survey of prokaryotes.pptx

7/28/2019 Survey of Prokaryotes.pptx

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Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Lecture prepared by Mindy Miller-Kittrell, University of Tennessee, Knoxville

M I C R O B I O L O G YWITH DISEASES BY BODY SYSTEM SECOND EDITIONChapter 11 Characterizing and Classifying Prokaryotes


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General Characteristics of Prokaryotic Organisms

Prokaryotes

Most diverse group of organisms

Habitats

From Antarctic glaciers to thermal hot springs

From colons of animals to cytoplasm of other prokaryotes

From distilled water to supersaturated brine

From disinfectant solutions to basalt rocks

Only a few capable of colonizing humans and causing disease


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[INSERT FIGURE 11.1]


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Reproduction of Prokaryotic Cells

All reproduce asexually

Three main methods

Binary fission (most common)

Snapping division

Budding


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Arrangement of Prokaryotic Cells

Result from two aspects of division during binary fission

Planes in which cells divide

Separation of daughter cells




Endospores

Produced by Gram-positive Bacillus and Clostridium

Each vegetative cell transforms into one endospore

Each endospore germinates to form one vegetative cell

Constitute a defensive strategy against hostile or unfavorableconditions

Serious concern to food processors, health care professionals,and governments



Modern Prokaryotic Classification

Currently based on genetic relatedness of rRNA sequences

Three domainsArchaea

Bacteria

Eukarya



Modern Prokaryotic Classification




Survey of Archaea

Common features

Lack peptidoglycan Cell membrane lipids have branched hydrocarbon chains

Classified in three phyla: Crenarchaeota, Euryarchaeota, Korarchaeota

Reproduce by binary fission, budding, or fragmentation

Most are cocci, bacilli, or spiral forms; pleomorphic forms exist

Not known to cause disease



Survey of Archaea

Extremophiles

Require extreme conditions of temperature, pH, and/or salinity tosurvive

Prominent members are thermophiles and halophiles



Survey of Archaea

Extremophiles

Thermophiles

DNA, RNA, cytoplasmic membranes, and proteins do not

function properly below 45C

Hyperthermophiles

require temperatures over 80C



Survey of Archaea



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Survey of Archaea

Extremophiles

Halophiles

Inhabit extremely saline habitats

Depend on greater than 9% NaCl to maintain integrity of cell

wallsMany contain red or orange pigments; require protection from

visible and UV light

Most studied Halobacterium salinarium


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Survey of Archaea



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Survey of Archaea

Methanogens

Largest group of archaea

Convert carbon dioxide, hydrogen gas, and organic acids tomethane gas

Convert organic wastes in pond, lake, and ocean sediments to

methane Some live in colons of animals; one of primary sources of

environmental methane

Have produced ~10 trillion tons of methane that is buried in mud

on ocean floor


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Survey of Bacteria

Deeply Branching and Phototrophic Bacteria

Deeply branching bacteria

Scientists believe these organisms are similar to earliest bacteria

Autotrophic

Live in habitats similar to those scientists think existed on earlyEarth

Aquifex considered to represent earliest branch of bacteria

Deinococcus has outer membrane similar to Gram-negatives,but stains Gram-positive


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Survey of Bacteria

Deeply Branching and Phototrophic Bacteria

Phototrophic bacteriaPhototrophs that contain photosynthetic lamellae; autotrophic

Divided into five groups based on pigments and source ofelectrons for photosynthesis

Blue-green bacteria (cyanobacteria)

Green sulfur bacteria

Green nonsulfur bacteria

Purple sulfur bacteria

Purple nonsulfur bacteria


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Survey of Bacteria

Low G+C Gram-Positive Bacteria

Mycoplasmas

Facultative or obligate anaerobes

Lack cell walls

Smallest free-living cells


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Survey of Bacteria

Gram-Negative Proteobacteria

Alphaproteobacteria

Nitrogen fixers

Azospirillum

Rhizobium

Nitrifying bacteria

Nitrobacter

Purple nonsulfur phototrophs

S f B i


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C i h 2009 d i bli hi j i C i

Survey of Bacteria

survey of prokaryotes.pptx

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