Effects of starvation on aggregate colonization and motility of marine bacteria

Abstract

Fluxes of particulate matter to depth and dynamics of dissolved organic matter in the water column are influenced by microbial processes associated with organic aggregates like marine snow. These microscale processes include the encounter between bacteria and aggregates, which has been previously modeled and tested with well-fed and actively growing bacteria. In the present study, we investigated the effects of starvation on initial bacterial colonization of aggregates by measuring colonization and detachment of 6 isolates in different physiological states (fed vs. starved) using model aggregates. Because aggregate encounter depends on motility, the motility behaviors of fed and starved bacteria of 3 selected strains were also compared using image analysis. All 6 fed isolates colonized faster and achieved significantly higher steady-state abundances on model aggregates than those that were starved. However, there was no difference in detachment rates between fed and starved bacteria. The 3 selected strains had significantly lower average swimming speeds when starved. Diffusivities calculated from motilities of 2 starved isolates were more than 6 times lower than those of their fed counterparts. Our results show that starvation significantly affects bacterial behavior and bacteria-aggregate interactions, which may lead to differences in particulate and dissolved organic matter fluxes and cycling under different productivity regimes.

Life under extreme energy limitation: a synthesis of laboratory- and field-based investigations

“…The energetic cost of motility is also influenced by the flagellar motor torque used by the cells (Li and Tang 2006), and the spatial extent of chemical gradients (micrometer to meter scale) (Mitchell 2002). Experiments with microbes from seawater, moreover, indicate lower average swimming speeds of starved compared to non-starved cells (Yam and Tang 2007), perhaps reflecting the higher energetic cost of fast compared to slow swimming.…”

Theory of island biogeography on a microscopic scale: organic aggregates as islands for aquatic pathogens

“…Alldredge 1979, Silver & Alldredge 1981, Alldredge & Cohen 1987, Lampitt et al 1993, Azam & Long 2001, environmental microbiology (e.g. Riley 1963, Caron et al 1986, Logan & Hunt 1987, Herndl 1988, Azam et al 1994, Kiørboe 2003, Grossart et al 2006, Yam & Tang 2007, the distribution of metals (e.g. Cowen & Silver 1984, Hebel et al 1986, phytoplankton ecology (Riebesell 1991, Kaltenböck & Herndl 1992, Kiørboe & Hansen 1993, Silver et al 1998, Thornton 2002, mesoplankton and benthic trophic interactions (e.g.…”