Overview of Gram-Positive and Other Bacteria

1. © 2012 Pearson Education, Inc. Overview of Gram-Positive and Other Bacteria • Bacteria has many phyla other than Proteobacteria, including • Gram-positive bacteria • Large group of mostly chemoorganotrophs • Cyanobacteria • Oxygenic phototrophs that have evolutionary roots near those of gram-positive bacteria • Phylogenetically early-branching phyla • Such as Aquifex • Other morphologically distinct groups

2. © 2012 Pearson Education, Inc. I. Firmicutes, Mollicutes, and Actinobacteria • Gram-positive bacteria are a large and diverse group • Divided into three groups: • Firmicutes • Mollicutes • Actinobacteria

3. © 2012 Pearson Education, Inc. 18.1 Nonsporulating Firmicutes • Key genera: Staphylococcus, Streptococcus, Lactobacillus, Sarcina • Staphylococcus andMicrococcus (Figure 18.1) • Aerobic, cocci • Resistant to reduced water potential • Tolerate high salt • Many species are pigmented • Staphylococcus aureus

4. Figure 18.1 © 2012 Pearson Education, Inc.

5. © 2012 Pearson Education, Inc. 18.1 Nonsporulating Firmicutes • Streptococcus • Play important roles in production of buttermilk, silage, and other products • Some species are pathogenic • Lactococcus: genera of dairy significance (Figure 18.3) • Enterococcus: genera of fecal origin

6. Figure 18.3 © 2012 Pearson Education, Inc.

7. © 2012 Pearson Education, Inc. 18.2 Endospore-Forming Firmicutes • Key genera: Bacillus & Clostridium • Distinguished on the basis of cell morphology, and the shape and cellular position of endospore • Generally found in soils • Endospores are advantageous for soil microorganisms

8. Figure 18.5 © 2012 Pearson Education, Inc.

9. © 2012 Pearson Education, Inc. 18.2 Endospore-Forming Firmicutes • Bacillus • Many produce extracellular hydrolytic enzymes that break down polymers • Many bacilli produce antibiotics • Bacillus thuringiensis produces insect larvicides (Figure 18.6)

10. Endospore Crystal Figure 18.6 © 2012 Pearson Education, Inc.

11. © 2012 Pearson Education, Inc. 18.2 Endospore-Forming Firmicutes • Clostridium • Lack a respiratory chain, anaerobic • Mainly found in anaerobic pockets in the soil • Also live in mammalian intestinal tract • Some cause diseases such as botulism, tetanus, and gangrene

12. © 2012 Pearson Education, Inc. 18.3 Mollicutes: The Mycoplasmas • Key genera: Mycoplasma • Lack cell walls • Some of the smallest organisms capable of autonomous growth • Parasites that inhabit animal and plant hosts • Key components of peptidoglycan are missing • Mycoplasma cells are pleomorphic • Cells may be cocci or filaments of various lengths

13. Figure 18.9 © 2012 Pearson Education, Inc.

14. © 2012 Pearson Education, Inc. 18.4 Actinobacteria: Coryneform & Mycobacteria • Key genera: Corynebacterium & Mycobacterium • Actinobacteria form their own phylum • Over 30 taxonomic families • Rod-shaped to filamentous, usually aerobic • Mostly harmless commensals (Mycobacterium are exceptions) • Valuable for antibiotics and certain fermented dairy products

15. © 2012 Pearson Education, Inc. 18.4 Actinobacteria: Coryneform & Propionic Acid Bacteria • Corynebacterium • Gram-positive, aerobic, nonmotile, rod-shaped • Form club-shaped, irregular-shaped, or V-shaped cell arrangements • Extremely diverse

16. Figure 18.12 © 2012 Pearson Education, Inc.

17. © 2012 Pearson Education, Inc. 18.5 Actinobacteria: Mycobacterium • Mycobacterium • Rod-shaped organisms, exhibit acid-fastness (Figure 18.15) • First discovered by Robert Koch • Not readily stained by Gram stain because of high surface lipid content

18. Figure 18.16 © 2012 Pearson Education, Inc.

19. © 2012 Pearson Education, Inc. 18.6 Filamentous Actinobacteria: Streptomyces & Relatives • Key genera: Streptomyces, Actinomyces (Figure 18.18) • Filamentous, gram-positive bacteria • Produce mycelium analogous to mycelium of fungi • Over 500 species of Streptomyces • Streptomyces spores are called conidia (Figure 18.19) • Primarily soil microorganisms, responsible for earthy odor of soil (geosmins) • Strict aerobes that produce many extracellular enzymes

20. Figure 18.18 © 2012 Pearson Education, Inc.

21. © 2012 Pearson Education, Inc. 18.6 Filamentous Actinobacteria: Streptomyces & Relatives • Streptomyces (Figure 18.22) • 50% of all isolated Streptomyces produce antibiotics (Figure 18.23) • Over 500 distinct antibiotics produced by Streptomyces • Some produce more than one antibiotic • Genomes are typically quite large (8 Mbp and larger) • Knowledge of the ecology of Streptomyces remains poor

22. Figure 18.22 © 2012 Pearson Education, Inc.

23. Figure 18.23 © 2012 Pearson Education, Inc.

24. © 2012 Pearson Education, Inc. 18.7 Cyanobacteria • Phototrophic • Gas vesicles are found in many cyanobacteria • Help maintain buoyancy • Keep cell in water column where there is light • Heterocysts are rounded, enlarged cells • Anoxic environment inside heterocyst • Site for nitrogen fixation • Nitrogenase is sensitive to oxygen

25. Figure 18.24 © 2012 Pearson Education, Inc.

26. Heterocyst Figure 18.26 Glutamine Heterocyst Vegetative cells Vegetative cells © 2012 Pearson Education, Inc.

27. © 2012 Pearson Education, Inc. 18.9 The Chlamydia • Key genera: Chlamydia • Obligately parasitic with poor metabolic capacities • Some of the simplest biochemical capacities of all known bacteria • Currently one of the leading sexually transmitted diseases

28. Figure 18.30 © 2012 Pearson Education, Inc.

29. Release ofelementary bodies Elementary bodies Conversion toelementary bodies Figure 18.31 Elementary body Elementary bodyattacks host cell Reticulate body Multiplicationof reticulatebodies Phagocytosis ofelementary body Conversion toreticulate body © 2012 Pearson Education, Inc.

30. © 2012 Pearson Education, Inc. 18.10 Planctomyces: A Phylogenetically Unique Bacterium • Key genera: Planctomyces • Planctomyces is a budding bacterium • Facultative aerobic chemoorganotroph • Stalked • Primarily aquatic • Extensive cell compartmentalization including a membrane-enclosed nuclear structure

31. Flagellum Figure 18.32 Pilus Stalk Stalk © 2012 Pearson Education, Inc.

32. Nucleoid Figure 18.33 Nuclearenvelope © 2012 Pearson Education, Inc.

33. © 2012 Pearson Education, Inc. Bacteroides • Key genera: • Bacteroides • Obligately anaerobic • Numerically dominant bacterium in human intestinal tract

34. © 2012 Pearson Education, Inc. 18.15 Chlorobium andOther Green Sulfur Bacteria • Key genera: Chlorobium • Phylogenetically distinct, nonmotile, anoxygenic phototrophs • Utilize H2S as an electron donor and oxidize it to SO42 • Have chlorosomes bacteriochlorophyll-rich bodies bounded by a thin membrane • Green- and brown-colored species exist

35. Figure 18.39 © 2012 Pearson Education, Inc.

36. © 2012 Pearson Education, Inc. 18.15 Chlorobium andOther Green Sulfur Bacteria • Green sulfur bacteria inhabit anoxic environments rich in H2S • Some green sulfur bacteria form consortia • Involves the green sulfur bacterium and a chemoorganotrophic bacterium

37. © 2012 Pearson Education, Inc. 18.16 Spirochetes • Key genera: Spirochaeta, Treponema, Leptospira, Borrelia • Gram-negative, motile, and coiled • Widespread in aquatic environments and in animals • Have endoflagella: located in the periplasm of the cell • Also found in the rumen of animals

38. Figure 18.42 © 2012 Pearson Education, Inc.

39. Endoflagellum (rigid,rotates, attached to oneend of protoplasmiccylinder) Outer sheath(flexible) Figure 18.43 Endoflagellum Protoplasmiccylinder Outersheath Protoplasmic cylinder(rigid, generally helical) © 2012 Pearson Education, Inc.

40. © 2012 Pearson Education, Inc. 18.16 Spirochetes • Spirochaeta • Free-living, anaerobic and facultatively anaerobic spirochetes • Treponema (Figure 18.45a) • Anaerobic host-associated spirochetes that are commensal or parasites of humans • Borrelia (Figure 18.45b) • Majority are human or animal pathogens • Borrelia burgdorferi is the causative agent of Lyme disease • B. burgdorferi has a linear chromosome

41. © 2012 Pearson Education, Inc. Deinococcus • Deinococcus • Gram-positive, aerobic, organotrophic • Most are red or pink due to carotenoids • Resist UV radiation, gamma radiation, and desiccation • Resistant to most mutagenic agents

42. © 2012 Pearson Education, Inc. 18.20 Aquifex • Key genera: Aquifex • Aquifex • Obligately chemolithotrophic hyperthermophile • Most thermophilic of all Bacteria (can grow at 95C) • 1.55-Mbp genome