Chapter 20 Section 1 Bacteria

There are two major groups of bacteria Two Types of Bacteria There are two major groups of bacteria Domain Archae Domain Bacteria

Archeabacteria Older than eubacteria Contain unusual lipids in cell wall and introns in their DNA- both are lacking in eubacteria Known for living in extreme conditions Examples: Methanogens: anaerobes that make energy by converting H2 and CO2 into methane gas Extreme halophiles: thrive in environments w/high salt content. They use salt to make ATP Thermoacidophiles: live in highly acidic, hot environments.

Eubacteria Most known prokaryotes are members of the Domain Bacteria. Found everywhere Occur in three shapes Cocci (pl) Coccus (sing) are spherical or round in shape Bacilli (pl) Bacillus (sing) are rod shaped Spirilli (pl) Spirillus (sing) are cork screw shaped

The Gram Stain Bacteria are classified partly due to the way that they react to a Gram Stain Gram positive bacteria dye purple (they have a thick layer of peptidoglycan and no outer membrane) Gram negative bacteria dye pink/red (they have a thin layer of peptidoglycan and have an outer membrane) Gram positive bacteria and Gram negative bacteria differ in their cell wall structure. This difference impacts which stain they will absorb.

Obtaining Energy Some bacteria are: Photoautotrophic: use light to make energy, photosynthetic Ex. Sulfur and nonsulfur bacteria and cyanobacteria Chemoautotrophs: get there energy from inorganic sources Heterotrophs: get there energy from other organisms. Heterotrophs can be broken down into: Anaerobic: do not need oxygen to survive Obligate anaerobes: will die if exposed to oxygen ex. methanogens Obligate aerobes: require oxygen to survive ex. Tubercullosis (TB) Facultative anaerobes: live w/ or w/o oxygen ex. E. coli

Prokaryote Reproduction Reproduce through binary fission Exchange of genetic material through conjugation, transformation, and transduction; and survive harsh conditions by forming endospores

Types of Genetic Recombination Reproduction Transformation: In transformation a bacterial cell will take up free floating genetic material from the surrounding environment. Conjugation: one bacteria shares genes contained in a plasmid with another bacteria through a pilus (sing) pili (pl) Transduction: a virus takes up a piece of a host bacteria’s DNA during infection When new viruses form they have the piece of bacterial DNA in their DNA When the new viruses infect another DNA they will insert their new DNA along with the piece of bacterial DNA into the host bacteria Transduction occurs during the lysogenic and lytic cycle of virus reproduction

Bacteria Toxins Two Types: 1. Endotoxins: are composed of lipids and carbohydrates. They are part of the cell membrane of Gram negative bacteria. They are released when the bacteria dies Ex. E. coli causes illness through endotoxins 2. Exotoxins: are proteins produced by Gram positive bacteria Ex. Diptheria causes illness by releasing exotoxins Ex. Botulism causes illness by releasing exotoxins

Disease Bacteria cause illness through toxins (endotoxins and exotoxins) and enzymes Digestive enzymes are released by bacteria to open up tissue to further invasion Ex. Streptococci (strep throat) releases enzymes that destroy blood clots

How do antibiotics work? Antibiotics are chemicals that kill bacteria by interfering with their life functions (Table 24-5) Penicillin inhibits cell wall synthesis Rifampin interferes with RNA synthesis

Bacterial Resistance There are two main causes: Antibiotics are prescribed for viral diseases Anitibiotics are not used properly Some bacteria possess a genetic mutation that renders them less susceptible to the antibiotics. These bacteria are said to be antibiotic resistant.

Good or Bad? Not all bacteria are bad Some plants contain bacteria in their roots that fix nitrogen. Legumes such as soy and peanuts have this ability Bacteria are important in the process of decay Bacteria play a necessary role in the creation of some food Ex. Yogurt, buttermilk, sauerkraut

Bacteria vs. Viruses Bacteria are: Viruses are: Living organisms Capable of making or obtaining energy Completely different in structure Viruses are: Not living organisms Not capable of making or obtaining energy (they don’t need to)