Bacteria Biology 20 Blue Green Algae Diagram of Bacteria Salmonella Bacteria Biology 20

Common Bacteria Belong to the Domain Bacteria and Kingdom Eubacteria They are microscopic prokaryotes. Organisms are classified as bacteria by one characteristic: the lack of a cell nucleus. They are the most numerous organisms on Earth. There are more bacteria on or in your body than there are people in the world!

Bacteria Relatively few species of bacteria cause infection. Hundreds of species of bacteria live on the human body and within the gastrointestinal tract (critical to human well-being).

Bacteria They have evolved into many different forms and are part of every environment on Earth. For example, there are: Aerobic organisms that need oxygen to survive. Anaerobic organisms that die in the presence of oxygen. Autotrophic organisms that produce their own food. Heterotrophic organisms that get their nutrition from other organisms.

Kinds of Bacteria Currently identified using DNA but historically the shape and arrangement of bacteria identified them Three basic shapes: round, rod-shaped, or spiral Spherical (coccus) Rod-shaped (bacillus) Spiral (spirillum) Shape

Kinds of Bacteria Diplo – paired Staph – in clusters Strep – in chains Spirillum only live as single cells. Some coccus form pairs and chains while others grow in grape like bunches. Some bacilli also form pairs or chains but they do not grow in bunches. Diplo – paired Staph – in clusters Strep – in chains Arrangement

Characteristics Prokaryotic cell Singular circular chromosome Cell wall containing peptidoglycan Lacking nuclear envelope Lacking organelles and cytoskeleton

Structure Structures that help bacteria survive in hostile environments Capsules (slime layers) – protects the cell from drying out, helps evade immune system and adhere to surfaces Pilli – hair-like projections that help cells attach to surfaces Endospores – bacteria become dormant until conditions become favourable  

Structure Structures that help bacteria move Flagella – one or more tail- like structures

Reproduction Occurs most often by an asexual process called binary fission One cell splits into two cells; offspring are genetically identical to parents Can occur in under 20 minutes; producing 1 billion bacteria in under 10 hours

Reproduction Can also occur through bacterial conjugation Two cells attach to each other and exchange genetic information; offspring have new genes and new traits Only between bacteria in the same or closely related species

Photosynthetic Bacteria Cyanobacteria commonly called blue- green algae the oldest known fossil (>3.5 billion years old!) responsible for many Proterozoic oil deposits cyanobacterial blooms common on prairie sloughs – can harm livestock, pets, and humans

Gram-negative bacteria Few organisms have the ability to utilize atmospheric nitrogen. Nitrogen-fixing bacteria within the root nodules of certain plants provide a usable source of nitrogen to plants. E.g. Rhizobium, Pseudomonas

Bacteria & Health Only a small percentage of bacteria cause disease in humans. Bacterial diseases include: gonorrhea, chlamydia, strep throat, pneumonia, acne, botulism, food poisoning, Lyme disease. Bacteria can also cause disease in plants and animals.

Eubacteria & Archaebacteria

Archaebacteria Classified in Domain and Kingdom Archaea Thought to be more ancient than bacteria and yet more closely relate to eukaryotes Their cell walls do not contain peptidoglycan and they have some of the same proteins as eukaryotes.

Archaebacteria There are diverse in shape and nutrition. Some are autrophic, but most are heterotrophic. They are referred to as “extremophiles” because they can live in extreme environments: boiling hot springs, salty lakes, thermal vents on the ocean floor, and marsh mud where there is no oxygen.

Characteristics Prokaryotic cell Singular circular chromosome Cell wall without peptidoglycan Membrane lipids Lacking nuclear envelope With organelles and cytoskeleton

Methanogens Typically found in swamps and marshes Produce methane gas as a by-product of metabolism

Thermoacidophiles Resistant to hot temperatures and high acid conditions Found in acid hot springs, acidic soil, and deep ocean volcanic vents