Survey of the Microbial World

1. Survey of the Microbial World Unit 3: 5 days

2. February 24thand 25th: Prokaryotes • Important manuals divide bacteria based on several criteria: • Gram stain reaction • Cellular morphology • Oxygen requirements • Nutritional properties • Many rRNA discoveries are helping to classify bacteria better

3. Classification • Three major domains:

4. Archaea • Highly diverse with respect to morphology, reproduction, physiology, and ecology • Grow in extreme habitats • Anaerobic • Hypersaline • High temps

5. Archaea • Cell walls do not contain peptidoglycan • Differ from bacterial cell walls in structure • Membrane lipids have branched chain hydrocarbons connected to glycerol by ether links • Bacteria and eukaryotes have glycerol connected to fatty acids through ester bonds

6. Archaea • Some can synthesize methane • Have unique glucose catabolism and pathways for CO2 fixation • Have distinguishable tRNA, ribosomes, elongation factors, and RNA polymerases

7. Archaea • Five major types: • Methanogenicarchaea • Sulfate reducers • Extreme halophiles • Cell wall-less archaea • Extreme thermophiles • Two official phyla: • Crenarchaeota • Euryarchaeota

8. Crenarchaeota • Extremely thermophilic • Sulfur metabolizers • Frequently acidophiles • S may be used as an electron acceptor in anaerobic respiration, or as an electron donor for lithotrophs • Most are strict anaerobes • Found in geothermally heated soil and water that is rich in sulfur

9. Euryarchaeota • Contains 5 major groups: • Methanogens • Halobacteria • Thermoplasms • Extreme thermophilic S metabolizers • Sulfate reducers

10. Methanogens • Strict anaerobes • Obtain energy through synthesis of methane • Several unusual cofactors involved in methanogenesis

11. Halobacteria • Aerobic chemoheterotrophs • Require at least 1.5 M NaCl for growth • Found in salt urns, salt lakes, and salted fish • Halobacteriumsalinarium can carry out photosynthesis without chlorophyll (uses a different pigment)

12. Thermoplasma • Thermophilic • Grows in hot, acid coal refuse piles • Survives even without a cell wall • Picrophilus can grow at pH 0

13. Thermococci • Extremely thermophilic organisms • Can reduce sulfur to sulfide

14. Sulfate Reducers These archaea are being used to clean heavy metal waste from nuclear reactors • Many extreme thermophiles • Some use a variety of electron donors to reduce sulfate

15. Bacteria • Four major divisions: • The Deinococci and Nonproteobacteria Gram Negatives • The Proteobacteria • The Low G and C Gram Positives • The High G and C Gram Positives

16. Deinococci and Nonproteobacteria Gram Negatives • Order Deinococcales: • Aerobic • Gram positive • Cocci and rods • Unusually high resistance to desiccation and radiation Deinococcusradiodurans

17. Deinococci and Nonproteobacteria Gram Negatives • Photosynthetic bacteria: • Cyanobacteria carryout oxygenic photosynthesis • Very similar mechanism to the eukaryotic process • Purple and green bacteria use anoxygenic photosynthesis • Bacteriochlorophyll pigments allow them to live in deeper, anaerobic zones of aquatic habitats

18. Cyanobacteria and Purple Bacteria

19. Deinococci and Nonproteobacteria Gram Negatives • Phylum Planctomycetes: • Lack peptidogylcan in their cell walls • Phylum Chlamydiae: • Nonmotile • Coccoid • Reproduce within the cytoplasmic vacuoles of their host cells • Energy parasites

20. Deinococci and Nonproteobacteria Gram Negatives • Phylum Spirochaetes: • Slender, long, helical bacteria • Motile due to axial filament • Phylum Bacteriodetes: • Obligate aerobes • Chemoheterotrophic • Nonsporing • Variable shapes

21. Proteobacteria • General characteristics: • Largest and most diverse group • Gram negative • Often called the purple bacteria • No obvious overall pattern of morphology or metabolism • Divided into 5 classes

22. Proteobacteria • Class Alphaproteobacteria: • Purple nonsulfur bacteria can grow anaerobically as photoorganoheterotrophs • Also aerobically as chemoorganoheterotrophs • Rickettsias are obligate intracellular parasites • Rhizobium carries out nitrogen fixation • Oxidize either ammonia or nitrite to nitrate

23. Proteobacteria • Class Betaproteobacteria: • Neisseria contains nonmotile, aerobic cocci that usually occur in pairs • Colonize mucous membranes • Buckholderia are aerobic rods • Almost always have a polar flagella • Some have sheaths • Some are chemolithotrophic

24. Proteobacteria • Class Gammaproteobacteria: • Largest subgroup • Some grow in long filaments or trichomes • Have gliding motility • Some use methane as their carbon source • Contains: • Pseudomonas – soil bacteria, pneumonia • Vibrionaceae – cholera, in raw shellfish • Enterobacteriaceae – human pathogen • Pasteurellaceae – domestic animal pathogens

25. Proteobacteria • Class Deltaproteobacteria: • Anaerobic • Can use sulfur as electron acceptots • Bdellovibrio is a bacteria parasite • Grows in their periplasmic space

26. Proteobacteria • Class Epsilonproteobacteria: • Smallest of the proteobacteria classes • Contain two important pathogenic genera: • Campylobacter • Helicobacter • Microaerophilic • Motile • Helical of vibroid

27. Low G and C Gram Positives • Phylum Firmicutes: • Class Clostridia • Class Mollicutes • Class Bacilli

28. Low G and C Gram Positives • Class Clostridia: • Anaerobic • Rods • Form endospores • Responsible for botulism, food spoilage, and putrefaction

29. Low G and C Gram Positives • Class Mollicutes: • Mycoplasmas are actually Gram negative • Grow on agar to resemble fried eggs • Smallest bacteria capable of self-reproduction • Lack cell walls • Why are they located in this section rather than with the other gram negative bacteria?

30. Low G and C Gram Positives • Class Bacilli: • Divided into 2 orders • Bacillales and Lactobacillales • Several important genera • Bacillus – food poisoning and anthrax • Thermoactinomyces – alergic reactions that lead to Farmer’s Lung • Lactobacillus – carries out lactic acid fermentation • Leuconostoc – used in cheese and buttermilk production

31. High G and C Gram Positives • General characteristics: • Form branching usually non-fragmenting hyphae • Asexual spores • Called conidiospores • Several distinctively different cell wall types • Phylum is Actinomycetes

32. High G and C Gram Positives • Suborder Actinomycineae: • Irregular in shape • Nonsporing • Rods • Cause disease in cattle an humans

33. High G and C Gram Positives • Suborder Corynebacterineae: • Mycobacterium form rods or filaments that readily fragment • Cell walls have a high lipid content and mycolic acids • Acid-fast • Contain several important human pathogens • Some form aerial mycelia with spores

34. High G and C Gram Positives • Suborder Propionibacterineae: • Common skin and intestinal inhabitants • Important in cheese making • Causative agents of acne vulgaris

35. High G and C Gram Positives • Suborder Streptomycineae: • Important decomposers of complex organic material • Produce useful antibiotics • Some are pathogenic to plants and animals

36. High G and C Gram Positives • Suborder Bifidobacteriales: • Irregular rod • Anaerobic • One of the first colonizers of the intestinal tract of babies

37. February 27th: Fungi • Widespread in the environment • Major limitation to growth are often water and temperature range • Secrete enzymes outside of their body and then absorb the digested food molecules • Eukaryotic, spore bearing, absorptive nutrition • No chlorophyll • Cell walls usually contain chitin

38. Importance • Important decomposers • All heterotrophic • Play a role in many industrial processes • Used as research tools

39. Structure • The body, or vegetative structure, of a fungus is called a thallus • Fungi are grouped into molds or yeasts based on the development of the thallus

40. Structure • Yeast: • Unicellular fungi that have a single nucleus • Asexual or budding reproduction • Sexual spore formation • Mold: • Consist of long branched filaments of cells, called hyphae, which form a tangled mass called a mycelium • Mycelium can produce reproductive structures

41. Structure • Some fungi alternate between mold and yeast forms in their lifecycle • This is called being dimorphic

42. Fungi Structure

43. Nutrition • Most are saprophytes • Grow best in moist dark habitats • Chemoorganoheterotrophic • Usually aerobic • Some yeasts are fermentive

44. Reproduction • Asexual reproduction often occurs in the fungi by production of spores that are easily dispersed • Sexual reproduction is initiated by the fusion of hyphae of different mating strains • In some fungi the nucleus of the two conjoined hyphae immediately fuse to form a zygote • In others the two nuclei stay separate, but divide synchronously, and may fuse later

45. Fungi Lifecycle

46. Fungal Divisions • Zygomycetes: • Coenocytic (multinucleate cells) • Saprophytic (decomposer) • Includes bread mold, Rhizopusstolonifer • Conjugation involves + and – strains • Basidiomycetes: • Called the club fungi

47. Fungal Divisions • Ascomycetes: • Called the sac fungi • Sac-shaped reproductive structure called an ascus • Deuteromycetes: • Also called ‘fungi imperfecta’ • They have no know sexual phase • Therefore imperfect

48. Slime Molds and Water Molds • The plasmodial (acellular) slime molds move about as a multinucleate plasmodium • When food or water is scarce, they form sporangia from which spores are produced

49. Slime Molds and Water Molds • The cellular slime molds consist of a vegetative stage called a myxamoeba • These feed until their nutrients are exhausted, then the cells come together to form a moldlike multicellular structure called a sorocarp • The sorocarp produces haploid cells that germinate when conditions are favorable

50. Slime Mold Pictures