(Chapter 24)

1. Bacteria are microscopic, unicellular, prokaryotic organisms that live in nearly

every environment on earth. Some species are heterotrophs & some are

autotrophs. Shapes include round - coccus, rod - bacillus, spiral - spirillum.

2. Kingdom Archaebacteria:

a) there are a few 100 species of these “ancient” bacteria that live in

extreme habitats where there is usually no oxygen such as: swamps,

deep-ocean volcanic vents, salt lakes, & hot springs

b) biochemical makeup cell membrane & complex genetic makeup make them

unique to other prokaryotes

c) autotrophic species use chemicals such as salt or methane gas food energy

in a process called chemosynthesis

e) heterotrophic species in sewage lagoons play a role in decomposition &

recycling of organic matter

3. Kingdom Eubacteria:

a) more than 10,000 species live in most habitats except extreme ones

b) strong cell walls & a less complex genetic makeup make them unique

c) some heterotrophic species are disease-causing pathogens - they release

poisonous toxins - use of antibiotics/antiseptics interferes with growth

d) cyanobacteria in ponds, streams, & mud contain chlorophyll to trap sun’s

energy to produce food energy with photosynthesis

e) nitrogen-fixing bacteria are chemosynthetic autotrophs - they convert

atmospheric nitrogen in soil into nitrogen compounds plants can use

f) other beneficial species are used to produce foods (cheese, pickles,

yogurt) & medicines (antibiotics)

4. Structural details of bacteria:

a) cell membrane is surrounded by cell wall & some also have a capsule

b) extensions called pili are used for attachment or tranfer of genetic

material & flagella are used for movement

c) floating in cytoplasm is bacterial DNA arranged as a single, circular

chromosome - may also have small loops of DNA called plasmids

d) when conditions are unfavorable some species enclose their DNA in an

endospore until favorable conditions return & growth begins again

(extreme temperatures, harsh chemicals, radiation, drying, etc.)

5. Bacteria can reproduce millions of new cells weekly:

a) asexual reproduction - binary fission - DNA replicates & cell divides to

create 2 genetically identical copies

b) sexual reproduction - conjugation - 1 bacterium transfers all or part of

its chromosome to another bacterium