fig. 12 - · pdf fileeukaryotic microbial diversity fig. 12.1. phylogeny of the eucarya. note...
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LECTURE 16
EUKARYOTIC MICROBIALDIVERSITY
Fig. 12.1. Phylogeny of the Eucarya. Note the
distribution of
Algae, Fungi and Protozoa
Phycology is the study of algae.
Algae have chlorophyll a and use oxygenicphotosynthesis.
ALGAE
Algae encompass many diverse groups:
I. Green algae (Chlorophyta)II. Euglenoids (Euglenophyta)III. Golden-Brown + Diatoms
(Stramenophiles)IV. Brown Algae (Phaeophyta)V. Red Algae (Rhodophyta)
VI. Dinoflagellates (Pyrrophyta)
Fig. 12.03Fig. 12.3. Note
that algae are not
monophyletic and
are mixed in with
the “Protozoa”,
there may have
been several
jumps of
chloroplasts
(cyanos) into
eucs….
Classification based on many propertiesincluding:
• chlorophyll molecules
• flagella
• reproductive structures
• life histories
• and others
I. Green Algae - Chlorophyta
• have chlorophylls a and b
• wide variety of forms
• both sexual and asexual reproduction
• closely related to land plants
Complex life cycle - sexual and asexual
Reproduction in ChlamydomonasII. Euglenoids (“photosynthetic protozoa”)
• have chlorophyll a and b
III. Golden-Brown and Diatoms - Chrysophyta
• diatoms have a 2-piece cell wall of silicacalled a frustule
Diversity of Diatoms
VI.Dinoflagellates - PyrrhophytaFig. 12.6
• alveolate algae – related to Ciliates (Protozoa)
• some are bioluminescent
• may cause red tides
• some are symbionts in other marine organisms,especially corals – called zooxanthellae.
PROTOZOA
Protozoology is the study of protozoa.
Not a monophyletic group – defined as amotile, eukaryotic unicellular cell.
Fig. 12.07
Fig. 12.7Protozoa arehighlighted inred….not amonophyleticgroup.
Most are chemoheterotrophic.
!ingest solid nutrients via phagocytosis
!ingest soluble nutrients and smallsolids via pinocytosisAlso can take up small nutrients viadiffusion
See Figure 3.50……
Some can encyst – form resting stage or cyst.
1) help protist survive harsh periods
2) allow for transfer of parasites
between hosts
Feeding or vegetative stage is called atrophozoite.
Figure 12.9.
Polymorphic
lifecycle of a
protozoan,
Naegleria.
A. Ameboid stage in
animal tissue or
soil.
B. Flagellated stage in
water
C. Cyst under drying
conditions…..
Protists move via:
1) pseudopodia (“false feet”) – cytoplasmic
extensions
2) flagella
3) cilia
Reproduction in protists is via:
1) binary fission.
Fig. 12.10. Variations on asexual
reproduction in protozoa
2) sexual reproduction - e.g. conjugation
common among Paramecium. Manydisease causing protists have a sexualcycle…
Many groups, we’ll concentrate on 3:
I. Sarcomastigophora
II. Apicomplexa
III. Ciliates
I. Phylum Sarcomastigophora
• flagella – subphylum Mastigophora
• pseudopodia – subphylum Sarcodina
Mastigophora contains important groups:
!Giardia
Fig. 24.22. Giardia lamblia trophozoites in human intestines.
!Trichomonas
!trypanosomes
Table 24.13Sarcodina – amoeboid protists
! some have test = “shell” – provides
protection
! Foraminiferans = marine amoebae
with ornate tests
! Many are symbiotic
II. Apicomplexa
• have a spore-forming stage in their life cycle
at some point
• generally lack locomotory organelles
• all are parasites – includes some of most
important parasites:
! Plasmodium –malaria
! Toxoplasma
! Cryptosporidium
III. Ciliates ( Phylum Ciliophora)
-Major predators of bacteria in natural systems
-Have 2 nuclei
-Transverse binary fission (figure 12.10)
Fig. 1.8……
• move with cilia Fungus = eukaryotic, spore-bearing organisms
with absorptive nutrition, no chlorophyll, and
that reproduce both sexually and asexually.
Mycology = the science of studying fungi
The Fungi
Fig. 12.11. Sequence
based phylogeny of the
fungi…….
Some general fungal terms:
Mycelium = many hyphae
Chitin = the glycoprotein that makesup a fungal cell wall (polymer of N-acetylglucosamine)
Where else do you find chitin??
Saprophytes = nutrients come from dead material(decomposers, chemoheterotrophs)
Many fungi are mutualists with plants (mycorrhizae)and cyanobacteria or algae (lichens)…
Mold = filamentous - long, branched filaments orhyphae. Together, hyphae form a mycelium.
• coenocytic = continuous, no cross walls
• septate = cross walls, with pores
Figure 12.13. Yeast = unicellular fungus
Dimorphic fungi - alternate between yeast form
and mold forms - the YM shift
Common in pathogenic fungi, but
with opposite patterns in animal vs.
plant hosts
• Animals - yeast in host, mold in
environment
• Plants - mold in host, yeast in
environment
Fungal reproduction
Asexual or sexual
Asexual
1. Divide into 2 equal cells- binary fission
2. Budding Fig. 12.14. Asexual reproduction
(budding) in a yeast….
3. Form asexual spores (conidia)
4. Fig. 12.15 . Asexual reproduction
in a filamentous fungus
Fungal reproduction
Sexual
- the union of compatible nuclei
• haploid gametes
• gamete-producing bodies
• hyphae
Major Fungal Divisions
(based on DNA sequencing)
I. Zygomycota
II. Ascomycota
III. Basidomycota
IV. Chytridomycota
I. Zygomycota
• examples - bread mold, arbuscularmycorrhizae
• hyphae are coenocytic (no or few cross walls)
• sexual reproduction produces zygospores
Fig. 12.16. B. Rhizopus stolonifer, black bread mold
EndoMycorrhizae
Endomycorrhizae are
Zygomycetes and are
associated with over 70%
of land plants - also
called arbuscular
mycorrhizae
<--- arbuscule inside plant root cell
II. Ascomycota
• example - food molds,mildews, cup fungi, morels,some ectomycorrhizae,many types of yeast….
• characteristic reproductive structure -
ascus
Very common in soils many forms have
never been grown in the lab several large
new groups (at the class and sub-phylum level) of
fungi discovered (Science 301: 1359-1361 (2003)).
• mycelia are septate
Phylogenetic tree of all fungi
(based on LSU rDNA)
Green branches are groups found in tundra
soils.
A = Ascomycetes
Clade I = mostly summer
Clade II = mostly winter and spring
Clade III = spring and summer
B = Basidiomycetes
(Schadt et al. Science 301: 1359-1361)
Summer
clade
Winter &
snow-melt
clade
III. Basidiomycota
• examples are shelf fungi and mushrooms
• form a basidium
Fig. 12.12. Some sexual fruiting bodies of Basidiomycestes.
B. A shelf fungus growing on wood. C. Amanita muscaria
an ectomycorrhizal fungus…….
Figure 12.17. The structure of a typical Basidiomycete
Note button stage, underground hyphal network,
gills and basidia on the gills….
Sexual life cycle of a Basidiomycete…..
EctoMycorrhizae
"Ectomycorrhizae are mostly
Basidiomycetes - many of the large
mushrooms in forests are the sexual stage of
ectomycorrhizal fungi….
V. Chytridomycota - the chytrids
• asexual stages are motile zoospores – have
flagella
• important in that they have been implicated
in the devastation of frog populations
worldwide.
SLIME MOLDS
• resemble fungi in their appearance and
lifestyle
• phylogenetically distinct from fungi
Fig. 12.1. Phylogeny of
the Eucarya.
Note the distribution of
Slime Molds and
Oomycetes
-no longer considered
to be fungi….
Acellular Slime
Molds Figure 12.20
Eukaryotic microbes and food…..
Bread Production
Along with cheese, bread is one of the most ancient
foods.
Here, yeasts grow more aerobically {Saccharomyces (an
ascomycete) is a facultative anaerobe}, which makes
more CO2 and less alcohol…… The alcohol that is formed is
evaporated off during cooking…
Bakers will add enough yeast to allow the dough to rise
in 2 hours or less.
To make sourdough breads both a yeast and
Lactobacillus bacteria are used to give them
their acidity and flavor