The Prokaryotes:
BacteriaFebruary 4, 2015
The Prokaryotes
Domain Bacteria
Proteobacteria
Gram-negative
Chemoheterotrophic
Divided into 5 groups
Alphaproteobacteria
Betaproteobacteria
Gammaproteobacteria
Deltaproteobacteria
Epsilonproteobacteria
The Alphaproteobacteria
Capable of growth in nutrient-deprived environments
Some contain prosthecae. Stalk like buds function to anchor the bacteria and absorb nutrients
Pelagibacter ubique
20% of prokaryotes in oceans
Constitutes 0.5% of all prokaryotes
1354 genes (relatively small genome)
Symbiotic bacteria that have lower metabolic requirements have the smallest genomes
Insert Fig 11.2b
Figure 11.2b Caulobacter.
May grow in laboratory water baths
The Alphaproteobacteria
Human pathogens (zoonosis) Bartonella:
B. henselae: cat-scratch disease. Infects RBCs.
Brucella:
B. melitensis: brucellosis. Survives in phagocytes
Obligate intracellular parasites Rickettsia: arthropod-borne, spotted fevers
R. prowazekii: epidemic typhus. Transmitted by lice.
R. typhi: endemic murine (mice) typhus
R. rickettsii: Rocky Mountain spotted fever. Damage blood capillaries
Ehrlichia: live obligately in white blood cells
Tickborne (Lone star tick)
Causes ehrlichiosis which can be fatal
Figure 11.1 Rickettsias.
Slime layerScattered rickettsias
Chicken embryo cell
Nucleus
Masses of rickettsias in nucleus
A rickettsial cell that has just been released from a host cell
Rickettsias grow only within a host cell, such as the chicken embryo cell shown here. Note the scattered rickettsias within the cell and the compact masses of rickettsias in the cell nucleus.
The Alphaproteobacteria
Wolbachia: live in insects and other animals
Only live inside of cells of their hosts (insects)
Difficult to culture
75% of all species of animals carry this bacteria
May lyse the cells of the infected host or cause the infected host to not reproduce
Applications of Microbiology 11.1b In an infected pair, only female hosts can reproduce.
Neither infectedUninfected offspring
Male infectedNo offspring
Female infectedInfected offspring
Both infected Infected offspring
Unfertilized female infectedInfected female offspring
Wolbachia
Females
Males
The Alphaproteobacteria
Plant pathogen
Agrobacterium: insert a plasmid into plant cells, inducing a tumor (crown gall)
Figure 9.19 Crown gall disease on a rose plant.
Crown gall
The Alphaproteobacteria
There are some industrial important alphaproteobacteria
Acetobacter
Gluconobacter
Both produce acetic acid (vinegar) from ethanol
The Betaproteobacteria
Often uses nutrient substances that diffuse away from areas of anaerobic decomposition of organic matter
Hydrogen gas
Ammonia
Methane
The Betaproteobacteria
Burkholderia
Motile (single flagella), aerobic, gram-negative rod
Capable of degrading 100 different organic molecules
Confers the ability to contaminate drugs in hospitals
Nosocomial infections (cystic fibrosis)
Bordetella
Chemoheterotrophic; rods
B. pertussis
Non-motile, aerobic gram-negative rods
Causative agent of pertussis (whooping cough)
Neisseria
Aerobic gram-negative cocci
Inhabits mucous membranes of mammals
Causative agents of gonorrhea and meningococcal meningitis
Figure 24.7 Ciliated cells of the respiratory system infected with Bordetella pertussis.
B. pertussis
Cilia
The Gammaproteobacteria
Constitute the largest subgroup of Proteobacteria
Order Pseudomonadales Gram-negative rods or cocci
Genus Pseudomonas (rods)
Common in soil
Opportunistic pathogens (urinary tract, burns, wounds….may cause sepsis and meningitis)
Capable of growth in antiseptics. High resistance to antibiotics (encodes for efflux pumps)
Excrete water soluble pigments into media (blue-green pigmentation with UV light)
The Gammaproteobacteria
Pseudomonadales
Genus Moraxella
Aerobic coccobacilli (between coccus and rod)
Conjunctivitis : inflammation of the conjunctiva
The Gammaproteobacteria
Legionellales
Legionella
Found in streams, warm-water pipes, cooling towers
Can survive and reproduce within aquatic amoebas
Difficult to eradicate in water systems
L. pneumophilia causes legionellosis (pneumonia)
Coxiella
Obligate intracellular pathogen
Causative agent of Q fever
Transmitted via aerosols or unpasteurized milk
The Gammaproteobacteria
Vibrionales
Facultative anaerobic gram-negative rods
Found in coastal water
Vibrio cholerae causes cholera
Profuse and watery diarrhea (dehydration)
V. parahaemolyticus causes gastroenteritis (inflammation of intestines)
May be transmitted to humans via undercooked shellfish
Vibrio vulnificus causes cellulitis or septicemia
Figure 11.8 Vibrio cholerae.
The Gammaproteobacteria Enterobacteriales (enterics)
Peritrichous flagella; facultatively anaerobic
Active fermenters of glucose and other carbs
Fimbriae helps bacteria attach to membranes
Sex pili aid in DNA transfer
Enterobacter Erwinia Escherichia Klebsiella Proteus Salmonella Serratia Shigella Yersinia
The Gammaproteobacteria
Order Pasteurellales
Haemophilus
Inhabit mucous membranes of upper respiratory tract, mouth, vagina, and GI tract
Requires X (heme) and V (NAD+, NADP+) factors
Laboratory tests for X and V factors help identify organism
Causes meningitis/earaches in children. Epiglotitis, bronchitis, and pneumonia
The Deltaproteobacteria
Includes bacteria that are predators of other bacteria
Bdellovibrio
Attacks other gram-negative bacteria
Reproduces in the periplasm of the infecting host
How can Deltaproteobacteria be beneficial?
The Epsilonproteobacteria
Gram-negative helical or curved rods
Campylobacter
Microaerophile
One polar flagellum
Leading cause of food-borne gastroenteritis
Helicobacter
Multiple flagella
Most common cause of peptic ulcers in humans
Infection has been associated with the development of stomach cancer
50% of all humans are colonized with H. pylori