CH 9, SEC 2 BACTERIABacteria 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