What are Bacteria? Bacteria are PROKARYOTES –The smallest known living cells They are found everywhere!! Bacteria on head of a pin Starr, 317 Bacteria in dental plaque microbeworld.org Did you know? There are over 80 species of bacteria in your mouth!

Some cause disease We call these “pathogens” Anthrax, as seen by Koch microbeworld.org But most are beneficial Bacteria ferment cheese Schraer, 641

Characteristics of Bacteria Most have a cell wall Many have a capsule ( jelly or slimy coating outside the cell wall, for protection) They have a single, circular chromosome. Some have plasmids (tiny rings of DNA separate from the chromosome.) Cytoplasmic Pili help them talk to other cells. Schraer, 632

Some have flagella - made of rope-like proteins, not microtubules. Some slide on a slimy secretion. Many can form dormant cells called endospores to survive harsh conditions. Salmonella Streptomyces spores Many can MOVE

Three basic shapes Spherical – coccus Rod – bacillus Coiled - spirillum Schraer, 633

Simple Colonies Staphylo = clusters Strepto = chains Staphylococcus wisc.edu Diplo = double Diplococcus cat.cc.md.us Streptobacillus

Normal bacterial reproduction 1) chromosome replicates 2) copies separate as cell wall lengthens 3) cell membrane pinches in 4) septum/new wall grows 5) cells divide Steps in binary fission maricopa.edu Bacillus dividing by fission SixKingdoms.html Binary fission (for a quick clone)

How Bacteria Populations Grow!! Growth Curve (in Culture) Schraer, 634

See Fission in Action Did you know? In ideal conditions, some species can divide every 10 MINUTES. What stops them? They run out of food or space, or wastes build up and poison them.

Metabolic Needs Respiration –Most are obligate aerobes. –Others are facultative or obligate anaerobes. -Anaerobes make a variety of fermentation products: -acids, alcohols, methane gas -food products

Nutrition Most are heterotrophs - saprobes or parasites Autotrophs -photosynthetic or chemosynthetic Did you know? Chemosynthetic bacteria are the base of the food chain at ocean floor vents.

Little is Better!! Metabolism is FAST Bacteria can absorb nutrients and secrete wastes rapidly because of high surface-to-volume ratio Did you know? Lactose fermenters break down 10,000 times their weight in lactose in an HOUR!

Two Kingdoms of Bacteria Kingdom Archaebacteria - “Ancient”, most primitive earliest known form of life - Kingdom Eubacteria - includes bacteria and cyanobacteria (blue-green) Fluorescent micrograph of an archaeon microbeworld.org

Kingdom Archaebacteria Why a separate kingdom? Archae differ chemically from other bacteria. 1) cell wall - different amino acids and sugars. Eubacteria have peptidoglycan Archaebacteria have varied polysaccharides but not peptidoglycan. 2) membrane lipids 3) ribosomes 4) enzymes > 5) cytochromes 6) gene sequences... And MORE RNA polymerase

Archae are extremophiles Live in habitats like early earth Too harsh for most organisms 1) methanogens – decomposers, live in intestines, swamps & bogs sewage treatment 2) Halophiles – “love salt” Great Salt Lake, Dead Sea 3) Thermophiles – hot springs, geysers 4) Acidophiles – Guess where? Starr,635

Kingdom Eubacteria Photosynthetic – 2 groups 1) cyanobacteria (aerobes) –Have chlorophyll a and phycocyanin (blue) –Other colors, too –Most live in fresh water –Others live in salt water, soil and lichens Starr, 315 Nostoc Schraer, 637

More photosynthetics 2) green-sulfur and purple bacteria - anaerobic - colors range from pink to black - photosynthesize without water - make no oxygen - live in pond and sea mud

Nitrogen-fixing Fix nitrogen in special cells called heterocysts Chemosynthetic make glucose using energy from chemical compounds Starr, 745 Legume roots – nodules contain nitrogen-fixing bacteria Tube worms at ocean vent Fed by chemoautotrophs Starr, 314

Heterotrophic Bacteria Many groups and types, but divided into two classes by GRAM STAIN Gram positive Purple Respond to normal antibiotics Gram negative Pink - Cell wall resists stain Harder to treat if pathogenic Schraer 637

Biologic Importance of Bacteria 1)Essential to nutrient cycling 2)Decomposers – in soil, inside animals Enterobacteria – live inside us, break down waste, make vitamins 3) Process foods – cheese, yogurt, pickles 4) Some MAKE antibiotics (streptomyacin) 5) Used in cell and molecular research, genetic engineering, medical research..

Sources Schraer and Stoltz, Biology, the Study of Life, 7th ed. Prentice-Hall, 1999 Starr, Cecie, Biology, Concepts and Application, Wadsworth Group, 2003 Fission Archaebacteria Staphylococcus Conjugation Legume nodules Salmonella Bacteria reproducing n/Readings/SixKingdoms.html n/Readings/SixKingdoms.html Dental plaque Fission time-lapse Diplococcus