Seasonal dynamics of marine snow‐associated and free‐living demethylating bacterial communities in the coastal northern Adriatic Sea

Abstract

Summary The extent of DMSP demethylation has been hypothesized to depend on DMSP availability and bacterial sulfur demand, which might lead to niche differentiation of the demethylating bacterial community. In this study, we determined DMSP concentrations in marine snow and the ambient water over a seasonal cycle and linked DMSP concentrations to the abundance of bacteria harbouring the demethylation dmdA gene in the Adriatic Sea. In marine snow, DMSP concentrations were up to four times higher than in the ambient water and three times higher in marine snow in summer than in winter. The average dmdA:recA gene ratio over the sampling period was 0.40 ± 0.24 in marine snow and 0.48 ± 0.21 in the ambient water. However, at the subclade level, differences in the demethylating bacterial community of marine snow and the ambient water were apparent. Seasonal patterns of potentially demethylating bacteria were best visible at the oligotype level. In the ambient water, the SAR116 and the OM60/NOR5 clade were composed of oligotypes that correlated to high DMSP concentrations, while oligotypes of the Rhodospirillales correlated to low DMSP concentrations. Our results revealed a pronounced seasonal variability and spatial heterogeneity in DMSP concentrations and the associated demethylating bacterial community.

Metagenomic Insights Into the Cycling of Dimethylsulfoniopropionate and Related Molecules in the Eastern China Marginal Seas

“…The potential to catabolize DMSP was abundant in all seawater and BYSS samples. DMSP demethylation appeared to be the dominant pathway in the seawater samples with dmdA predicted to be present in ∼40.0% of bacteria, which is consistent with the studies of Howard et al (2006Howard et al ( , 2008, Cui et al (2015), and Steiner et al (2019). Seawater bacteria with the potential to cleave DMSP were also abundant with dddP being the most abundant DMSP lyase gene (4.0-15.6%) but dddQ (6.0-14.1%) and dddK (8.3%) were also well represented.…”

Assessing Viral Abundance and Community Composition in Four Contrasting Regions of the Southern Ocean

“…Furthermore, viruses, phytoplankton, and prokaryotes are presumably key agents involved in making secondary metabolites, including volatiles that escape to the atmosphere and eventually may evolve into marine secondary aerosols, crucial in the creation of cloud condensation nuclei and, therefore, having consequent effects on climate [ 13 , 14 ]. A conspicuous secondary metabolite is dimethyl sulfoniopropionate (DMSP), an algal osmolyte that is produced in high intracellular concentrations by many phytoplankton taxa [ 15 , 16 , 17 ]. Two of the major aerosol-forming volatiles are isoprene (2-methyl-1,3-butadiene), which is a by-product of algal photosynthesis [ 14 , 18 ], and dimethyl sulfide (DMS), which derives from DMSP through the action of enzymatic lyase activity [ 15 , 16 , 19 , 20 ].…”

Functional Seasonality of Free-Living and Particle-Associated Prokaryotic Communities in the Coastal Adriatic Sea

“…Rhodobacterales ASV25 was enriched in the AW and MS-associated community (Figure 3). Vibrionales ASV24, ASV7 and Pirellulales ASV18 were enriched in MS and were previously reported as primarily MS-associated prokaryotes (Smith et al, 2013;Salazar et al, 2015;Steiner et al, 2019). The seasonal re-occurrence of Vibrio in the Adriatic and Mediterranean Sea has been linked to water stratification, elevated dissolved organic carbon concentrations and production of transparent exopolymeric particles (Zaccone et al, 2002;Tinta et al, 2015).…”

“…Marine snow (150 mL to 500 mL) and 1 L of ambient water were filtered onto 0.2 µm polyethersulfone filters (47 mm diameter, Supor, PALL Gelman) using an aspirator pump (Cole-Parmer). Filters were placed in cryovials (Biozym), flash-frozen in liquid nitrogen and stored at −80 • C. DNA was extracted using a standard phenol-chloroform method as described in Steiner et al (2019). Hereinafter, ambient water and marine snow are abbreviated as ambient water (AW) and marine snow (MS), respectively.…”