Bacteria Bacteria live in almost every environment on Earth, from arctic ice to volcanic vents. 1 cm 2 of your skin has 100,000 bacteria on it. 1 teaspoon of soil has over 1 billion bacteria in it.

Characteristics of Bacteria All bacteria are single-celled. All bacteria are prokaryotic (lack nucleus and membrane-bound organelles). All bacteria reproduce asexually by binary fission. All bacteria contain DNA arranged into a single circular chromosome.

Structure of Bacteria Size = 1 to 10 µm (1000 µm = 1 mm) 1. capsule 2. cell wall 3. cell membrane 4. DNA 5. pilus 6. cytoplasm 7. flagellum 8. ribosome 9. plasmid

Structure of Bacteria 1. Capsule: – a sticky protein cover found in some bacteria 2. Cell wall: – a protective coating of all bacteria 3. Cell membrane: – controls entry of molecules 4. Circular chromosome of DNA [not enclosed in a nucleus] 5. Pilus: - a protein tube that attaches to other bacteria 6. Cytoplasm: - contains ions & molecules 7. Flagellum: - whip-like tail for movement 9. Plasmid: - small loop of DNA which contains a few genes 8. Ribosomes: - needed for protein synthesis

3. Bacteria Reproduction a. Binary fission 1. Single circular chromosome replicates 2. Attached loops remain near center of cell 4. Cell pinches in between chromosome loops 5. New cell wall forms to produce two separate cells 3. Replicated loops drift apart

b. Endospore formation 1. Occurs only with gram-positive bacteria. 2. When growth conditions become unfavourable 3. Bacterium makes an endospore (a thick wall that surrounds its DNA and cytoplasm). 4. The endospore can lie dormant for a long time, through drought, heat and radiation, until good conditions return

c. Conjugation Conjugation of E. coli 1. Occurs when conditions are less than ideal due to shortages of food or space or exposure to new chemicals. 2. Two bacterial cells connect via a bridge (a pilus) and exchange a plasmid (a small ring of DNA). 3. Conjugation increases the genetic variability in a population of bacteria. 4. Conjugation is the cause of the spread of anti-biotic resistance.

4. Classification of Bacteria a. Classification by shape: Cocci (round) Bacilli (rod-shaped) Spirilli (spiral) Staphylo (clusters) Strepto (chains) Diplo (pairs)

b. Classification by Gram Stain: Gram-negative: stained pink these bacteria have a thin cell wall and many are pathenogenic [cause disease] Gram-positive: stained purple [after a dyeing technique with crystal violet and iodine] these bacteria have a thick cell wall and are mostly harmless

5. Bacteria Nutrition Heterotrophic: must eat others for food Autotrophic: able to make own food (photoautrophic or chemoautotrophic) Phototrophic bacteria only grow in the light. Heterotrophic and chemotrophic bacteria do not change metabolism in light or dark.

6. Bacteria respiration a. Obligate Aeorbe: must have oxygen to produce energy from food b. Obligate Anaerobe: can not survive in the presence of oxygen, but can still produce energy from food in absence of oxygen c. Facultative anaerobe: can survive with or without oxygen

7. Bacteria in Ecosystems a. Nitrogen fixation: b. Carbon-Oxygen Cycle: Some bacteria take nitrogen directly from the air to make proteins These bacteria usually live in nodules on roots of legumes Bacteria are key in the breakdown of dead organisms and the release of carbon dioxide back into the atmosphere

8. Bacteria and Disease Many pathogenic bacteria produce toxins that cause disease symptoms Some make people ill and some are fatal

Salmonella a. Endotoxins: produced inside bacteria and are only released when gram-negative bacteria split they are seldom toxic, but do cause fever, diarrhea, and vomitting

Clostridium b. Exotoxins: produced and excreted from living bacteria they do not produce fevers, they are often fatal

The Deadliest Bacterium The bacterium Yersinia pestis caused the Bubonic Plague (Black Death) in the 14th century. Between 1347 and 1351, 75 million people died, 1/3 of northern Europe.