Diversity of prokaryotes In morphology In habitat In metabolism Basics of metabolism:

1. Diversity of prokaryotes In morphology In habitat In metabolism Basics of metabolism: energy source (of electrons, ultimately used for ATP synthesis) electrons are eventually transferred to a terminal electron acceptor (oxygen for us) many prokaryotes can use different terminal electron acceptors

2. Where does the energy (i.e., electrons) come from? Some organisms use sunlight; can use CO2 to make sugar: phototrophs Other organisms use organic sources (like sugar!): heterotrophs Prokaryotes can be classified further based on carbon source and energy source

3. Aerobes- terminal electron acceptor is oxygen most efficient Anaerobes- inorganic molecule is terminal electron acceptor (e.g., S, SO4-, NO3- or NO2-) less efficient than aerobic respiration Fermenters- use organic molecule as terminal electron acceptor least efficient

4. Some organisms use organic material for energy: organotrophs Some use inorganic material: lithotrophs Anaerobic lithotrophs may have been among the earliest on Earth

5. Where do anaerobic environments exist today? Soils: aerobes consume existing oxygen Aquatic environments Various internal environments Obligate anaerobes are killed by oxygen

6. Anaerobic chemolithotrophs Oxidize inorganic molecules like hydrogen gas (and produce what?) Use carbon dioxide or sulfur as electron acceptor Methanogens- produce methane and water grow in sewage, intestinal tracts, etc. Hard to culture, but may be a significant alternative energy source

7. Anaerobic chemoorganotrophs Eubacteria- high-sulfur-content mud often found in “communities” with other bacteria help cycle sulfur- what is its use in the environment? how do we know when sulfur is being metabolized? Archaea: hyperthermophiles

9. Anaerobic chemoorganotrophic fermenters: Do NOT use Krebs cycle or electron transport in ATP synthesis End products vary among species Clostridium- ferment many compounds and produce many different end products obligate anaerobes Lactic acid bacteria- OBLIGATE fermenters; produce lactic acid even if oxygen is present Streptococcus, Lactobacillus, etc.

11. Lactobacillus, Lactococcus important in commercial fermentation processes Yeast- bread, beer, wine Lactose fermenters- cheese, yogurt Propionibacterium- also used in cheese produciton; makes CO2 (like yeast)

12. “anoxygenic phototrophs” Usually found in aquatic habitats shallow enough to obtain light for energy do NOT use water as electron source; therefore do not produce oxygen Bacteriochlorophyll absorbs wavelengths of light that penetrate water Purple sulfur bacteria use H2S Purple nonsulfur bacteria do not; more diverse metabolically (and in habitat) Pigments contained within cell membrane

13. Green bacteria pigments contained within chlorosomes sulfur and non-sulfur forms Can also grow in the dark Other such organisms have been found, but are harder to observe Winogradsky columns are useful

14. Oxygenic phototrophs: cyanobacteria Essential as “primary producers” Morphologically diverse- shapes, mobility, presence of sheaths, etc. Contain chlorophyll and psychobiliproteins to harvest energy from light Nitrogen-fixing cyanobacteria fix N2 as well as CO2 from the atmosphere Enzyme is contained within a protective heterocyst

16. Heterocyst protects enzyme from oxygen

17. Overgrowth of cyanobacteria can produce nuisance “blooms” Algae can do this, too

18. Aerobic chemolithotrophs Oxidize sulfur, nitrogen, hydrogen Sulfur oxidizers: generate H2SO4 may be filamentous or unicellular contribute to “acid runoff” (Thiobacillus) some can oxidize other metals Nitrifiers- help cycle nitrogen in soil oxidize ammonium, nitrite (nitrate is less toxic, can be taken up by plants)

19. Aerobic chemoorganotrophs some are ubiquitous, some are specialized May be obligate aerobes or facultative anaerobes Obligate aerobes cannot ferment molecules for energy Micrococcus, Mycobacterium, Pseudomonas Thermus- extremophile Deinococcus- radiation- resistant

20. Facultative anaerobes Corynebacterium (genus) Enterobacteriaceae (family)

21. How do bacteria survive in so many different environments? Resistance stages endospores (Clostridium, Bacillus) soil bacteria cysts (Azotobacter) nitrogen fixers fruiting bodies (Myxobacteria) decomposers filaments (Streptomyces) produce antibiotics

22. Aquatic bacteria- nutrients are scarce Sheathed, swarmers attachment; movement to a more favorable location Caulobacteria, Hyphomicrbium- specialized attachment

23. “Parasitic” bacteria Bdellovibrio

24. Bioluminescent bacteria Emit light- when enough bacteria are present WHY?? Symbiotic?- host provides nutrients; it provides some advantage (squid, flashlight fish) Legionella- can inhabit protozoa found in ventilation systems

25. Bacteria and their animal hosts On skin- Staphylococcus On mucous membranes respiratory- Streptococcus, Lactobacillus many reside in GI tract (How do they get there?) Many organisms of diverse morphology and microenvironment

26. Obligate intracellular parasites Lack full biosynthetic capacity Rickettsia (vector-borne: ticks, lice) Coxiella (shed by one animal, inhaled by another). May also be vector-borne Chlamydia (person-to-person contact) unusual physical and growth features

27. Archaea- “extreme” bacteria Euryarchaeota- methanogens; extreme halophiles (salt-loving bacteria) membranes contain bacteriorhodopsin (enables them to obtain energy from sunlight) Crenarchaeota- both groups contain extreme thermophiles some generate methane some reduce sulfur some are thermophilic acidophiles

28. Summary: bacteria can be found just about anywhere on Earth! we sue this information to help identify microorganisms Questions about: evolution (when did they appear; what can they tell us about conditions on ancient Earth?) their role in maintaining ecological balance metabolic products of interest colonization of living organisms; pathogenesis; treatment