LATERAL GENE TRANSFER 1. (A) Why are mutations not typically as beneficial as lateral gene transfer for the evolution of bacterial species? (B) What is the effect that lateral gene transfer has on the evolution of bacteria?

A) Mutations are not typically beneficial as lateral gene transfer because it often disrupts or destroys the function of a gene, whereas lateral gene transfer is a way to add functions to the recipient cell (this can be a valuable new function).

B) Lateral gene transfer is a quicker way for a population to generate versatility and diversity. Bacterial species that have greater diversity have a higher chance of adapting to changing environments, and thus surviving. Moreover, lateral gene transfer plays an important role in adaptation and evolution in bacterial species because it can add an important function for survival, such as antibiotic resistance or virulence factors.

2. (A) What are three examples of bacterial genes or plasmids that are known to have been laterally transferred among bacteria? What new traits did they give the recipients? (B) In what bacteria (give full genus and species name) have they been found? (C) If known, who transferred the genes to whom? [3 points of extra credit will be given if at least one of your 3 choices is from the recent studies mentioned in class.] A) The R100 plasmid found in Escherichia, Klebsiella, Salmonella (enterics) has given genes for resistance to sulfonamides, streptomycin, tetracycline, and mercury. A penicillinase-­‐producing plasmid from Streptococcus may have been laterally transferred to Neisseria. E. coli O157:H7 has a Shigella plasmid, which allows it to produce the shiga toxin.

The marine bacterium Zobellia galactanivorans transferred its genes to the Japanese gut bacterium Bacteroides plebeius, giving it the ability to break down carbohydrates of marine algae.

These genes gives this gut bacterium the ability to break down the complex carbohydrates of marine algae, allowing Japanese people to digest molecules that they could not normally break down.

3. If a fragment of a chromosome is transferred, describe what must happen inside the recipient cell in order for the transfer to work. Integration or recombination needs to occur in the recipient cell in order for the transfer to work. Any DNA that is not integrated into the chromosome will be degraded (DNA does not function in the cytoplasm).

4. Why are plasmids a convenient way for bacteria to transfer DNA?

A plasmid is an independent, circular, self-­‐replicating DNA molecule that carries only a few genes. Because they are small and can function independently of the chromosome,