Community-Level and Species-Specific Associations between Phytoplankton and Particle-Associated Vibrio Species in Delaware's Inland Bays

Abstract

Vibrio species are an abundant and diverse group of bacteria that form associations with phytoplankton. Correlations between Vibrio and phytoplankton abundance have been noted, suggesting that growth is enhanced during algal blooms or that association with phytoplankton provides a refuge from predation. Here, we investigated relationships between particle-associated Vibrio spp. and phytoplankton in Delaware's inland bays (DIB). The relative abundances of particle-associated Vibrio spp. and algal classes that form blooms in DIB (dinoflagellates, diatoms, and raphidophytes) were determined using quantitative PCR. The results demonstrated a significant correlation between particle-associated Vibrio abundance and phytoplankton, with higher correlations to diatoms and raphidophytes than to dinoflagellates. Species-specific associations were examined during a mixed bloom of Heterosigma akashiwo and Fibrocapsa japonica (Raphidophyceae) and indicated a significant positive correlation for particle-associated Vibrio abundance with H. akashiwo but a negative correlation with F. japonica. Changes in Vibrio assemblages during the bloom were evaluated using automated ribosomal intergenic spacer analysis (ARISA), which revealed significant differences between each size fraction but no significant change in Vibrio assemblages over the course of the bloom. Microzooplankton grazing experiments showed that losses of particle-associated Vibrio spp. may be offset by increased growth in the Vibrio population. Moreover, analysis of Vibrio assemblages by ARISA also indicated an increase in the relative abundance for specific members of the Vibrio community despite higher grazing pressure on the particle-associated population as a whole. The results of this investigation demonstrate links between phytoplankton and Vibrio that may lead to predictions of potential health risks and inform future management practices in this region. Bacteria within the genus Vibrio are naturally abundant in marine and estuarine environments (1), where they exhibit two alternative growth strategies: (i) association with particles as a biofilm or (ii) as free-living bacterioplankton (2). Association with planktonic organisms plays an important role in the ecology of Vibrio (3) by providing an enriched microenvironment for Vibrio spp. (4-6). Previous research demonstrated that planktonic copepods, in particular, enhance the survival and distribution of Vibrio in temperate and tropical areas (7,8). Associations with plankton may also provide a refuge from grazing by bacterivorous protozoa (9, 10), which can be substantial in some areas (11). Matz et al. (9), for example, showed that the cell density of Vibrio cholerae within a biofilm remained stable in the presence of protozoa, whereas planktonic cells were rapidly eliminated. However, particle association may not always be advantageous, as it may subject the cells to sinking forces or losses through "collateral damage" when host cells are preyed upon (10).In addition to copepods, Vibrio spp. also form attach...

Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic

“…The sharp increase in Vibrio abundance observed in recent years (e.g., 2000 onward) is concomitant with an increase of certain phytoplankton species, notably diatoms (e.g., Thalassiosira spp., Rhizosolenia imbricata), and a decline in abundance of other species, especially dinoflagellates (e.g., mainly Ceratium species). These results agree with recent work that demonstrated a significant correlation between Vibrio abundance in seawater and phytoplankton, with higher correlations with diatoms compared with dinoflagellates (48). One possible explanation for this finding is that diatoms genera, such as Thalassiosira, use chitin as a structural component of the silica cell wall, and it has been recently shown that some Vibrio species interact with diatom-derived chitin to foster their environmental persistence (42).…”

Variability of planktonic and epiphytic vibrios in a coastal environment affected by <em>Ostreopsis</em> blooms

“…Quantitative and qualitative differences in phytoplankton species composition may lead to pronounced differences in bacterioplankton species composition (Pinhassi et al 2004). In particular, the relationship between vibrios and specific groups of phytoplankton is controversial, and some authors suggest a preferential association with dinoflagellates (Eiler et al 2006), while others suggest a minor link between the two groups (Main et al 2015). Our data show a positive relation between the abundances of vibrios and of the dinoflagellate Ostreopsis at Llavaneres.…”

“…Vibrios have been detected on a large variety of biological surfaces, especially animals (Thompson et al 2004, Baffone et al 2006, Main et al 2015, and are also associated with various types of organic particles of non-animal origin (Lyons et al 2007, Froelich et al 2013. Recently, there has been evidence that vibrios can remain free-living (Mourino-Perez et al 2003, Worden et al 2006, Eiler et al 2006, although little is known on the factors determining whether they remain free-living versus particle-attached (Takemura et al 2014).…”

Indole signalling and (micro)algal auxins decrease the virulence of Vibrio campbellii, a major pathogen of aquatic organisms

“…Vibrios, including those belonging to the Harveyi clade, are known to be able to associate with (micro)algae (Nealson and Hastings, 2006;Manset et al, 2013;Main et al, 2015), which (like terrestrial plants) are known to produce various indole analogues as auxin hormones (Stirk et al, 2013;Lu and Xu, 2015). Auxins have been reported to affect various phenotypes in terrestrial bacteria (Spaepen and Vanderleyden, 2011).…”