Bacteria Chapter 18 Section 1

Characteristics of Bacteria Prokaryotes- no nucleus Unicellular Live in nearly all environments One circular chromosome Smallest and simplest of all living things Classified by their shape Reproduction: binary fission and conjugation

2 Domains Domain Archaea Domain Bacteria The two domains differ in cell wall composition: Cell walls of Bacteria contain peptidoglycan (which provides strength & gives shape) Cell walls of Archaea do not

Archaea Found in extreme habitats where little else lives. Often referred to as extremophiles. Halophiles – live in very salty areas Thermoacidophiles – live in very hot, acidic areas Many are anaerobes (do not use oxygen) Believed to have helped evolve the first atmosphere into what is seen today.

Eubacteria Vary widely in habitat, found almost everywhere Vary in metabolism/nutrition: Heterotrophic (consumers) Autotrophic (cyanobacteria photosynthesize)

Bacterial Methods of Obtaining Energy Photosynthetic bacteria - food from sun Chemoautotrophic bacteria - food from chemicals (sulfur and nitrogen) Heterotrophic bacteria - decomposers, feed off of decaying organic matter

Oxygen Needs of Bacteria Aerobes – require oxygen Anaerobes – do not require oxygen Obligate anaerobes – cannot live in presence of oxygen Facultative anaerobes – can live with or without oxygen

Classification of Bacteria Can be grouped by shape, cell wall composition, and movement. Shapes: Coccus- round Bacillus- rod Spirillium- spiral Types Strepto- in strands Staphylo- in clusters (grapes) Ex. streptococcus – round in strand-form

Bacteria Characteristics Most bacteria have a cell wall surrounding the cell membrane Some bacteria have a gel like layer called a capsule (provides protection)

Bacterial Movement & Attachment Flagella- move like a corkscrew to help propel Pili- used to stick to surfaces, aids in conjugation (reproduction)

Bacterial Reproduction Binary fission- asexual, clones itself Conjugation- sexual, exchange genetic material, allows for spread of antibiotic resistant genes

Bacterial Survival Some bacteria can survive in unfavorable environments. Survival mechanisms: Endospores – a structure produced by some bacteria when conditions are harsh Ex: bacteria that cause anthrax, botulism and tetanus. Mutations – changes in DNA, may allow bacteria to survive harsh conditions. May also lead to antibiotic resistance.

Disease-Causing Bacteria Only a small percentage of bacteria actually cause disease. 2 ways bacteria can cause disease: Multiply quickly at site of infection before body can destroy them Secrete a toxin or other substance that causes harm. Examples of human bacterial diseases: strep throat, lyme disease, pneumonia, etc.

Antibiotics Different antibiotics interfere with different cell processes Examples: Penicillin, Amoxicillin, Tetracycline Some bacteria have become resistant to antibiotics (due to mutations or over exposure)

Beneficial Bacteria Many foods have bacteria in them (yogurt, swiss cheese) Bacteria are important in nutrient cycling (nitrogen fixing bacteria) Mining companies use chemoautotrophic bacteria to clean up spills Normal flora – helpful bacteria that live in & on you

Practice Problem #1 Tuberculosis is caused by a bacterium, Mycobacterium tuberculosis. Many years ago, streptomycin easily controlled the bacterium. Now streptomycin is much less effective against the resistant M. tuberculosis. The increasing resistance of M. tuberculosis to streptomycin is most likely due to the increased — a. use of streptomycin for bacterial infections b. numbers of alternatives to streptomycin c. artificial production of streptomycin d. early detection of bacterial infections

Practice Problem #2 Which of these could be successfully treated with antibiotics? Strep throat Common cold HIV Influenza

Practice Problem #3 Which of the following choices is not a method of preventing bacterial illnesses from spreading in a meat-processing plant? a. Using antibiotics to treat persons with food poisoning b. Washing hands and utensils with hot soapy water Use of gloves when handling raw meat products d. Treatment of work areas with chemical disinfectants