Prophage induction of indigenous marine lysogenic bacteria by environmental pollutants
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MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 164:125-133 (1998) - doi:10.3354/meps164125 Prophage induction of indigenous marine lysogenic bacteria by environmental pollutants Pamela K. Cochran, Christina A. Kellogg, John H. Paul* Department of Marine Science, University of South Florida, 140 7th Ave. South, St. Petersburg, Florida 33701, USA *Addressee for correspondence. E-mail: jpaul@seas.marine.usf.edu Lysogenic bacteria may be abundant components of bacterial assemblages in marine waters. The tremendous number of viruses found in estuarine and other eutrophic environments may be the result in part of induction of prophages. Mitomycin C is the inducing agent of choice for prophage induction; however this is not naturally found in the marine environment. We determined the capability of environmentally important pollutants to effect prophage induction in natural populations of marine bacteria. We investigated Aroclor 1248, a PCB mixture, bunker C fuel oil #6, and a pesticide mixture as inducing agents for natural bacterial communities from the Gulf of Mexico. Mitomycin C was also employed as a positive control for induction. Induction was determined as a significant increase in viral direct counts compared to control and ranged from 149 to 1336% of the controls. Two-thirds of the environments sampled showed prophage induction by one of the methods utilized, with the PCB mixture and Aroclor 1248 giving the highest percent efficiency (75%) of induction. This study shows that many environmentally important pollutants may be inducing agents for natural lysogenic viral production in the marine environment. Marine bacteriophage · Lysogeny · Gulf of Mexico · Pollution Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 164. Publication date: April 09, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.Keywords:
Prophage
Lysogenic cycle
Marine bacteriophage
ABSTRACT 1) Hydroxyurea, a reversible DNA synthesis inhibitor, was used to study the mechanism of prophage λ induction in Escherichia coli K12. Induction of prophage was judged on two criteria: increase of phage‐producing cells and loss of colony‐forming ability of the cells. 2) Hydroxyurea induced an increase of phage‐producing cells only in lysogenic strains known to be inducible with ultraviolet irradiation for prophage development and not in strains such as E. coli K12 (λ ind – ) or E. coli K12 rec A (λ + ). 3) When protein synthesis was inhibited, hydroxyurea did not increase phage‐producing cells of lysogenic strains; it showed a bacteriocidal effect on lysogenic rec A + strains, but not on nonlysogenic strains. 4) The sensitivity of E. coli K12 rec A to hydroxyurea was independent of whether or not the cells were lysogenic. 5) From the results it is suggested that certain steps leading to loss of colony‐forming ability (i.e. prophage induction) do not require de novo protein synthesis but require the presence of the host rec A + gene.
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Prophage
Lysogenic cycle
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Temperateness
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Escherichia coli K12 strains lysogenic for Mu gem2ts with the prophage inserted in a target gene (i.e., lacZ::Mu gem2ts lysogenic strains) revert to Lac+ by prophage precise excision with a relatively high frequency (about 1×10−6). The revertants obtained are still lysogens with the prophage inserted elsewhere in the bacterial chromosome. We have observed that, with the time of storage in stabs, bacterial cultures lysogenic for Mu gem2ts lose the ability to excise the prophage. The mutation responsible for this effect was co-transducible with the gyrB gene. After the removal of the prophage by P1 vir transduction from these strains, one randomly chosen clone, R3538, was further analyzed. It shows an increment of DNA supercoiling of plasmid pAT153, used as a reporter, and a reduced β-galactosidase activity. On the other hand, R3538 is totally permissive to both lytic and lysogenic cycles of bacteriophage Mu.
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Level of competence reached by Bacillus subtilis 168 lysogenic for temperate phage φ 105 was reduced compared to that reached by nonlysogenic cells. This effect was probably related to an alteration of the bacterial surface. Deoxyribonucleic acid extracted from φ 105 lysogenic bacteria was used to transform other lysogenic bacteria. About 25% linkage was found between the bacterial phe-1 marker and prophage marker ts N15. The order of a few prophage markers relative to phe-1 was established in three-factor crosses. The usefulness of this system for a study of the linkage between an integrated prophage genome and that of its host was discussed.
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Abstract Lysogeny is the harbouring of a dormant bacteriophage (phage) genome in a growing bacterial host. The well‐studied coliphage lambda system provided the paradigm for the role of regulatory proteins in determining the fate of the infected cell (lysis vs lysogeny) as well as the role of environmental signals that influence this decision. Studies of lambda also led to the classic models for site‐specific integration of phage DNA into the bacterial chromosome and for prophage induction during the SOS response by RecA‐mediated repressor cleavage. Beyond a common requirement for a phage‐encoded repressor to maintain lysogeny, phages other than lambda exhibit substantial diversity in the mechanisms underlying regulation of the lysis/lysogeny decision, integration, and prophage induction. Lysogeny has profound consequences on bacterial evolution, leading to acquisition of new traits, enhanced bacterial fitness, gene disruption and/or genomic rearrangements. Phages that are capable of lysogeny provide a reservoir of genetic diversity for their hosts. Key Concepts Lysogeny is widespread; prophages are present in ∼1/2 of all sequenced bacterial chromosomes, and many strains carry multiple prophages. Regulation of the phage lysis/lysogeny decision is an example of a bistable gene expression circuit. DNA looping occurs when protein molecules which bind to noncontiguous DNA sites also bind to each other, bringing together DNA sites that are normally some distance apart. Some temperate phages can perpetuate their genomes without integration into the chromosome by plasmid formation, where phage genomes replicate autonomously to keep pace with cell division. Prophage induction is the activation of a prophage to enter the lytic cycle, either spontaneously or by treating lysogenic cells with various agents. Specialised recombination protein machineries are required to establish phage integration. These can be host or phage encoded and bind to dsDNA sequences to catalyse recombination. Site‐specific recombination, which entails breakage and joining of DNA at specific sequences, is used by phages and plasmids and facilitates separation of daughter chromosomes in bacterial cell division. In transposition, some DNA elements, including phage genomes, move from one site to another by action of transposases encoded by the element. Temperate phages provide a mobile genetic reservoir that allows bacteria to adapt to new environments. Prophage‐encoded accessory genes provide new traits that can enhance bacterial fitness or virulence. Lysogeny is transient, allowing bacteria plasticity in their responses to environmental challenges.
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Lytic cycle
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