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