Biology 106 Lecture Topic # 17: Diversity- Monera Page 1 of 2

I. Prokaryotes and the Evolution of Metabolic Diversity

A. Bacteria

1. Oldest living group of organisms

2. Lived and evolved alone for 2 billion years

3. Most abundant organisms!!

4. In terms of numbers and metabolic impact, they still dominate the biosphere.

a. responsible for creating our oxygen atmosphere

b. decomposers- nutrient cycles and soil building

c. fix atmospheric nitrogen into usable form

d. break down organic nitrogen cmpds into elemental nitrogen, complete nitrogen cycle

e. industrial processes, chemical syntheses

B. Morphology

1. Monera (Greek) "moneres"

2. most bacteria single cells but many form colonies

3. cell shape diversity a. cocci = spheres, b. bacilli = rods, c. spirilla = spirals

4. nearly all prokaryotes have cell walls external to their plasma membranes

Cell wall is a polysaccharide network w/polypeptide crosslinks = peptidoglycan

5. Gram stain -valuable tool for identifying bacteria

a. gram positive = simpler cell walls, large amounts of peptidoglycan.

b. gram negative = structurally more complex cell walls, lesser amounts of peptidoglycan.

6. Some bacteria also secrete sticky substance = capsule,outside of cell wall that aids in adherence to a substrate or each other.

7. Some bacteria also form pili = surface appendage, helps to adhere to each other or substrate.

a. specialized pili used for exchange of DNA

8. Some bacteria form endospores in response to unfavorable environment

a. endospore = chromosome replicated, and one copy surrounded by a durable wall.:

i. desiccation resistant,

ii. remain dormant for centuries

iii. resists boiling temperatures

9. Some bacteria do not form endospores & still survive extreme conditions, ex.

10. Many bacteria are motile, ex.

C. Prokaryote Genome

1. about 1/1000 DNA as Eukaryote

2. conc. as a snarl of fibers = nucleoid region

3. one dbl stranded DNA molecule in form of a ring with little protein

4. Some may have smaller rings of DNA called plasmids

a. only few genes

b. prokaryotes can survive w/o plasmids

c. plasmids replicate separately from main chromosome

d. plasmids readily transferred between partners when bacteria conjugate

D. Bacterial Reproduction

1. Neither mitosis or meiosis

2. BINARY FISSION w/ DNA being synthesized almost continuously

3. Circular DNA replicates, forming 2 circles that are attached to different point on the membrane, and go to different daughter cells

4. Three Mechanisms of Genetic Recombination

a. Transformation = genes are taken up from the surrounding environment

b. Conjugation = genes are transferred directly from one bacterium to another bacterium

c. Transduction = genes are transferred between bacteria via viruses

ALL GENE TRANSFER ONE WAY!! and involve variable amounts of DNA

E. Metabolic Diversity - greater in Monera than all Eukaryotes combined!

1. Photoautotrophs = harness light energy to synthesize organic comps from CO2

ex.'s, cyanobacteria, algae, plants

2. Photoheterotrophs = use light to generate ATP, but obtain carbon in organic form (not synthesized) ex., restricted to Prokaryotes

3. Chemoautotrophs = need CO2 as a carbon source, but obtain energy by oxidizing inorganic substances such as H2S, NH3, FE ++ or some other chemical

ex., unique to Prokaryotes

4. Chemoheterotrophs = must consume organic molecules for both energy and carbon

ex. Prokaryotes, protists, fungi, animals and MOST bacteria are in this group

5. Another category used to divide Prokaryote

Metabolism is the Effect of Oxygen on the Organism

a. Obligate Aerobes = use O2 for respiration and cannot grow w/o it

b. Facultative Aerobes = use O2 if present, but can also grow by fermentation

c. Obligate Anaerobes = poisoned by O2

F. Classification of Bacteria

1. More than 5000 known species

2. Most not based on evolutionary relationships

a. diversified too long ago

b. genealogy difficult to outline

c. potential for unrelated genera to exchange genes via transformation and transduction.

d. microfossils not easy to examine

3. Comparisons of ribosomal RNA have led to divisions into 20 major groups

4. Two major groups which diverged very early in the history of life

a. Archea (formerly known as Archeabacteria)

- distinct from others

- RNA polymerase and ribosomal proteins are Eukaryote like

- cell walls lack muramic acid

- oldest life forms, tackle extreme environments

ex.'s, Methanogens =

Extreme halophiles =

Extreme thermophiles =

b. Bacteria (formerly known as Eubacteria)

i. Gram negative rods, heterotrophs,important pathogens, ex.

ii. Cyanobacteria, Chlorophyll A, carotenoids, phycobilin pigments, fix N, produce stromatolites, origin of chloroplasts of red algae

iii. Chloroxybacteria , single genus, contain chlorophyll B, postulated source of chloroplasts in green algae and plants

iv. Actinomycetes - gram positive, filamentous growth form, nitrogen fixers, many antibiotics (streptomyocin like),

G. Bacteria and Evolution

1. Origins of metabolic diversity found in Monera

a. photosynthesis, glycolysis, oxidative phosphorylation all here first! 2. Rapid generation time perhaps the "key" to evolution of Prokaryotes

a. 1-3 hrs common for gen. time, but some every 20 min.

b. about 1 in 200 bacteria will have a mutation in DNA

c. billions of cells present in our popln, thus many mutants

d. Potential for rapid change in popln of bacteria characteristics

e. important in genetic diversity, ex., w/r antibiotic resistance

f. genetic recombination does occur as well

ex.'s, transfer of genes via viruses, plasmids, DNA fragments, conjugation

g. may be an alternative evolutionary strategy to sex