CHARACTERIZING AND CLASSIFYING PROKARYOTES

CHAPTER 11

Prokaryotes

Most diverse group of organismsHabitats

All possible habitats are exploited by some sort of prokaryote

Only a few capable of colonizing humans and causing disease

Morphology of Prokaryotic Cells

Figure 11.1

Arrangements of Prokaryotic Cells

Result from two aspects of division during binary fission Planes in which cells divide Separation of daughter cells

Arrangements of Cocci: Diplococci

Figure 11.6a

Arrangements of Cocci: Streptococci

Figure 11.6b

Arrangements of Cocci: Tetrads

Figure 11.6c

Arrangements of Cocci: Staphylococci

Figure 11.6e

Arrangements of Bacilli: Single Bacillus

Figure 11.7a

Arrangements of Bacilli: Diplobacilli

Figure 11.7b

Arrangements of Bacilli: Streptobacilli

Figure 11.7c

Arrangements of Bacilli: V-Shape and Palisade

Figure 11.7d

Endospores

Produced by Gram-positive bacteria Bacillus and Clostridium are examples

Each vegetative cell transforms into one endosporeEach endospore germinates to form one vegetative

cellConstitute a defensive strategy against hostile or

unfavorable conditionsEndospores are not reproductive structures

Modern Prokaryotic Classification

Three domains of Life Archaea (prokaryote) Bacteria (prokaryote) Eukarya (eukaryote)

Archaea

Features of Archaea

Prokaryotes (no membrane bound nucleus) Lack Peptidoglycan in their cell walls Genome is circular DNA Histone proteins are present Ribosomes are more similar to bacteria than

eukaryotes Many occupy "extreme' environments.

Extremophiles Not known to cause disease in humans or animals

Halophiles

Inhabit extremely saline habitatsDepend on greater than 9% NaCl to maintain integrity

of cell wallsMany contain red or orange pigments; protection from

visible and UV lightExtreme Halophiles… require very high salt (not just

tolerant) Most require at least 9 % NaCl Most require 12-23% NaCl for optimal growth Almost all can grow at 32% NaCl

Most studied – Halobacterium salinarium

Extreme Halophiles

Great salt lake

Seawater evaporation

ponds

SEM of halophiles

African “soda lake” high

alkalinity, high salinity

Methanogens

Convert carbon dioxide, hydrogen gas, and organic acids to methane gas

Largest group of archaeaConvert organic wastes in pond, lake, and ocean

sediments to methaneSome live in colons of animals; are one of primary

sources of environmental methane

Methanogens

CH4 (methane producers)Strict anaerobesExample genus: Methanococcus

Methanogens

Methanogen habitats

Hyperthermophiles

Most are obligate anaerobesMost require S as part of their metabolic schemeExample Genera:

Sulfolobus Thermococcus Pyrolobus

Hyperthermophiles – require temperatures over 80ºCHeat stable biomolecules

Hyperthermophile Habitats

Bacterial groups

Phototrophic Bacteria

PhotoautotrophsFive groups … (often grouped by color)

Blue-green bacteria (cyanobacteria) Chlorophyll a (oxygenic photosynthesis)

Green sulfur bacteria bacteriochlorophyll Green nonsulfur bacteria “ Purple sulfur bacteria “ Purple nonsulfur bacteria “

Phototrophic Bacteria

Table 11.1

Low G + C Gram-Positive Bacteria

ClostridiaMycoplasmaBacillusListeriaLactobacillus Streptococcus Staphylococcus

High G + C Gram-Positive Bacteria

Includes rod-shaped cells and filamentous bacteriaCorynebacteriumMycobacteriumActinomycetes

Actinomyces Nocardia Streptomyces

Actinomycetes

Figure 11.17

Gram-Negative Proteobacteria

Largest and most diverse group of bacteria More diseases are caused by this group than any other.

Five distinct classes Alphaproteobacteria Betaproteobacteria Gammaproteobacteria Deltaproteobacteria Epsilonproteobacteria

Alphaproteobacteria

Nitrogen fixers Azospirillum Rhizobium

Nitrifying bacteria Nitrobacter

Purple nonsulfur phototrophsPathogenic alphaproteobacteria

Rickettsia Brucella Ehrlichia

Caulobacter

Betaproteobacteria

Pathogenic betaproteobacteria Neisseria Bordetella

Nonpathogenic betaproteobacteria Thiobacillus Spirillum

Gammaproteobacteria

Purple sulfur bacteria Intracellular pathogens

Legionella Coxiella

Methane oxidizersFacultative anaerobes

Family Enterobacteriaceae

Pseudomonads Pseudomonas Azotobacter Azomonas

Deltaproteobacteria

Bdellovibrio

Myxobacteria

Epsilonproteobacteria

CampylobacterHelicobacter

Other Gram-Negative Bacteria

Chlamydias Chlamydia

Spirochetes Treponema Borrelia

Bacteroids Bacteroides