What is an Operon?

Cluster of genes cotranscribed from a common promoter.

 galactose + glucose=?

E. coli use the enzyme b-Galactosidase to cleave lactose into glucose and galactose.

They use the enzyme lactose permease to transport lactose across the membrane.

What do the E. coli Strains Lac⁺ , LacZ^-  LacY^-   and LacP do?

Lac⁺ - wild type, grows on lactose.

LacZ^- – mutant, does not grow on lactose.  no b-galactosidase.

Lactose Operon

lacZ: b-Galactosidase – cleaves lactose into glucose and galactose.

lacY: Lactose Permease – transports lactose through the membrane.

lacA: Thiogalactoside transacetylase.

What do the E. coli Strains LacY^-   and LacP and Lacl do?

LacY^- – mutant, does not grow on lactose.  no entry of lactose.

LacI^- –  mutant, never turns the system off. lac repressor.

 LacP^-– mutant, does not grow on lactose. no b-galactosidase or lactose entry.

The operon is negatively regulated by a repressor that dissociates when the inducer ligand binds to it.

E. coli Strains

Lac⁺ - wild type, grows on lactose.

LacZ^- – mutant, no b-galactosidase.

LacY^- – mutant, no entry of lactose.

LacP^- – mutant, no transcription.

LacI^- –  constitutive mutant, lac repressor.

O^c – constitutive mutant, operator.

LacI and LacZYA are transcribed separately.

LacI and LacZYA are transcribed separately.

Normally, the LacI repressor binds to the LacO operator.  This prevents transcription.

What is Complementation?

Addition of a wild-type gene to restore the function to a loss-of-function mutant.

Performed in E. coli with F’ plasmids. F’ plasmids have all the features of an F Factor plasmid, along with some of the bacterial DNA.

You can ‘cross’ mutants to bacteria with an F’ plasmid with the wild-type gene.

Lac⁺   + F’lac⁺ = still grows on lactose.

LacZ^- + F’lac⁺ = now grows on lactose.

LacY^- + F’lac⁺ = now grows on lactose.

LacP^- + F’lac⁺ = now grows on lactose.

LacI^-  + F’lac⁺ = makes enzymes normally.

   O^c   + F’lac⁺ = makes excess enzymes.

Lac^- – enzymes are never made and it cannot survive on lactose.

 Lac⁺ – enzymes made when needed and can survive on lactose.

 Lac⁺⁺ – enzymes are made constitutively and it can survive on lactose.

What is catabolite repression?

E. coli will preferentially consume glucose, instead of lactose.Glucose acts as an inhibitor of the lac operon. It also inhibits the metabolism of other sugars. Glucose controls a positive regulator, called catabolite activator protein.

Activates the lac and other sugar operons when glucose is low. It binds to a sequence in front of the promoter, and helps RNA polymerase bind. It can increase the rate of transcription by up to fifty times. Removing the repressor increases the rate by up to ten times.

What is the Biological Species Concept?

Based on reproductive isolation. A species is a group of organisms that can mate and produce fertile offspring

1)    Ring Species – some populations can breed with two nearby populations, but those two populations cannot breed.

2)    Asexually Reproducing Organisms – microbes cannot be classified by the biological species concept.

 What are different ways to conduct Morphology Classification?

Bacterial Shape (bacillus vs coccus, ect)

Colony Color

Colony Shape

Colony Texture

How does Biochemical and Physiological classification work?

1)    Cell Wall Structures (gram stain)

2)    Surface Structures (O-antigen)

3)    Enzymes (catalase test)

4)    Metabolism (mannitol salt agar)

1)    Morphology

2)    Biochemistry and Physiology

3)    Environment

4)    Ecological Niche

5)    Disease Caused (pathogens only).

Domain, Kingdom, Phylum, Class, Order, Family, Genus ,Species

What is Pseudopeptidoglycan?

NAM is replaced with a different sugar.

Sugars are linked at the 1-3 carbon and not the 1-4 carbon (lysozyme resistant).

Uses normal amino acids for the peptide side chains (penicillin resistant

1)    Bacillus and Coccus Structure

2)    Genome Size

3)    Nucleoid

4)    Operons

What are Achaea similarities to eukaryotes?

1)    Introns

2)    Polymerase Structure

3)    Ribosome Structure

4)    Histones

What are some facts about Sulfur Metabolizers?

Anaerobic and live at high temperatures.

Difficult to culture and study

Sulfur for an electron acceptor or donor.

Have G-C rich DNA and a reverse gyrase that supercoils their DNA.

Includes the Thermoproteus, Sulfolobus, and Pyrolobus genera.

What does Pyrolobus fumarii do?

Lives in deep-sea iron sulfide vents.

Grows at 113^o C.

Can survive for an hour in the autoclave.

Chemolithotroph – oxidizes H₂.

What do Methanogens do?

Generate methane, usually by metabolizing carbon dioxide.

Cannot live in oxygen environments.

Produce methane in the rumen of the cow.

Obtain carbon from CO₂ and use the reverse reaction of the citric acid cycle to make citrate.

What are some facts about Haloarchaea?

Grow in 1.5 M to 4.3 M NaCl.

Most have bacterioruberin (red pigment).

Maintain a KCl concentration of 4 M.

Have acidic proteins and G-C rich DNA.

Use sodium-motive force to rotate flagella, instead of proton-motive force.

Have a normal temperature range.

Easy to study and culture.

What are Halobacterium salinarium called? What can they do?

They are considered extreme halophiles. They can do photosynthesis without chlorophyll.They

uses the pigment bacteriorhodopsin.

share similarities to archaea.

Aquifex – grows at up to 95^o C.  Some metabolize sulfur or hydrogen.

Some have ether-linked membrane lipids.

Can be gram-negative or gram-positive.

Some have photosystem II, and can perform photosynthesis.

Includes the Deinococcus genus.

It is a Deep-Branching Thermophile that:

-Consists of forty-two species.

-Gram positive cocci.

-Grow very slowly.

Resistant to desiccation, low temperatures, vacuum, low pH, and radiation.

Can survive 5000 Gray without problems.(ionizing radiation)

15,000 Gray will kill about a third.

Fortunately, nonpathogenic. Can be killed by heating to 42^oC.

Has multiple chromosomes arranged in a ring structure.

Repairs double strand breaks caused by ionizing radiation with homologous recombination.

Genome sequenced in 1999.

Transgenic strains used to detoxify ionic mercury in nuclear waste.

Small photosynthetic rods.

Have photosystems I and II.

Formerly called blue-green algae.

Some can form heterocysts to fix nitrogen from the environment.

These cells can no longer perform photosynthesis.

What are Chlamydiae? What is a specific speices?

Parasitic, infects eukaryotic cells.

Chlamydia trachomatis

Nonmotile cocci.

No peptidoglycan.

Elementary bodies will crosslink the outer membrane with proteins.

Imports ATP from the host cell.

Most common bacterial venereal disease

Symptoms of Chlamydia trachomatis in males?

Symptoms in Males

Sometimes asymptomatic.

Burning urination.

Painful discharge.

Similar to Gonorrhea.

Symptoms of Chlamydia trachomatis  in Females?

Sterility due to fallopian tube damage.

Can infect infants during birth.

Gram-negative helical rods (flexible).

Axial Filament – flagella located in the periplasm and along the entire bacterium.

Propels the cell with a spiral motion.

Very difficult to culture.

A few species are pathogenic.

What type of bacteria is a Borrelia burgdorferei?

It is a Spirochete.

It Causes Lyme disease.

Its transmitted by deer ticks.

Causes Flu-like symptoms followed by joint pain and neurological problems.

Can be treated with antibiotics, if it is caught early.

What is Syphilis?(bacteria type)

What are the stages?

It is a Spirochetes.

Stages of Syphilis

Primary – chancre appears after several weeks.

Secondary – a rash can appear months later.

Tertiary – tissues can develop granulomas years later, can cause brain damage.

Syphilis can be treated with penicillin if caught early.

Proteobacteria Facts?

Named for the fact that they share so little in common.

All are gram-negative.

All have lipopolysaccharide on the outer membrane.

Includes E. coli and Salmonella.

What are Alpha Proteobacteria? Some examples?

Also a large distribution of anaerobic rods.

Alpha Proteobacteria Examples

1)     Caulobacter crescentus

2)     Rhizobium

3)     Rickettsia rickettsii

What do Rickettsia rickettsii cause?Transmitted? Infect what?

-Causes Rocky Mountain spotted fever.

Transmitted by the wood tick.

Infect endothelial cells by inducing phagocytosis of the bacteria.

Consume citric acid cycle intermediates.

Symptoms of rocky mountain spotted fever?

Initial symptoms are similar to a flu.

A rash will usually also develop.

Sometimes fatal, but it can be treated.

Many acquire carbon from decaying organic material.

Two Important Pathogens

1)     Neisseria meningitides – one cause of bacterial meningitis.

2)     Neisseria gonorrhoeae – cause of the sexually transmitted disease gonorrhea.

Gamma Proteobacteria

Largest of the five groups.

Rods – straight or slightly curved.

Gamma Proteobacteria Examples

1)     Purple sulfur bacteria - use H₂S as an electron source. 2)     Pseudomonas

3)     Enterobacteriaceae – includes E. coli, Salmonella, Shigella, and Yersinia pestis.

They are Gamma Proteobacteria.

-Opportunistic pathogen.

-Can infect the immune-compromised.

-Major cause of death in burn victims.

Frequently are curved rods.

Two Important Genera

1)     Myxobacteria – live in the soil.

Bdellovibrios – parasitize other bacteria

Myxococcus xanthus is a Delta Proteobacteria.

Have no flagella, but can move on soil.

When nutrients are low, they form a fruiting body.

The fruiting body contains myxospores, which are released into the wind.

Bdellovibrios bacteriovorus  is a Delta Proteobacteria.

-Infect and parasitize other gram negatives.

-Invades the periplasm and reproduces.

-Epsilon Proteobacteria

-Smallest of the five groups.

Helicobacter pylori

-Causes stomach ulcers.

-Colonizes the epithelium of the stomach