Bacteria on the Point of a Pin

PROKARYOTESPROKARYOTES::Usually small (< 5 Usually small (< 5 m) compared m) compared to most eukaryotic cells (10-100 to most eukaryotic cells (10-100 m)m)Cell shapesCell shapes: bacilli, cocci, spirilli; : bacilli, cocci, spirilli; Some move by flagella (not 9+2), or by Some move by flagella (not 9+2), or by glidinggliding

The Most Common Shapes of Prokaryotes

The Endospore of Clostridium tetani

EndosporeEndospore

This is the main reason why This is the main reason why bacterial diseases such as bacterial diseases such as Anthrax can last for decadesAnthrax can last for decades. .

REPRODUCTION:Can reproduce as quickly as every 20minutes

Binary FissionBinary FissionBinary Fission

Prokaryote Colonies in Culture (on agar)

Prokaryote Evolutionary History Based on Prokaryote Evolutionary History Based on rRNA Gene SequencesrRNA Gene Sequences::

There are 2 prokaryotic domains: Bacteria & Archaea.The term “bacteria” is not a synonym for prokaryotes.

Table 25.1

The Three Domains of Life

Domain Bacteria:•About 5000 known species; most of the bacteria that “make the news”•Lack organelles except ribosomes•They are ubiquitous!

A Comparison of the Three Domains of Life

Domain ArchaeaDomain Archaea::•methanogensmethanogens produce methane in deep produce methane in deep sea thermal vents & freshwater sea thermal vents & freshwater sediments sediments •halophileshalophiles occupy very saline occupy very saline waters(Dead Sea, Great Salt Lake)waters(Dead Sea, Great Salt Lake)•thermophilesthermophiles live in very hot waters (to live in very hot waters (to 113ºC)113ºC)

(e.g. Yellowstone thermal pools) (e.g. Yellowstone thermal pools) •Evolved 3.5 bya – first cells on earth!

“Heat-loving” Prokaryotes

Specialized Membranes of Prokaryotes

Respiratory Respiratory MembranesMembranes

ThylakoidThylakoidMembranesMembranes

DNA can also be absorbed from DNA can also be absorbed from

another cell--another cell--transformationtransformation, or, or

transferred among prokaryotic transferred among prokaryotic cells by viruses--cells by viruses--transductiontransduction

Some bacteria produce surface Some bacteria produce surface pilipili-- -- tubular structures that attach tubular structures that attach prokaryotic cells to host cells, or to prokaryotic cells to host cells, or to each other during each other during conjugationconjugation--DNA transfer can occur.DNA transfer can occur.

Pili

Prokaryotic Conjugation

Domain BacteriaDomain Bacteria::Walls are formed of Walls are formed of peptidoglycanpeptidoglycan (unlike Archaea).(unlike Archaea).There are two major wall types:There are two major wall types: Gram negativeGram negative Gram positiveGram positive

Escherichia coli

Streptococcus

Gram negative bacteriaGram negative bacteria also have an also have an outer lipid membrane that allows loss of outer lipid membrane that allows loss of purple crystal violet stain by washing. purple crystal violet stain by washing.

Cells can then be stained with a Cells can then be stained with a pinkpink dye.dye.

Outer membrane can confer toxicity & Outer membrane can confer toxicity & antibiotic resistance.antibiotic resistance.

Gram Negative:

Stains pink or red

Gram positive bacteriaGram positive bacteria have more have more peptidoglycan and lack outer lipid peptidoglycan and lack outer lipid membrane; retain violet stain--appear membrane; retain violet stain--appear purplepurple

Gram positive bacteriaGram positive bacteria are more are more susceptible to antibiotics (e.g. penicillin) susceptible to antibiotics (e.g. penicillin) that interfere with peptidoglycan wall that interfere with peptidoglycan wall developmentdevelopment. .

Gram Positive:

Stains violet/blue

1. Autotrophs generate their own 1. Autotrophs generate their own reduced, energy-richreduced, energy-richorganics from carbon dioxide, organics from carbon dioxide, methane, or other inorganicsmethane, or other inorganics

A. Photoautotrophs use A. Photoautotrophs use light light energy & fix COenergy & fix CO22 via via photosynthesisphotosynthesis

B. Chemoautotrophs B. Chemoautotrophs oxidize oxidize inorganicinorganic compounds compounds

2. Heterotrophs use reduced organic 2. Heterotrophs use reduced organic compounds produced by other compounds produced by other organismsorganisms

A. Photoheterotrophs use lightenergy to make ATP, but absorb

organicsB. Chemoheterotrophs obtain

ATP by respiration or fermentation of organic molecules absorbed from environment.(fungi & animals, and some protists& plants also fall into this category)

Chemoheterotrophs that use secreted Chemoheterotrophs that use secreted enzymes to break down dead enzymes to break down dead organisms & organics are organisms & organics are saprobessaprobes..

(some fungi and protists & most (some fungi and protists & most animals animals are also saprobes)are also saprobes)

Chemoheterotrophs that absorb Chemoheterotrophs that absorb organics from living hosts are organics from living hosts are parasitesparasites (one way that bacteria (one way that bacteria cause disease).cause disease).

Lyme disease, a Bacterial Disease (Borrelia burgdorferi) Transmitted by Ticks

Slowing Down Growth:•Sterilization•Radiation•Freezing•Refrigeration•Using preservatives•Pasteurization

Benefits of Bacteria:•Production of Foods (cheese, breads, yogurt,pickles, sauerkraut)•In industry they helpproduce antibiotics, dyes,vitamins,insecticides, cleaners, detergents

Benefits (continued)•Major decomposer•Coliform bacteria produceVitamin K in our intestines•Cyanobacteria are a majorproducer of oxygen in the atmosphere•E. coli is used in biotech

4) The bacteria was cultured on this 4) The bacteria was cultured on this substance . . .substance . . .

5) All of the multicellular protists are5) All of the multicellular protists areof this type. . of this type. .

6) Red tides are caused by. . .6) Red tides are caused by. . .