Phylogeny of bacteria
Nonproteobacteria gram-negative bacteria
Many gram-negative bacteria
belong to diverse phyla which
differ from the proteobacteria
Some belong to the oldest
branches of bacteria while others
have arisen more recently
Aquificae and Thermotogae
The two oldest branches of
bacteria
Both are hyperthermophilic
Deinococcus-Thermus
Species belonging to the genus
Deinococcus are best studied
Very resistant to radiation and
desiccation
T. aquaticus  Taq polymerase
Deinococcus
Often associate in pairs
and tetrads
Stain gram + although
cell wall is similar to
gram cells
Photosynthetic nonproteobacteria
Photosynthetic nonproteobacteria
Phylum Chloroflexi
Also contains nonphotosynthetic bacteria
Are the green nonsulfur bacteria
Can be isolated from neutral to alkaline hot springs
Photosynthetic nonproteobacteria
Phylum Chlorobi
Composed of 1 class, 1 order and 1 family
Are the green sulfur bacteria
Use sulfur and sulfur-containing compounds as electron
sources
Photosynthetic nonproteobacteria
Phylum Cyanobacteria
Largest and most diverse group of photosynthetic bacteria
Photosynthetic system resembles that of eukaryotes
Employ a variety of reproductive mechanisms
(e.g. binary fission, multiple fission, budding and
fragmentation)
Photosynthetic nonproteobacteria
Phylum Cyanobacteria
Vary greatly in shape and appearance
Phylum Planctomycetes
Spherical or oval bacteria that lack
peptidoglycan
Reproduce by budding
In some species the nuclear body is
membrane-bound
Phylum Chlamydiae
Originally grouped with the
rickettsias (rickettsias now in
-proteobacteria)
Both are small obligate
intracellular parasites
Genus Chlamydia is the best
studied
Phylum Chlamydiae
Three species are important human
pathogens
Cell walls lack peptidoglycan
Osmotic stability achieved by
cross-linking of outer membrane
proteins with disulfide bonds
Chlamydial life cycle
Phylum Spirochaetes
Distinguished by their structure and mechanism of motility
Slender long bacteria with a helical shape
Many are too thin to be seen using phase-contrast or dark-field
microscopy
Phylum Spirochaetes
Phylum Spirochaetes
Ecologically diverse
Some are free-living (soil and freshwater)
Others live in symbiotic relationships with other organisms
(insects, mollusks and mammals)
Phylum Spirochaetes
Phylum Spirochaetes
Some species are human pathogens
e.g.
Treponema pallidum (Syphilis)
Borrelia burgdorferi (Lyme disease)
Phylum Spirochaetes
Cells are bound by flagella
called endoflagella (or axial
fimbrils or periplasmic flagella)
Complex of flagella called axial
filaments
Filaments bound by a sheath
Phylum Spirochaetes
Motility likely due to rotation
of filaments
Rotation causes corkscrew-like
movement of the cell
Phylum Bacteroidetes
Very diverse phylum
Closely related to Chlorobi
Anaerobic rods of various shapes
Phylum Bacteroidetes
Phylum Bacteroidetes
Grow in the oral cavities and intestinal tracts of animals
They are often beneficial to their host
B. fragilis is the cause of anaerobic infections in humans