AnnouncementsExam 3: All material covered since exam 2 including: Fermentation & categories of microbes based upon

C and energy sources (Ch 4 & 6) Ch 7 Ch 8 (pp. 204-215: material covered in lecture) Selected material from Ch 21 (antibiotics).

Announcements

After Hours Passes- You must: Have a pass with your name listed. Have your student ID. Must have another Micro Student to accompany

you & he/she must have a pass. No one is permitted in the lab by themselves.

Call Security to let you into the Science building & into Room 203.

Regulation of the lac operon: Repression

Conditions: No lactose.

Repressor: constitutively

expressed.

lacZlacYlacAlacIP O

mRNA

transcription

translation

Repressor protein

binds operator preventing txn of lac.

Repressor active, operon off.

Regulation of the lac Operon : Induction.

Conditions: + lactose

Lactose is transported into the cell.allolactose = inducer.

lacZlacYlacAlacIP O

mRNA

transcription

translation

Repressor protein

allactoselacZ Y & A can be expressed.

Diauxic Growth Curve:

Lactose is present the entire time…… why is it not inducing the lac operon when glucose present?

Catabolite Repression: lac

operon

Key Players:Catabolite Activator Protein (CAP)- [cAMP

receptor protein (CRP)]

ActivatorGlobal regulator-

CAP activity is impacted by the level of glucose! HOW?

Glucose level indicator molecule:

Cyclic AMP (cAMP)- a signal to tell the cell how much glucose is present.

High glucose- decreased synthesis of cAMP; [cAMP]

Low glucose- increased synthesis of cAMP; [cAMP].

cAMP = inducer for CAP

Catabolite Repressio

n: lac operon

Fig. 7.19; p. 185

Alternative mechanisms for gene regulation:

Two Component Regulatory Systems:

A signal transduction mechanism used by bacteria to respond to external environmental factors.

Nitrate regulation system in E. coli.

Extracellular sensor domain

Intracellular transmitter domain- protein kinase

"The emergence of bacteria with antibiotic resistance threatens to return us to the era before

the development of antibiotics."

The Dilemma of Bacteria Fighting Back

How prevalent is antibiotic resistance?

Antibiotic resistance: example of genetic change & exchange!

Staphylococcus aureus & Enterococcus faecalis are primary culprits for Hospital acquired infections:

1988- Vancomycin Resistant Enterococcus recognized in US!

1997- Vancomycin resistance in MRSA documented in the US.

2002- VRSA reported to be completely resistant!

Is Antiobiotic resistance limited to Staphylococcus & Enterococcus?

Is Antiobiotic resistance limited to Staphylococcus & Enterococcus?

Table 12A from Talaro, Foundations in Microbiology.

Is antibiotic spread from one species to another limited to Staph &

Enterococcus?

Fig. 12.14 from Talaro, “Foundations in Microbiology”.

Is antibiotic spread from one species to another limited to Staph &

Enterococcus?

Fig. 12.14 from Talaro, “Foundations in Microbiology”.