Project description:Optimality of the spontaneous prophage induction rate. Cortes MG1, Krog J2, Balázsi G3. 1 Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA. 2 The Louis and Beatrice Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA. 3 Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794, USA. Electronic address: gabor.balazsi@stonybrook.edu. Abstract Lysogens are bacterial cells that have survived after genomically incorporating the DNA of temperate bacteriophages infecting them. If an infection results in lysogeny, the lysogen continues to grow and divide normally, seemingly unaffected by the integrated viral genome known as a prophage. However, the prophage can still have an impact on the host's phenotype and overall fitness in certain environments. Additionally, the prophage within the lysogen can activate the lytic pathway via spontaneous prophage induction (SPI), killing the lysogen and releasing new progeny phages. These new phages can then lyse or lysogenize other susceptible nonlysogens, thereby impacting the competition between lysogens and nonlysogens. In a scenario with differing growth rates, it is not clear whether SPI would be beneficial or detrimental to the lysogens since it kills the host cell but also attacks nonlysogenic competitors, either lysing or lysogenizing them. Here we study the evolutionary dynamics of a mixture of lysogens and nonlysogens and derive general conditions on SPI rates for lysogens to displace nonlysogens. We show that there exists an optimal SPI rate for bacteriophage λ and explain why it is so low. We also investigate the impact of stochasticity and conclude that even at low cell numbers SPI can still provide an advantage to the lysogens. These results corroborate recent experimental studies showing that lower SPI rates are advantageous for phage-phage competition, and establish theoretical bounds on the SPI rate in terms of ecological and environmental variables associated with lysogens having a competitive advantage over their nonlysogenic counterparts. Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Project description:Temperate bacteriophages (prophages) have recently been demonstrated in Campylobacter jejuni. However, what they do there is largely unknown. In the series of studies that are the subject of these submissions we have investigated the relative expression levels of proteins in C. jejuni isolates that differ in the presence or absence of the CJIE1 prophage. At the time of the initial investigations whole genome sequence data were not available for the isolates used, though DNA microarray data indicated that the isolates were very closely related. The overall project was carried out through four separate experiments. The first set of experiments (experiment 1) therefore compared protein expression in 4-plex iTRAQ experiments using three isolates carrying the (previously sequenced) prophage with a fourth isolate that was epidemiologically and genetically related to these isolates but which naturally lacked the CJIE1 prophage. Three replicate experiments were done. These isolates were grown on medium containing blood to obtain optimal growth and determine whether any differences were found. Three replicate experiments were done. However, since these growth conditions may not mimic in vivo growth of the organism the results may not be considered relevant or very interesting. Previous work in the scientific literature indicated that growth on medium lacking blood but containing sodium deoxycholate induced the expression of at least some proteins associated with virulence and provided data thought to be of relevance to the virulence of the bacterium. Therefore two isolates were chosen, one with and one without the CJIE1 prophage. Each of three replicates of a 4-plex iTRAQ experiment compared protein expression of the two isolates (00-2425 and 00-2426) after growth on Mueller-Hinton agar with and without 0.1% sodium deoxycholate. There was pretty good overlap between the proteins expressed in the first two experiments but, because all results were expressed as log2 change values, it was difficult to determine whether the expression of some proteins was completely absent in one or the other isolate. As well, protein expression overall showed quite extensive differences compared with the first experiment that we attributed to the lack of blood in the growth medium; we thought we might be seeing a response to limited iron as well. Finally, the response to the deoxycholate was extensive, and we wished to further explore this phenomenon as a means of determining or verifying what effects were due to the presence of the CJIE1 prophage and which were due to other differences. Further 4-plex iTRAQ experiments compared protein expression for each of isolate after growth on medium containing blood, without blood, without blood plus sodium deoxycholate, and without blood plus 2.5% Oxgall. Comparison of the results for isolate 00-2425 (with the CJIE1 prophage) and 00-2426 (without the prophage) identified a small number of proteins that could not be detected in one or the other isolate and allowed discrimination of the effects of the prophage from the responses to iron limitation and bile salt preparations. This dataset is associated with the first experiment, experiment 1, which compares C. jejuni isolates carrying the CJIE1 prophage (00-2425, 00-2538, 00-2544) with a very closely related isolate lacking the prophage (00-2426)

Project description:Temperate bacteriophages (prophages) have recently been demonstrated in Campylobacter jejuni. However, what they do there is largely unknown. In the series of studies that are the subject of these submissions we have investigated the relative expression levels of proteins in C. jejuni isolates that differ in the presence or absence of the CJIE1 prophage. At the time of the initial investigations whole genome sequence data were not available for the isolates used, though DNA microarray data indicated that the isolates were very closely related. The overall project was carried out through four separate experiments. Previous work in the scientific literature indicated that growth on medium lacking blood but containing sodium deoxycholate induced the expression of at least some proteins associated with virulence and provided data thought to be of relevance to the virulence of the bacterium. The second set of experiments (experiment 2) compared protein expression in 4-plex iTRAQ experiments using two isolates grown on medium with and without 0.1% sodium deoxycholate to further explore the effects of the CJIE1 prophage, if any, on protein expression. Results from that experiment indicated that there was an unexpectedly large bile response, and that there were differences in expression from the first experiment that may be attributable to the presence of blood in the culture medium in the first experiment, compared with the use of medium without blood in the second experiment. Experiment 3 was therefore designed to compare protein expression of the CJIE1-carrying isolate 00-2425 after growth on medium containing blood, without blood, and without blood but with bile salts. In experiment 4 we grew isolate 00-2426, which lacks prophage CJIE1, on the same four media. The goals were to determine if the differences in protein expression (detection) were similar to those in isolate 00-2425 and if there were any differences that could be attributed to the presence or absence of the CJIE1 prophage.

			Action	DRS
		Other
	SRR28794226_1.fastq.gz	Fastqsanger.gz
	SRR28794226_2.fastq.gz	Fastqsanger.gz
	SRR28863353_1.fastq.gz	Fastqsanger.gz
	SRR28863353_2.fastq.gz	Fastqsanger.gz

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