1. Bacteria

2. I. Prokaryotes
Organisms that do not have a nucleus, instead the chromosome is inside a nucleoid.
Different from Eukaryotes, which have a nucleus.
Have one small, circular chromosome called a plasmid.
There are no membranous organelles but they do have ribosomes.
Prokaryotes are ubiquitous (can live almost anywhere)
Prokaryotes have a cell wall that may be surrounded by a capsule.
Some prokaryotes move by flagella, and some adhere to surfaces by using small, hair-like appendages called fimbriae.

3. General Structure

4. II. Archaea
Prokaryotes are split into two domains: Bacteria (or Eubacteria) and Archaea.
Adapted to live in extreme places (ex. heat vents, hot springs, salt lakes)
Plasma membrane contains special lipids to tolerate extremely high temperatures. NO PEPTIDOGLYCAN
Archaea are NOT photosynthetic. Most gain nutrition through “chemosynthesis”. That is, they can “eat” sulfur. Some excrete methane gas, which is a large contributor to the greenhouse effect (global warming).

5. II. Archaea Includes three types of extremophiles:
Methanogens (stomachs of cows, swamps, surprisingly moderate marine environments – use CO2 to oxidize H2 molecules into Methane)
Halophytes (salty environments – carry out photosynthesis using a red pigment)
Pyrophilic acid lovers (temperatures of 60C -105C and pH of 1 to 2 – metabolize inorganic molecules such as sulphur)

6. III. Eubacteria Nutrition: three primary kinds of bacteria:
Heterotrophs – ubiquitous. Break down organic molecules, but cannot hunt those molecules. Some live as parasites, some live is as saprobes (decomposing dead organic matter.)
Photosynthetic autotrophs – Contain chlorophyll a and can photosynthesize. Includes cyanobacterium.
Chemosynthetic autotrophs – Found in soil and water – break down inorganic molecules such as sulfur and nitrogen. Essential to plant health.

7. III. Eubacteria Cellular Respiration
Most bacteria are aerobic, requiring a constant oxygen supply for cellular respiration.
Obligate anaerobes are unable to grow in the presence of oxygen
Facultative anaerobes are able to grow in the presence or absence of oxygen.
Many bacteria are saprotrophs which externally digest organic compounds and absorb nutrients from dead organisms.

8. III. Eubacteria Reproduction
Prokaryotes reproduce asexually by binary fission, and some can form endospores (anthrax).
In order to accomplish genetic recombination (but not sexual reproduction) bacteria can also reproduce by: conjugation, transformation, and transduction.

9. III. Eubacteria
Binary fission: similar to mitosis, DNA replicates and cell divides
Conjugation: one cell passes DNA to another through a pilus
Transformation: cell takes up DNA from its liquid surroundings
Transduction: bacterial viruses carry portions of DNA from one bacteria to another

11. III. Eubacteria Endospore formation:
Bacteria can “hibernate” to avoid unfavorable environmental conditions.
Hibernation is accomplished by saving a small portion of their cytoplasm and a copy of their DNA, and letting the rest of the cell dry out. They are then encased by three layers of spore coats.
When conditions are favorable they rehydrate and form a full bacterial cell again.

12. III. Eubacteria Ecology Bacteria are the decomposers in ecosystems.
Some bacteria are symbiotic and live in association with other organisms.
The bacteria that reside in the human intestinal tract are mutualistic (both benefit); commensalistic (no harm, no benefit) bacteria reside on our skin; and parasitic (only they benefit, we suffer) bacteria cause a wide variety of diseases.
The cyanobacteria are photosynthetic in the same manner as plants.

13. E. Classification Bacteria occur in three basic shapes:
rod (bacillus),
round (coccus),
spiral (spirillum).
Based on a dye test, bacteria are either Gram- positive or Gram-negative: Gram-positive bacteria have a thick layer of peptidoglycan on their cell wall; Gram-negative bacteria have a thin layer.
Gram –positive bacteria are easier to target with vaccines and antibiotics

15. E. Classification Classified by arrangements
Staphylo – grapelike clusters
Diplo – paired cells
Strepto – long chains

16. III. Eubacteria Adaptations for Survival Reproduce Rapidly
High rate of mutation
Can live in extremely diverse habitats
Can exist under adverse conditions – Some Gram + bacteria can form endospores when the environment becomes harsh.

17. G. Importance for Humans
Benefits
Associated with good health – natural part of flora
Nitrogen fixation
Recycling nutrients
Foods and medicines
Disease-prevention
Disease
Some bacteria produce toxins that can damage cells.
Some bacterial proteins cause hypersensitivity reactions which can result in serious illness.

19. H. Antibiotics
Penicillin was the first antibiotic. It is highly effective against Gram+ bacteria, but much less so against Gram- bacteria.
Attacks the sugars that hold the capsule together.
Many bacteria are resistant to antibiotics. High mutation rates and misuse of antibiotics has caused a serious health threat that continues to escalate.