MicrobiologyB.E Pruitt & Jane J. Stein

AN INTRODUCTIONEIGHTH EDITION

TORTORA • FUNKE • CASE

Chapter 11, part AThe Prokaryotes:

Domains Bacteria and Archaea

The Prokaryotes: Domains Bacteria and Archaea

• One circular chromosome, not in a membrane• No histones• No membrane bounded organelles (ribosomes)• Peptidoglycan cell walls (NOT in Archaea)• Binary fission

The Prokaryotes

• Gram-negative groups:• Proteobacteria

• Mythical Greek god, Proteus, who could assume many shapes

• By RNA sequencing• Proteobacteria:

• Human pathogens• Brucella• Bartonella

• Obligate intracellular• Rickettsia• Ehrlichia

• Have prosthacae• Caulobacter

• Chemoautotrophic• Nitrobacter• Nitrosomas

• Fix nitrogen• Rhizobium• Azospirillum

• Produce acetic acid• Acetobacter

Domain Bacteria: Proteobacteria

• (alpha) Proteobacteria • Human pathogens:

• Bartonella• B. hensela Cat-scratch disease

• Brucella Brucellosis

The (alpha) Proteobacteria

http://www.cdc.gov/ncidod/dbmd/diseaseinfo/brucellosis_g.htm#top

The alpha-proteobacteria include nitrogen-fixing bacteria, chemoautotrophs, and chemoheterotrophs. Some members of this sub-phylum grow at low-nutrient levels (oligotrophic) and some have stalks (prosthecae). Some are pathogens and some are intracellular.

• Obligate intracellular parasites:• Rickettsia. Arthropod-borne, spotted fevers

• R. prowazekii Epidemic typhus - lice• R. typhi Endemic murine typhus - flea• R. rickettsii Rocky Mountain Spotted Fever -

tick

The (alpha) Proteobacteria

The (alpha) Proteobacteria

Figure 11.1

• Those with prosthecae:• Caulobacter. Stalked

bacteria found in lakes. Use stalk for obtaining nutrients

• Hyphomicrobium. Budding bacteria found in lakes

The (alpha) Proteobacteria

Figure 11.2 & 3

Insert Fig 11.2b

Figure 11.2b Caulobacter.

• A plant pathogen:• Agrobacterium.

Insert a plasmid into plant cells, inducing a tumor

The (alpha) Proteobacteria

Figure 9.17

• Nitrogen Cycle• Chemoautotrophic:

• Oxidize nitrogen for energy• Fix CO2

• Nitrosomonas NH3+ NO2

– (now β betaproteobacteria)

• Nitrobacter NO2– NO3

–

The (alpha) Proteobacteria

• Nitrogen-fixing bacteria:• Azospirillum

• Grow in soil, using nutrients excreted by plants

• Fix nitrogen• Rhizobium

• Fix nitrogen in the roots of plants

The (alpha) Proteobacteria

Figure 27.5

Figure 27.5 The formation of a root nodule.

An infection thread isformed, through whichbacteria enter root cells.

Enlarged root cellsform a nodule.

Bacteria change into bacteroids; packed root cells enlarge.

Rhizobia attachto root hair.

Pea plant

Roothairs

Rhizobia

Infectionthread

Bacteroids

Root

Nodules

• Produce acetic acid from ethyl alcohol:• Acetobacter - Pasteur

The (alpha) Proteobacteria

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