Chapter 11: Characterizing and Classifying Prokaryotes

General Characteristics of Prokaryotic Cells

¡Morphology of Prokaryotic Cells- Three basic shapes (with variations) of prokaryotes:

-cocci-

-coccobaccilus

-bacilli-

-vibrio

-spiral-

-spirilla

-spirochetes

-pleomorphic-

¡Endospores

-Bacillus and Clostridium, Gram (+) cells, form endospores.

-endospores are not reproductive structures, but a defensive strategy against hostile or unfavorable conditions.

-a vegetative cell creates an endospore when one or more nutrients are in limited supply.

-endospores are extremely resistant to drying, heat, radiation, and lethal chemicals.

¡Reproduction of Prokaryotic Cells- All prokaryotes reproduce asexually

-binary fission-

-snapping division-

-spores-

-budding-

¡Arrangements of Prokaryotes Cells

-diplococci-

-streptococci-

-tetrad-

-sarcinae-

-staphylococci-

-diplobacillus-

-streptobacillus-

-V-shape-

-palisade-.

Modern Prokaryotic Classification

¡Initial classification is currently based on nucleotide sequence in DNA and RNA and amino acid sequence in proteins.

¡Nucleotide sequence in rRNA is the primary point of division

Survey of Archaea

¡Besides differences of rRNA, the archaea are distinguished from bacteria by

¡There are two phyla of archaea: crenarchaeota and euryarchaeota

¡can be various shapes, cell walls made of a variety of compounds, but no peptidoglycan.

¡no archaea are known to cause diseases to humans or animals.

¡Extremophiles- microbes that require extreme conditions of temperature, pH, an/or salinity to survive

-Thermophiles-

-Hyperthermophiles-

-Halophiles-

-Methanogens-

¡Most archaea live in moderate environments

Survey of Bacteria

¡Deeply Branching and Phototrophic Bacteria

-Deeply branching bacteria are thought to be the closest relatives to the earliest life forms, having characteristics that allow them to live in environments similar to what scientists think early Earth would have been like.

-Phototrophic bacteria acquire energy from light, and most are autotrophic.

-Cyanobacteria-

-Green and Purple Phototrophic Bacteria-

¡Gram Positive Bacteria (see table 11.2) focus on:

Low G+C Gram (+) Bacteria

-Clostridia (tetanus, botulism, gangrene, severe diarrhea)

-Bacillus (anthrax)

-Streptococcus (strep throat, scarlet fever)

-Staphylococcus (bacteremia, food poisoning)

High G+C Gram (+) Bacteria

-Corynebacterium (diphtheria)

-Mycobacterium (tuberculosis, meningitis, leprosy)

-Streptomyces (rare sinus infections, produces antibiotics)

¡Gram-Negative Bacteria (see tables 11.3 and 11.4) focus on:

Alphaproteobacteria

-Rhizobium (nitrogen fixers)

Betaproteobacteria

-Neisseria (gonorrhea, meningitis)

Gammaproteobacteria

-Legionella (Legionnaires’ disease)

-Yersinia (plague)

-Klebsiella (pneumonia)

Epsilonproteobacteria

-Helicobacter (gastric ulcers)

-Campylobacter (gastroenteritis)

Spirochetes

-Treponema (syphilis)

-Borellia (Lyme disease)