Lytic replication of coliphage lambda in Salmonella typhosa hybrids

Area of Science:

• Microbiology
• Bacteriology
• Virology

Background:

• Bacteriophage lambda interactions with bacterial hosts are crucial for understanding gene transfer and viral replication.
• Escherichia coli K-12 and Salmonella typhosa exhibit distinct genetic mechanisms influencing phage susceptibility and replication.

Purpose of the Study:

• To investigate the genetic basis of lambda phage replication and host range in Salmonella typhosa hybrids.
• To identify specific Escherichia coli K-12 genetic elements required for lambda phage propagation in S. typhosa.

Main Methods:

• Construction of partially diploid Salmonella typhosa hybrids containing segments of the Escherichia coli K-12 chromosome.
• Lysogenization of hybrids with lambda phage, followed by induction and analysis of phage production.
• Transduction experiments to map the lambda attsite and assess phage DNA modification and restriction.
• Introduction of specific E. coli K-12 chromosomal regions via F-merogenotes to restore lambda replication.

Main Results:

• Salmonella typhosa hybrids with specific E. coli K-12 chromosomal segments (pro-ara-strA) supported lambda phage plaque formation and lysogeny.
• Loss of the K-12 replication region in S. typhosa hybrids abolished phage production, which could be restored by reintroducing the region.
• The lambda attsite in S. typhosa is located near the gal locus, similar to E. coli K-12.
• S. typhosa hybrids did not restrict lambda grown on E. coli K-12, and lambda propagated in S. typhosa was restricted by E. coli K-12, indicating a lack of K-12 DNA modification in S. typhosa.
• The E. coli K-12 genetic region from min 66 to 72 was identified as essential for lambda phage production in S. typhosa.

Conclusions:

• Specific Escherichia coli K-12 genes are necessary for the vegetative replication of lambda phage in Salmonella typhosa hybrids.
• The genetic map of E. coli provides a framework for understanding phage-host interactions across different bacterial species.
• Mutagenesis of lambda-insensitive S. typhosa hybrids can lead to altered phage sensitivity profiles.