissue and germinate,
releasing a primery zoospore
• The primary zoospore infects the host by injecting its cytoplasm into
a host cell
• Infected host tissue enlarges and a plasmodium develops with in
• The coenocyte plasmodium cleave into zoosporangia with in the
tissue. It produces secondary zoospores and resting-spors
(sporosorii)
• The secondary zoospores continue to infect new host cells
• The sporosorii become the over-wintering survival structure from
which primary zoospores are released
Endoparasitic slime moulds - Plasmodiophoromycota
Life cycle of Plasmodiophora brassicai – clubroot of crucifers
Movie
https://www.youtube.com/watch?fea
ture=player_embedded&v=3dyQhs
qIu0o
http://www.gov.mb.ca/agriculture/crops/plant-diseases/clubroot-brassica.html
Endoparasitic slime moulds - Plasmodiophoromycota
P. Brassica
Infected root & resting spores
within root tissue
http://archive.bio.ed.ac.uk/jdeacon/FungalBiology/chap2_6i.htm
Endoparasitic slime moulds - Plasmodiophoromycota
Spongospora subterranea – potato powdery scab
Postules on tuber & galls on roots
Endoparasitic slime moulds - Plasmodiophoromycota
Spongospora subterranea – potato powdery scab
All images by Ueli Merz
Sporosori
Zoosporangia w/in root hairs
Plasmodium w/in root hairs
zoospore