Bacteria

Structure

• One celled organisms that occur alone or in chains or groups

• Three basic shapes– Spheres, called cocci– Rods, called bacilli– Spirals, called spirilla

• Cell contains cytoplasm surrounded by cell membrane and cell wall

• Ribosomes in cytoplasm, too

Structure Continued

• Classified as prokaryotic because they don’t contain a membrane bound nucleus or other organelles

• Genetic material is found in its one circular chromosome in cytoplasm– Some have smaller circular piece of DNA called a

plasmid

Special Features

• Some bacteria have:– Thick, gelatin like capsule

around cell wall for protection and to help stick to surfaces

– Hair-like projections- help stick to surfaces

– Slime layer- enables bacteria to stick to surrounding surfaces and reduce water loss

– Flagella- whip-like tails that help bacteria move

Reproduction

• Fission- process that produces two new cells with identical genetic material to each other and that of the original cell

• Some bacteria exchange genetic material by lining up next to each other and exchanging DNA through a small tube

Obtaining Food and Energy

Producers• Some bacteria contain

chlorophyll or other pigments to make own food using energy from Sun

• Others use energy from chemical reactions

Consumers• Some break down dead

organisms to obtain energy• Others live as parasites of

living organisms and absorb nutrients from their host

Aerobic Vs. Anaerobic

Aerobe• Break down food and obtain

energy through respiration• Most bacteria (and us!)

Anaerobe• Organism adapted to live

without oxygen– Anaerobic bacteria live in

intestinal track of humans– Some bacteria cannot survive

when exposed to oxygen

Kingdoms

• Bacteria classified into two kingdoms– Eubacteria Scientists study many characteristics

to classify eubacteria into smaller groups– Archaebacteria contain bacteria found in

extreme conditions, such as hot springs

Cyanobacteria

• A eubacteria producer that makes own food using carbon dioxide, water, and energy from sun. produce oxygen as a waste. Live in colonies are an important food source for some organisms in lakes, ponds, and oceans. Oxygen produced by them is used by other aquatic organisms. However, can cause blooms that are harmful to organisms

Consumer Eubacteria

• Classified into two categories based on results of Gram’s stain– Bacteria treated with chemical called stain.

• Gram positive bacteria stain purple because they have thicker cell walls

• Gram negative bacteria stain pink because they have thinner cell walls– Composition of cell wall can determine how effective certain medicines

will be against the bacteria

• One group does not have cell walls, allowing them to change shape. One type of these causes pneumonia

Archaebacteria

• One group lives in salty environments like Dead Sea

• Others love hot or acidic environments, living near ocean vents or hot springs

Methane producers

• Some archaebacteria use carbon dioxide for energy and release methane gas as a waste.– They are used in sewage treatment by breaking

down the waste material that has been filtered out

Beneficial Bacteria

• Some bacteria produce chemicals called antibiotics that limit the growth of other bacteria

• Consumer bacteria called saprophytes uses dead organisms as food and energy sources– By helping to recycle nutrients, the nutrients

become available to other organisms

Nitrogen fixing bacteria

• Plants and animals need nitrogen to make proteins and nucleic acids– Plants need nitrogen from the soil or air

• Nitrogen-fixing bacteria change nitrogen from the air into forms that plants and animals can use– Some plants, like peanuts, have nodules that

contain these bacteria

Bioremediation

• Using organisms to help clean up environmental pollutants

• One type uses bacteria to break down wastes and pollutants into simpler harmless compounds– Oil spill cleanup by bioremediation likely to

increase in future

Bacteria and Food

• Bacteria used to make yogurt, cheese, and buttermilk

• Other foods made using bacteria are sauerkraut, vinegar, pickles, olives, soy sauce

Other Uses of Bacteria

• Medicines, enzymes, cleansers, adhesives

• Methane gas produced by bacteria used as fuel for heating, cooking, and industry, as well as breaking down plant and animal material

Harmful Bacteria

• Not all bacteria is good!• Pathogen- any organism that causes disease– Bacteria causes strep throat, whooping cough,

anthrax, botulism, and more

Bacteria and Toxins

• Some bacteria produce poisonous substances known as toxins– Ex: botulism a type of food poisoning that can cause

paralysis or death• When growing conditions unfavorable, bacteria

can produce thick-walled structures called endospores, which can exist hundreds of years before resuming growth– Commercially canned food undergo process that uses

steam at high pressure to kill bacteria and endospores

Pasteurization

• Unless it’s been sterilized, all food contains bacteria

• Pasteurization process of heating food to a temperature that kills most harmful bacteria but causes little change to taste of food– ex: milk, some fruit juice, yogurt all pasteurized

Treating Bacterial Diseases• Bacterial diseases usually

treated with antibiotics.– Penicillin, an antibiotic,

prevents bacteria from making cell walls

• Vaccines made from damaged particles taken from bacteria cell walls or dead bacteria. When vaccine injected, white blood cells recognize bacteria so that if it enters body again, white blood cells will attack it