Chemotaxis of Silicibacter sp. Strain TM1040 toward Dinoflagellate Products

Abstract

The ␣-proteobacteria phylogenetically related to the Roseobacter clade are predominantly responsible for the degradation of organosulfur compounds, including the algal osmolyte dimethylsulfoniopropionate (DMSP). Silicibacter sp. strain TM1040, isolated from a DMSP-producing Pfiesteria piscicida dinoflagellate culture, degrades DMSP, producing 3-methylmercaptopropionate. TM1040 possesses three lophotrichous flagella and is highly motile, leading to a hypothesis that TM1040 interacts with P. piscicida through a chemotactic response to compounds produced by its dinoflagellate host. A combination of a rapid chemotaxis screening assay and a quantitative capillary assay were used to measure chemotaxis of TM1040. These bacteria are highly attracted to dinoflagellate homogenates; however, the response decreases when homogenates are preheated to 80°C. To help identify the essential attractant molecules within the homogenates, a series of pure compounds were tested for their ability to serve as attractants. The results show that TM1040 is strongly attracted to amino acids and DMSP metabolites, while being only mildly responsive to sugars and the tricarboxylic acid cycle intermediates. Adding pure DMSP, methionine, or valine to the chemotaxis buffer resulted in a decreased response to the homogenates, indicating that exogenous addition of these chemicals blocks chemotaxis and suggesting that DMSP and amino acids are essential attractant molecules in the dinoflagellate homogenates. The implication of Silicibacter sp. strain TM1040 chemotaxis in establishing and maintaining its interaction with P. piscicida is discussed.

Chemotaxis by natural populations of coral reef bacteria

“…(Keller et al, 1989;Broadbent et al, 2002) and the coral animal (Raina et al, 2013) have the capacity to produce significant quantities of DMSP. Our results confirm that, similar to other marine microorganisms (Miller et al, 2004;Seymour et al, 2010;Sharp et al, 2012), coralreef-associated bacteria use chemotaxis to enhance their access to DMSP or to follow DMSP gradients as a cue to locate the host (Garren et al, 2014). The dominant bacterial taxa responding to DMSP included known coral-associated species that have the capacity to degrade DMSP (Flavobacteriaceae) and DMS (Comamonadaceae) or both (Rhodobacteracea, Pseudomonaceae and Halomonaceae) (Raina et al, 2010).…”

Patterns and mechanisms of genetic and phenotypic differentiation in marine microbes

“…In the planktonic lifestyle, these organisms probably grow in bursts, which are locally quickly erased by predation so that overall they should have higher turnover rates than other bacterioplankton (Mourino-Perez et al 2003;Worden et al 2006). There are strong indications that both Vibrio and Roseobacter sense and respond to their surroundings by several mechanisms, including: quorum-sensing systems (Gram et al 2002;Moran et al 2004); production of antibacterial compounds (Bruhn et al 2005); chemotaxis (Miller et al 2004;McCarter 2006); association with animal or algal cells (Buchan et al 2005); and rapid surface colonization (Dang & Lovell 2000;Thompson & Polz 2006).…”

Variability in Microbial Community Composition and Function Between Different Niches Within a Coral Reef

“…The chemical products released from corals and algal exudates are often strong chemoattractants for motile marine bacteria [67,[93][94][95]. Coral mucus and the exudates of Symbiodinium are rich in several organic compounds including amino acids, sugars and DMSP [6,63,64,[68][69][70], which are known chemoattractants for marine bacteria [7,53,96], and have recently been shown to attract key coral pathogens [95]. Microscale gradients in these compounds in the microenvironment immediately adjacent to the coral surface may promote chemotactic migration of bacterioplankton cells to the coral holobiont [95].…”