Bacteria

Bacteria Facts

• Bacteria are found nearly EVERYWHERE on Earth!!!!• Have been found at the bottom of ocean trenches• Are on every surface• Have changed into hundreds of thousands of species• Numbers are estimated to be over 5 billion trillion trillion

organisms• The earliest forms are believed to be around 3.5 billion years old• They are “prokaryotes” meaning they have no membrane-bound

nuclei

Bacterial Classification

• Bacteria are classified mainly by:

*structure

*physiology (how they work)

*molecular compostion

*reaction to certain types of stains

Bacteria can be broken down into to two main groups: Archaebacteria and Eubacteria

Kingdom Archaebacteria

• Quite different than other bacteria • They have unusual lipids (fats) in their cell

membranes• They have no peptidoglycan (a carbohydrate found in

cell walls)• They are sometimes called “extremophiles”• Live in extreme environments

Thermoacidophiles

• Live in extremely acidic environments such as hot springs (up to 230 F)

• Live near volcanic vents• Thrive in areas where the pH is less than 2• Live in areas that leak scalding acid water at the

bottom of the ocean

Halophiles

• Salt-loving bacteria

• Found in areas with high salt concentrations

• Great Salt Lake, Dead Sea, etc

• Use salt to generate ATP

Methanogens

• Convert hydrogen and carbon dioxide to methane gas

• Can only live in anaerobic conditions

• Found in “swamp mud”

• Found in the gut of animals

• Produce “gas” we excrete

Kingdom Eubacteria

• “Stereotypical” bacteria• Can be classified by shape and by staining• By shape: • Bacillus (plural: Bacilli) = rod-shaped• Coccus (plural: Cocci) = sphere-shaped• Spirillum (plural: Spirilla) = spiral-shaped• “Streptococci” = cocci occur in chains• “Staphylococci” = cocci occur in clusters

Common Bacteria & Problems

• “Staph” infections….often found on skin. Acne, skin lesions/sores, etc

• “Strep” infections….strep throat, scarlet fever, impetigo, etc.

• Food Poisoning - Escherichia coli infections

Gram Stain Procedure

• Gram positive: Retains Gram stain and appear purple.

• Gram negative: Doesn’t retain Gram stain and appears pink

• Gram positive bacteria have a thicker peptidoglycan layer so they can hold the purple stain

Phylum Cyanobacteria

• Are photosynthetic• Once considered “blue-green algae”• Eutrophication = population increase due to high

availability of nutrients.

Phylum Spirochetes

• Spiral shaped• Heterotrophs• Live freely, symbiotically, or parasitically.• Examples include Lyme disease and the STD

syphilis.

Phylum Gram-Positive Bacteria

• Not all species are Gram positive, a few are Gram negative

• Includes: • species that cause strep throat• species that cause gum disease• Species include some dairy-producing bacteria

Phylum Proteobacteria

• Very large & diverse group

• Includes:

• Enteric bacteria (live in animal guts)

• Chemoautotrophs (extract energy from minerals to make own food)

• Nitrogen-fixing bacteria in soil

Some Phyla of Bacteria and Their Properties

Phylum Shape Motility Metabolism Gram Rxn

Cyanobacteria Bacilli

Cocci

Gliding

Some non-motile

Aerobic

Photosynthetic

autotrophic

Gram negative

Spirochetes Spirals Corkscrew Aerobic

Anaerobic

heterotrophic

Gram negative

Gram Positive Bacteria

Bacilli

Cocci

Flagella

Some non-motile

Aerobic

Anaerobic

Heterotrophic

photosynthetic

Gram positive

Proteobacteria Bacilli

Cocci

spiral

Flagella

Some non-motile

Aerobic

Anaerobic

Photosynthetic autotrophic

Gram negative

Bacterial Anatomy

• Cell wall - gives shape, protection• Cell membrane - regulates movement of materials in/out of the

cell• Cytoplasm - contains DNA and other materials• Chromosomes - genetic material• Plasmid - contains genes obtained through genetic

recombination• Capsule & slime layer - protection• Pilus - attachment to other surfaces• Endospore - protection against harsh environmental conditions• Flagellum - moves the cell

Bacterial Reproduction

• Sexual reproduction called “conjugation”• Involves two bacteria and a “sex pilus”• Results in genetically unique bacteria• Asexual reproduction called “binary fission”• Results in genetically similar/identical bacteria• Can occur very, very quickly