Comparison of lysogeny (prophage induction) in heterotrophic bacterial and Synechococcus populations in the Gulf of Mexico and Mississippi river plume

Abstract

Lysogeny has been documented as a fundamental process occurring in natural marine communities of heterotrophic and autotrophic bacteria. Prophage induction has been observed to be prevalent during conditions of low host abundance, but factors controlling the process are poorly understood. A research cruise was undertaken to the Gulf of Mexico during July 2005 to explore environmental factors associated with lysogeny. Ambient physical and microbial parameters were measured and prophage induction experiments were performed in contrasting oligotrophic Gulf and eutrophic Mississippi plume areas. Three of 11 prophage induction experiments in heterotrophic bacteria (27%) demonstrated significant induction in response to Mitomycin C. In contrast, there was significant Synechococcus cyanophage induction in seven of nine experiments (77.8%). A strong negative correlation was observed between lysogeny and log-transformed activity measurements for both heterotrophic and autotrophic populations (r ¼ À0.876, P ¼ 0.002 and r ¼ À0.815, P ¼ 0.025, respectively), indicating that bacterioplankton with low host growth favor lysogeny. Multivariate statistical analyses indicated that ambient level of viral abundance and productivity were inversely related to heterotrophic prophage induction and both factors combined were most predictive of lysogeny (q ¼ 0.899, P ¼ 0.001). For Synechococcus, low ambient cyanophage abundance was most predictive of lysogeny (q ¼ 0.862, P ¼ 0.005). Abundance and productivity of heterotrophic bacteria was strongly inversely correlated with salinity, while Synechococcus was not. This indicated that heterotrophic bacterial populations were well adapted to the river plume environments, thus providing a possible explanation for differences in prevalence of lysogeny observed between the two populations.

Bacterial Growth and Mortality after Deposition of Saharan Dust and Mixed Aerosols in the Eastern Mediterranean Sea: A Mesocosm Experiment

“…An indirect confirmation that at T4 bacteria in A were more P-limited compared to SD could be the higher frequency of lysogenic cells, along with the particularly low bacterial production and growth rate. A negative relationship between bacterial production and the fraction of lysogenic cells has been found in natural and experimental conditions (Jiang and Paul, 1996;Long et al, 2008); it has been suggested that lysogeny is a prevalent viral life cycle under conditions that do not favor the growth of the hosts (Williamson et al, 2002;Weinbauer et al, 2003a). In our experiment, more lysogenic cells were measured in A compared to SD and the controls 4 days after deposition, suggesting that conditions were less favorable for the growth of the hosts at that time.…”

The genomic basis of trophic strategy in marine bacteria

“…It has previously been predicted that highly virulent lytic phages will take advantage of r-strategist hosts when they become transiently numerically abundant, whereas slowgrowing members of the community will be infected by less virulent and possibly nonlytic phages (20). Lysogeny has been shown to depend on host growth rate (21), and copiotrophic environments have been generally found to have a higher frequency of infected cells and phage causing larger lytic burst sizes compared with oligotrophic environments (22).…”

Grazing and viral lysis vary for different components of the microbial community across an estuarine gradient

“…This difference is probably due to variation in the proportion of grazers that are able to consume small cyanobacterial cells, or due to higher abundances of cyanobacteria within Mobile Bay in the summer. Although viruses infecting cyanobacteria are commonly found in marine waters (Suttle & Chan 1993, 1994, Long et al 2008), lysis of cyanobacteria was not detected. For peridinin, grazing was never detected; however, viral lysis may play a role in controlling the abundance and growth of this group.…”