Lecture 45

Question 1

Bacteria typically contain _____ along with their double stranded circular DNA (chromosomes are condensed into ______). These ______ are autonomously replicating circular DNA molecules that confer antibiotic resistance and are the source of toxin production.

Answer 1

Plasmids

Supercoils

Plasmids

Question 2

Many antibiotics target the peptidoglycan cross-linkage. While Gram ____ bacteria are not very diverse in this linkage, Gram ____ are. This will affect the sensitivity of the bacteria to certain antibiotics. Both _____ and _____ are antibiotics that block the transpeptidation reaction required for cross-linking.

Answer 2

Gram -

Gram +

Penicillin

Vancomycin

Question 3

Some bacteria can grow in the presence of antibiotics that inhibit cell wall synthesis; they grow without a cell wall. These are called __-forms (“Protoplasts” for Gram ___/”Spheroplasts” for Gram ___), and can be seen sometimes in chronic infections. What would happen to these cells in low vs high osmotic pressure environments?

Answer 3

L-forms

Gram +

Gram -

In low osmotic pressure –> they swell and lyse. In high –> they can survive.

Question 4

Some species of bacteria, including Clostridium and Bacillus, can alter their life cycles in times of low resources. They form ____, from which almost all the water has been removed, leaving behind some DNA, ribosomes, and heat-resistant Ca-_______ acid.

Answer 4

Spores

Ca-dipicolinic acid

Question 5

Most bacteria are Heterotrophic, meaning they require a reduced ____ source for energy, sulfate, phosphate, and reduced _____ (a source of NH3 for amino acid synth).

Answer 5

Carbon

Ammonia

Question 6

Bacteria can be cultured on different media. If the exact contents and their amounts used in the medium are known, it is considered ______. If the contents are not measured, and something like yeast extract is used, this medium is considered _________. Some bacteria MUST be cultured with with cells (i.e. ______ found in armadillos or T. pallidum - causes syphilis - grown in rabbit testicles.)

Answer 6

Defined

Undefined

M. leprae

Question 7

Bacterial metabolism is diverse, and this can be used diagnostically. For example, N. meningitidis can grow in the presence of ______ alone, while N. gonorrhea requires _____. _____ strips are used to identify differences in bacterial metabolism.

Answer 7

Maltose

Glucose

API strips

Question 8

The growth cycle of bacteria occurs in four stages: Lag, Log, Stationary, and Death. During which of these stages are bacteria LEAST susceptible to some cell wall antibiotics, and why might that be?

Answer 8

During the Lag and Stationary phase, and probably during the Death phase, because these types of antibiotics require the bacteria to be in a growth phase in order to work.