Bacteria & Viruses

Bacteria The earliest known fossils are of 3.5 billion year old bacteria Most bacteria come in 1 of 3 possible shapes: spherical, spiral, or rod shaped. All bacteria are prokaryotes (they lack a nucleus, chromosomes, & membrane- bound organelles) members of either kingdom archaebacteria or eubacteria

Bacteria cause disease. Bacteria have a cell wall There are 2 different types of cell walls Based on GRAM STAINING, we can determine the type of cell wall it has. One of two types: GRAM POSITIVE: can be treated w/ antibiotics GRAM NEGATIVE: unaffected by antibiotics

Bacterial Reproduction Bacteria reproduce by copying its DNA and then splitting into two identical cells (BINARY FISSION) Each new cell is EXACTLY like the parent cell In some cases, genetic material is transferred from one bacterium to another by a process called CONJUGATION CONJUGATION does NOT increase the number of bacteria, but it does give them more genetic possibilities Ex) This is how some bacteria become RESISTANT to antibiotics.

How Bacteria Obtain Nutrition Some are AUTOTROPHS (they make their own food, usually by photosynthesis) Some that live in the soil & swamps use CHEMOSYNTHESIS (they use the energy in inorganic molecules to make organic molecules) Some are HETEROTROPHS (they feed on dead animals & animal wastes, dead plants, etc. Some heterotrophic bacteria are parasites.)

How Bacteria Affect Humans Some bacteria are decomposers (break down organic matter and return nutrients to the environment) Some are nitrogen-fixing bacteria (make nitrogen available to plants by “fixing” atmospheric nitrogen into ammonia) Some are used to make food (yogurt, sour dough, cheese) and drugs (antibiotics) Some cause disease (PATHOGEN) and contaminate food PASTEURIZATION =heating food to a temp that kills most bacteria

Bacterial Disease Bacteria travel through air, water, and are carried by animals. Sanitation & hygiene help prevent and control the spread of bacterial diseases. VACCINE: a preparation of killed or weakened pathogens introduced into the body to produce immunity ANTIBIOTICS: chemical substances with the capacity to destroy or inhibit the growth of bacteria. ANTIBIOTIC RESISTANCE: happens when a few bacteria with mutant genes are able to resist & thereby survive antibiotic treatment (THEY DO NOT DIE WHEN EXPOSED TO ANTIBIOTICS – THIS IS BAD NEWS)

Virus Viruses are NONLIVING Reproduce by inserting their genetic material into the DNA of a HOST cell. A virus is NOT a cell It is just a core of genetic material ( DNA or RNA ) surrounded by a protein coat. It enters a HOST cell, infiltrates the host cell’s nucleus, inserts its genetic material into the host’s DNA and then begins mass reproduction  eventually resulting in the lysis of the host cell

Viral Diseases AIDS (Acquired Immune Deficiency Syndrome) is caused by HIV (Human Immunodeficiency Virus) HIV is an RNA virus that mutates often AIDS is ALWAYS fatal – there is no cure – there are drugs that can SLOW the disease process, but none to cure it. There are vaccines for smallpox and influenza (these help increase our immunity – but do not guarantee it)