Dynamics of extracellular polymeric substance (EPS) production and loss in an estuarine, diatom-dominated, microalgal biofilm over a tidal emersio-immersion period

Abstract

We studied patterns of production and loss of four different extracellular polymeric substance (EPS) fractionscolloidal carbohydrates, colloidal EPS (cEPS), hot water (HW)-extracted and hot bicarbonate (HB)-extracted fractions-and community profiles of active (RNA) bacterial communities by use of Terminal-Restriction Fragment Length Polymorphism (T-RFLP) analysis of reverse transcription-polymerase chain reaction amplified 16S rRNA in mudflats in the Colne Estuary, United Kingdom, over two tidal emersion-immersion cycles. Colloidal carbohydrates and intracellular storage carbohydrate (HW) increased during tidal emersion and declined during tidal cover. The dynamics of cEPS and uronic acid content were closely coupled, as were the HB fraction and HB uronic acids. Changes in monosaccharide profiles of HW and HB fractions occurred during the diel period, with some similarity between cEPS and HB fractions. Increasing enzymatic release rates of reducing sugars and increased reducing sugar content were correlated with increased concentrations of colloidal carbohydrate and cEPS during the illuminated emersion period, and with the amount of HB-extracted uronic acids (the most refractory EPS fraction measured). Loss of reducing sugars was high, with sediment concentrations far below those predicted by the measured in situ release rates. T-RFLP analysis revealed no significant shifts in the overall taxonomic composition of the active bacterial community. However, 12 of the 59 terminal restriction fragments identified showed significant changes in relative abundance during the tidal cycle. Changes in the relative abundance of three particular terminal restriction fragments (bacterial taxa) were positively correlated to the rate of extracellular hydrolysis. Losses of chlorophyll a and colloidal and cEPS (up to 50-60%) occurred mainly in the first 30 min after tidal cover. About half of this may be owing to in situ degradation, with ''wash away'' into the water column accounting for the remainder.Microphytobenthic biofilms in intertidal sediments play an important role in the ecology of estuarine systems (Under-1 Corresponding author (gjcu@essex.ac.uk).

Central Role of Dynamic Tidal Biofilms Dominated by Aerobic Hydrocarbonoclastic Bacteria and Diatoms in the Biodegradation of Hydrocarbons in Coastal Mudflats

“…constitutes 49% of the tidal biofilm community suggests that it plays a role in biofilm formation. However, biofilms also formed in the absence of oil and Alcanivorax, and so the contribution by species common to both oiled and nonoiled biofilms must be significant, notably diatoms that produce copious amounts of EPSs (20); the additional possibility that diatom EPSs emulsify hydrocarbons deserves investigation. Alcanivorax spp.…”

“…The detachment of surface biofilms is common in intertidal sediments, with ϳ15% of benthic chlorophyll a (indicative of diatom biomass) being washed away within 30 min of tidal cover in the Colne Estuary (20). Thus, the ability of aerobic hydrocarbonoclastic bacteria to live in a surface biofilm potentially provides another selective advantage by allowing dispersal on the tide, resulting in the tidal biofilms being stranded on the tide line, which is precisely where newly deposited or redistributed oil and, thus, a fresh source of carbon and energy would also appear.…”

Tracing carbon flow from microphytobenthos to major bacterial groups in an intertidal marine sediment by using an in situ 13C pulse‐chase method

“…In addition, we also measured 13 C labeling in bulk, water-extractable, and EDTA-extractable carbohydrates as well as SCOA in pore water using recently developed LC-IRMS methods to determine which intermediates were important in the transfer of organic matter from diatoms to heterotrophic bacteria. Although the relationship between diatom carbohydrates exudates and the heterotrophic bacterial community have been studied in intertidal sediments (Hanlon et al 2006;Haynes et al 2007;Bellinger et al 2009;Oakes et al 2012;Taylor et al 2013), we included SCOA as important intermediates in the anaerobic degradation of diatom material . The results were used to construct a conceptual model of the transfer of carbon in the diatom mat (Fig.…”

Growth form defines physiological photoprotective capacity in intertidal benthic diatoms

“…In addition, while the 'overflow' hypothesis is often proposed (Underwood and Paterson, 2003;Stal, 2009), it was never clearly proven. A few studies have shown a positive relationship between light intensity and EPS production (Underwood, 2002;Wolfstein and Stal, 2002) but other studies have reported a negative relation with light intensity and no relationship with nutrient limitation (Perkins et al, 2001;Hanlon et al, 2006). To date there is no information on EPS production in different benthic diatom growth forms, and only EPL species have been compared (Underwood and Paterson, 2003), showing no clear relationship between light response and EPS secretion.…”