Bacteria Our invisible friends

Bacteria are prokaryotes Pro – before Karyon – nucleus The simplest forms of life are prokaryotes. Earth’s first cells were prokaryotes.

Lots of Them! Prokaryotes are Earth’s most abundant life forms. They can survive in many environments. They can get energy from many different sources.

Kingdoms Bacteria fall into two kingdoms: Archaebacteria (Archaea) Eubacteria

Archaebacteria Archae = early or primitive In fact archaebacteria have a more advanced structure than eubacteria and share characteristics with eukaryotes Cell wall lacks peptidoglycan Genes and enzymes behave more like Eukaryotes Cells have three RNA polymerases like eukaryotes

Archaebacteria Many Archaebacteria are often referred to as extremophiles. They have the unique ability to survive in environments where other organisms cannot survive. These extreme environments are anaerobic (lacking oxygen) and are believed to resemble conditions that existed when life first evolved on earth, billions of years ago.

Archaebacteria Three major groups of archaebacteria include: Methanogens – methane-producing organisms Extreme Thermophiles – thrive in temperatures up to 110°C Extreme Halophiles – thrive in very salty environments

Eubacteria True bacteria More primitive than archaebacteria Cell wall made of peptidoglycan Cells have only one RNA polymerase

Similarities Common characteristics of Archaebacteria and Eubacteria: Cells are prokaryotic, all are single celled Cells contain no membrane-bound organelles Cells reproduce asexually by binary fission or sexually by conjugation

Eubacteria Classified by Shape Cocci (ball-shaped) Streptococcus mutans Bacillus (rod-shaped) Clostridium botulinum Spirilli (spiral-shaped) Treponema palladium

Eubacteria Classified by Shape

Reproduction & Growth Asexual Reproduction – only one parent is involved Binary Fission – simpler than mitosis. Single stand of bacterial DNA replicates This identical genetic material is transferred to each new cell Bacterium produces a cross wall and divides into two identical cells

Binary Fission

Reproduction & Growth Sexual Reproduction – two parents involved Not common in bacteria Conjugation Transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells The recipient cell now has an altered set of characteristics, due to recombination of the DNA

Conjugation

Factors Influencing Bacterial Growth Physical Factors: Nutritional Requirements: Temperature Energy source Oxygen Carbon pH Nitrogen Osmosis Water Other Minerals Organisms having complex nutritional requirements and needing many growth factors are said to be fastidious

Harmful Effects of Bacteria Bacteria are best known for being: pathogenic - disease causing. The anthrax causing bacteria Bacillus anthracis was the first bacterium proven to cause disease.

Virulence Factors Virulence factors are molecules expressed and secreted by bacteria that enable them to achieve the following: Immunoevasion, evasion of the host's immune response Immunosuppression, inhibition of the host’s immune response Entry into and exit out of cells Obtain nutrients from the host

Symptoms Bacteria cause disease in three major ways: Their sheer numbers burden the host’s tissues and interfere with normal function The bacteria cells destroy the hosts cells and tissues Some bacteria produce poison called toxins which shut down the hosts tissues

Spread and Protection Infectious bacterial diseases are spread from one individual to another in a variety of ways: Moisture droplets in the air Dust Direct contact Fecal contamination Animal bites wounds

Spread and Protection Most people have built in protection provided by the body’s own defense mechanisms: Immune System Other methods of protection include: Sterilization/disinfection Use of antiseptics Extermination of animals that carry bacterial disease Immunizations and administration of antibiotics

Examples of Pathogenic Bacteria Type of Bacteria Disease/destruction produced cloasridia botulism, tetanus, and gangrene streptococci strep throat, scarlet fever, and pneumonia staphylococci boils, food poisoning, and skin infections lactobacilli souring of milk pseudomonads gasoline spoilage bacilli destruction of silkworms staphylococci and pseudomonads food spoilage coliform bacteria Pollution of water sources, soft rot in plants, gastroenteritis and dysentery in humans spirilla cholera and syphilis

Bacteria: Friend or Foe? The usefulness of bacteria far outweigh the damage they cause. One of the most important jobs of bacteria are the recycling they do as decomposers. Bacteria are the primary organism responsible for converting dead plants and animals into natures raw materials. These nutrients are essential for living plants and animals.

Beneficial Effects of Bacteria Type of Bacteria Beneficial Effects clostridia production of butanol and acetone from molasses acetobacter production of vinegar from alcohol intestinal bacteria food digestion; synthesizing of vitamins in humans eg. To regulate blood clotting lactobacilli production of lactic acid form sugar aztobacter, nitrobacter fixation of nitrogen in soils streptococci, lactobacilli production of dairy products eg. Cheese, buttermilk, and yogurt streptomyces source of antibiotics eg. Streptomycin, terramycin, neomycin, and erythomycin

Bacteria Cleaning Crew Some bacteria literally 'live on oil,' just as some people live on meat and potatoes. And they consume it with just as much relish. Such bioremediation cannot only help to clean up oil spills, but also chlorinated chemicals and leaks from storage tanks.

Probiotics Probiotics - live microorganisms that are healthy for the host organism Lactic acid bacteria (LAB) and bifidobacteria are the most common types of microbes used as probiotics Probiotics are commonly consumed as part of fermented foods including: Yogurt Dietary Supplements Buttermilk

Antibacterial Resistance Over the past 50 years, many disease-causing bacteria have slowly developed resistance to antibiotics This resistance arises due to variations within a bacterial population allowing for natural selection

Antibacterial Resistance Bacteria resistant to antibiotics contain R (resistance) Factors These R factors are plasmids with special genes that code for enzymes which inactivate specific drugs The R factors are transferred and recombined in conjugation “The misuse of antibiotics could cause serious problems for society”