Ch 9, Sec 2 Bacteria Bacteria was discovered in the 1600’s by - Anton van Leeuwenhoek (Lay vun hook) - Dutch merchant, made microscopes as hobby - looked at teeth scrapings one day, noted wormlike organisms (not able to see details of organisms due to microscope not strong enough) Bacteria - single celled organisms

Cell Structure - prokaryotes - genetic material inside cytoplasm, no nucleus - most have rigid cell wall, like plant cell, with cell membrane inside - Flagellum - long, whiplike structure to help cell move (like a propeller) - not all bacteria have flagella (moved by air, water, objects) - some have many flagella

Cell Sizes & Shape - bacteria come in many different sizes - strep throat bacterium are from 0.5 – 1 micrometer in diameter - Basic shapes of bacteria - spherical, rodlike, or spiral - determined by chemical makeup Food & Energy - bacteria live in different environments (hot vs cold adaptability) - *All bacteria must have food and ability to break down food for energy

- Obtaining Food - some bacteria: autotrophs, make own food by capturing sun light or from chemical substances - some bacteria: heterotrophs, consume other organisms or food from other organisms (consume milk, meat, decaying leaves) - Respiration - bacteria need energy - most need oxygen to break down food into energy (respiration) - Escherichia coli living in intestines do not need oxygen for respiration

Reproduction - *when bacteria have enough food, right temperature, & suitable conditions, they thrive and reproduce frequently - Under ideal conditions, some bacteria can reproduce every 20 minutes - Asexual Reproduction - reproductive process that involves only one parent & produces offspring identical to parent - binary fission: cell duplicates genetic material, then divides into 2 separate cells

- Sexual Reproduction - two parents combine genetic material to produce new organism, which differs from parents - Conjugation - one bacterium transfers some genetic material to another bacterium through a threadlike bridge; after transfer, cells separate - results in bacteria with new combinations of genetic material

- Endospore Formation - when conditions are no longer favorable for bacteria to grow, some survive by forming endospores - Endospore - small, rounded, thick-walled, resting cell that forms inside a bacterial cell - Endospores can survive without nutrients - They are resistant to ultraviolet radiation, desiccation, high temperature, extreme freezing and chemical disinfectants -Common anti-bacterial agents that work by destroying vegetative cell walls don't work on endospores - commonly found in soil and water, where they may survive for long periods of time

- Endospores can survive for many years - Clostridium botulinum (bacteria that causes botulism) produce heat-resistant endospores that can survive in improperly canned food - because they’re light, a breeze can carry them to new places; if suitable conditions, opens up & bacterium grow & multiply Not all bacteria are harmful - *Bacteria are involved in oxygen & food production, environmental recycling & cleanup, and in health maintenance & medicine production

- Oxygen Production - autotrophic bacteria produce oxygen, scientists think autotrophic bacteria were responsible for first adding oxygen to Earth’s atmosphere billions of years ago - distant offspring of the bacteria help keep oxygen levels in the air stable - Food Production - cheese, sauerkraut, pickles (from bacteria) - some bacteria causes food to spoil; heating & refrigerating slow down food spoilage

- Pasteurization - heating food to a temperature high enough to kill most harmful bacteria without changing taste of food - named after inventor: Louis Pasteur Decomposers - organisms that break down large chemicals in dead organisms into small chemicals - nature’s recyclers - decomposing bacteria break down chemicals in dead leaves - nitrogen-fixing bacteria live in soil & certain root plants; convert nitrogen gas from air into nitrogen products plants need for growth

- Environmental Cleanup - some bacteria convert poisonous chemicals in oil into harmless substances - Health & Medicine - bacteria in intestines help with digestion of food - compete with harmful bacteria for space & prevent them from attaching to intestines - 1970; first medicine-producing bacteria made. Human insulin made by manipulating bacteria’s genetic material