1. Bacteria: The Deinococci and Nonproteobacteria Gram Negatives
Chapter 21
Bacteria: The Deinococci and Nonproteobacteria Gram Negatives

2. Life on Earth evolved along three major lines, called domains, all derived from a common ancestor. Each domain contains several phyla. The domains, Bacteria and Archaea, remained prokaryotic, whereas the third, Eukarya, evolved into the modern eukaryotic cell.

3. Aquificae and Thermotogae
Thermophiles that grow at temperatures above 85° C -Aquificae and Thermotogae
Figure 21.1

5. Phylum Aquificae Thought to be deepest (oldest) branch of Bacteria
Contains one class, one order, and five genera
two best studied genera are Aquifex and Hydrogenobacter

6. Genus Aquifex
Thermophile with a growth optimum of 85°C and a maximum of 95°C
Microaerophilic
Chemolithoautotroph
-uses hydrogen, thiosulfite, and sulfur as electron donor
-uses oxygen as electron acceptor
-genome ~1/3 size of E. coli

7. Phylum Thermotogae Second deepest branch of Bacteria
Contains one class, one order, and six genera
best studied genus is Thermotoga

8. Genus Thermotoga Gram-negative rods Thermophiles
have outer sheathlike envelope that can balloon out from ends of cell
Thermophiles
optimum 80°C; maximum 90°C
grow in active geothermal areas
terrestrial solfataric springs

9. Thermotoga… Chemoheterotrophs e.g., Thermatoga maritima
have functional glycolytic pathway
can grow anaerobically on carbohydrates and proteins digests
e.g., Thermatoga maritima
~24% of coding sequences are similar to archaeal genes

10. Figure 21.2

11. Deinococcus-Thermus

12. Genus Deinococcus Deinococcus is best studied Spherical or rod-shaped
associated in pairs or tetrads
stain gram-positive but do not have typical gram-positive cell wall
layered outer membrane similar to gram-negatives
L-ornithine in peptidoglycan
lacks teichoic acid

13. Figure 21.3

15. Deinococcus… Mesophilic Mesophilc, aerobic, produce acid
Extraordinarily resistant to desiccation and radiation
can survive 3-5 million rad (100 rad lethal to humans)
Isolated from ground meat, feces, air, fresh water, and other sources, but natural habitat unknown

16. Deinococcus……
Genome consists of two circular chromosomes, a megaplasmid, and a small plasmid
radiation resistance due to ability to repair genome when it is severely damaged
Rapidly repairs fragmented DNA within hours when exposed to radiation
D. radiodurans shown to have an efficient DNA repair system

17. Photosynthetic Bacteria
Three groups of photosynthetic bacteria
the purple bacteria
the green bacteria
the cyanobacteria
differ from the purple and green bacteria by carrying out oxygenic photosynthesis
have two photosystems
use water as an electron donor and generate oxygen during photosynthesis

18. Bloom of Purple Sulfur Bacteria, Sulfide Spring, Madison, WI
Alga
Bloom of Purple Sulfur Bacteria, Sulfide Spring, Madison, WI

20. differences in absorption spectra correlates with ecological
distribution
absorption spectra of 5 photosynthetic bacteria showing the differences in absorption maxima and the contributions of various accessory pigments
Figure 21.4

22. Taxonomy of Photosynthetic Bacteria
Phylum Chloroflexi – green nonsulfur bacteria
Phylum Chlorobi – green sulfur bacteria
Phylum Cyanobacteria
Phylum proteobacteria purple bacteria
purple sulfur bacteria
purple non-sufur bacteria
phylum Firmicutes – heliobacteria
There appears to have been considerable horizontal transfer of photosynthetic genes between the 5 phyla. About 50 genes related to photosynthesis are common to all 5 phyla.

23. Purple sulfur bacteria: Note the sulfur granules deposited inside the cells
Green sulfur bacteria: Note the sulfur granules deposited outside the cells

24. Halophilic Purple bacteria Chlorosomes from green bacteria
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Purple bacteria
Halophilic Purple bacteria
Chlorosomes from green bacteria

25. Phylum Chlorobi Green sulfur bacteria Morphologically diverse
rods, cocci, or vibrios; single cells, chains, or clusters

26. Chlorobi… Have chlorosomes
ellipsoidal vesicles attached to plasma membrane
contain accessory photosynthetic pigments
most efficient light harvesting complexes found in nature

27. Chlorosomes –Green Sulfur & Green Non-sulfur

28. Chlorobi… Lack flagella; nonmotile Some have gas vesicles
used to adjust depth of cell for adequate light and H2S
Obligately anaerobic photolithoautotrophs
use H2S, elemental sulfur and H2 as electron sources
elemental sulfur deposited outside cell

29. Figure 21.5

30. Phylum Chloroflexi Green nonsulfur bacteria
Contains photosynthetic and nonphotosynthetic members
e.g., genus Chloroflexus – photosynthetic
e.g., genus Herpetosiphon - nonphotosynthetic

31. Genus Chloroflexus Thermophilic Metabolism
often isolated form neutral to alkaline hot springs
grow in form of orange-reddish mats
Metabolism
anoxygenic photosynthesis
does not use water as electron donor
photoheterotroph
can grow aerobically as a chemoheterotroph

32. Chloronema sp. on stratified Michigan Lake
Chloroflexus sp.

33. Phylum Cyanobacteria
Largest, most diverse group of photosynthetic bacteria
Most obligate photolithoautotrophs; some can grow slowly in dark as chemoheterotrophs
One current classification system divides group into 62 species and 24 genera

34. Photosynthesis in cyanobacteria
Resembles that of eucaryotes
have chlorophyll a
prochlorophytes have chlorophyll a and b
have photosystem I and II
oxygenic photosynthesis

35. Photosynthesis in cyanobacteria…
Use phycobiliproteins as accessory pigments
phycobilisomes, which line thylakoid membranes, contain phycocyanin and phycoerythrin
prochlorophytes lack phycobilins
use Calvin cycle to fix CO2

36. Cyanobacterial Thylakoids and Phycobilisomes
Figure 21.6

37. typical gram- negative contains cell phyco- wall bilin pigments site
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typical
gram-
negative
cell
wall
contains
phyco-
bilin
pigments
site of
photo-
synthesis
nitrogen
storage
polymer
Schematic drawing of a vegetative cyanobacterial cell. The insert shows an enlarged view of the envelope with its outer membrane and peptidoglycan.
Figure
21.7 (a)

38. Thin section of Synechocystis during division
Thin section of Synechocystis during division. Thylakoid membranes house photosynthetic pigments and ETC components. Phycobilisomes line the thylakoid membranes and contain phycobilin pigments, especially phycocyanin. Carboxysomes contain ribulose 1,5-bisphosphate carboxylase, which is an important enzyme of the Calvin Cycle.
Figure 21.7b

39. Oxygenic Photosynthetic Bacteria
Figure 21.8

40. Heterocysts Specialized cells used for nitrogen fixation
produced when organism is nitrogen deprived
differentiate from individual cells in filament
involves reorganization of photosynthetic membranes
thick heterocyst wall prevents O2 diffusion into heterocyst which would inactivate nitrogenase, enzyme responsible for nitrogen fixation

41. Heterocysts and Akinetes
Figure 21.9

42. Prochlorophytes
Cyanobacteria in genera Prochloron, Prochlorococcus, and Prochlorothrix
distinguished by presence of chlorophyll a and b and lack of phycobilins
are the only procaryotes to possess chlorophyll b
makes them candidates as ancestors of endosymbionts that give rise to chloroplasts

43. Prochloron
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Figure 21.10

44. Ecology of cyanobacteria
Tolerant of environmental extremes
thermophilic species can grow at temperatures up to 75°C
often are primary colonizers
Can cause blooms in nutrient-rich ponds and lakes
some produce toxins
Often form symbiotic relationships
e.g., are phototrophic partner in most lichens
e.g., symbionts with protozoa and fungi
e.g., nitrogen-fixing species form associations with plants

45. Copyright © The McGraw-Hill Companies, Inc
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Figure 21.11

46. Phylum Chlamydiae

47. Genus Chlamydia Gram-negative bacteria
cell walls lack muramic acid and peptidoglycan
have very small genomes
Obligate intracellular parasites with unique developmental cycle
involving formation of elementary body (EB) and reticulate body (RB) or initial body
found mostly in mammals and birds
some recently isolated from spiders, clams, and freshwater invertebrates

48. Figure 21.13b

49. Chlamydial metabolism
Appear to be energy parasites, obtaining ATP from host
do have genes for substrate-level phosphorylation, electron transport, and oxidative phosphorylation
Reticulate bodies have biosynthetic capabilities when supplied precursors from host; can synthesize some amino acids
Elementary bodies seem to be dormant forms

50. Important pathogens C. trachomatis C. psittaci C. pneumoniae
infects humans and mice
causes trachoma, nongonococcal urethritis, and other diseases in humans
C. psittaci
infects humans and many other animals
causes psittacosis in humans
C. pneumoniae
common cause of human pneumonia

51. Phylum Spirochaetes
Gram-negative bacteria with distinctive structure and motility
slender, long with flexible helical shape
creeping (crawling) motility due to a structure called an axial filament
Chemoheterotrophs
Ecologically diverse

52. Figure 21.14

53. axial filament = complex of axial fibrils (periplasmic flagella)
Figure (a1) and (a2)

54. Figure (b)

55. Figure (c) and (d)

56. Spirochete Motility current thought: axial fibrils rotate, causing
corkscrew-shaped outer sheath
to rotate and move cell through
surrounding liquid
Figure 21.16

57. Symbiotic Associations
Broad range of organisms
Found in a variety of locations, for example
hindguts of termites
digestive tracts of mollusks and mammals
oral cavities of animals

58. Spirochete-Protozoan Associations
Figure 21.17