Announcements Exam 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. lacZ lacY lacA lacI P O Repressor: constitutively expressed. mRNA transcription translation Repressor protein binds operator preventing txn of lac. Repressor active, operon off.

Regulation of the lac Operon : Induction. Conditions: + lactose lacI lacZ lacY lacA P O Lactose is transported into the cell. allolactose = inducer. transcription mRNA translation Repressor protein allactose lacZ 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)] Activator Global 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 Repression: 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 Nitrate regulation system in E. coli.

The Dilemma of Bacteria Fighting Back "The emergence of bacteria with antibiotic resistance threatens to return us to the era before the development of antibiotics."

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”.