Chapter 23

 Cellular organisms  In one of two domains: Archaea and Eubacteria  Generally smaller than eukaryotes  Most are unicellular, some form colonies or filaments  No membrane-enclosed organelles  Ribosomes are located in the cytoplasm  In some – the inner plasma membrane is extensively folded inward to provide reaction sites  Most have a cell wall

 Cocci – spherical Single cells Groups of two: diplococci Long chains: streptococci Clumps: staphylococci  Bacilli – rod-shaped In single rods or long chains  Spiral: Spirochete – flexible spiral Spirillum – rigid spiral  Vibrio – spirillum shaped like a comma

 Provides shape and stability  Allows the cell to inhabit hypotonic surroundings without bursting  Does not help in hypertonic solutions – most bacteria do not grow well in foods preserved with high sugar or salt content  In eubacteria the cell wall contains peptioglycan

 Gram-positive bacteria: Appear blue or violet Cell walls with a very thick layer of peptidoglycan Disease causing gram-positive bacteria are easily killed by penicillin which interferes with peptidoglycan production  Gram-negative bacteria: Appear red or pink Cell walls have two layers: a thin peptidoglycan layer and a thick outer membrane

 Capsule – a slime layer that surrounds the cell wall in some species May provide pathogenic bacteria protection May also allow some bacteria to attach to surfaces (e.g.: to cause dental plaque)  Pili – short, hair-like projections of protein which allow bacteria to adhere to each other or other surfaces  Flagella – longer projections found in mobile bacteria

 In cytoplasm, not surrounded by a membrane  In most, a singular circular chromosome  Most bacteria also contain smaller circular plasmids which may contain genes that code for enzymes, genetic exchange, or antibiotic resistance

 Asexual: Binary fission – DNA replication followed by a transverse wall separating the two new cells Budding – a bulge forms and matures, eventually separating from the original cell Fragmentation – walls develop within a single cell which then separates into several different cells  Genetic exchange: Transformation – fragments of DNA released by one cell are picked up by another Transduction – a phage (form of a virus) carries bacterial DNA from one to another Conjugation – two different bacterial cells exchange genetic material

 Some bacterial form dormant, extremely durable cells in response to unfavorable environmental conditions  Tetanus, gas gangrene, anthrax can all form endospores

 Heterotrophs – most bacteria obtain energy from surroundings: Chemoheterotrophs – decomposers and pathogens Photoheterotrophs – get carbon from other organisms but have chlorophyll to trap sunlight energy  Autotrophs – manufacture their own organic molecules Photoautotrophs – use photosynthesis Chemoautotrophs – use chemosynthesis

 Archaea: No peptidoglycan in cell walls Many live in extremely harsh environments: no oxygen, high salt, or high temperatures  Eubacteria: Peptidoglycan in cell walls Widely distributed and better known

 Decomposers Recycle chemical nutrients necessary for life Especially important in the nitrogen cycle  Pathogens Exotoxins - poisons produced by the bacteria that cause the damage Endotoxins – components of the cell walls that affect the host only when released from the dead bacteria  Food production Microbial fermentation – yogurt, pickles, olives, sauerkraut, vinegar, soy sauce  Antibiotic production  Genetic engineering  Bioremediation