Influence of Light on Particulate Organic Matter Utilization by Attached and Free-Living Marine Bacteria

Abstract

Light plays a central role on primary productivity of aquatic systems. Yet, its potential impact on the degradation of photosynthetically produced biomass is not well understood. We investigated the patterns of light-induced particle breakdown and bacterial assimilation of detrital C and N using 13 C and 15 N labeled freeze-thawed diatom cells incubated in laboratory microcosms with a marine microbial community freshly collected from the Pacific Ocean. Particles incubated in the dark resulted in increased bacterial counts and dissolved organic carbon concentrations compared to those incubated in the light. Light also influenced the attached and free-living microbial community structure as detected by 16S rRNA gene amplicon sequencing. For example, Sphingobacteriia were enriched on dark-incubated particles and taxa from the family Flavobacteriaceae and the genus Pseudoalteromonas were numerically enriched on particles in the light. Isotope incorporation analysis by phylogenetic microarray and NanoSIMS (a method called Chip-SIP) identified free-living and attached microbial taxa able to incorporate N and C from the particles. Some taxa, including members of the Flavobacteriaceae and Cryomorphaceae, exhibited increased isotope incorporation in the light, suggesting the use of photoheterotrophic metabolisms. In contrast, some members of Oceanospirillales and Rhodospirillales showed decreased isotope incorporation in the light, suggesting that their heterotrophic metabolism, particularly when occurring on particles, might increase at night or may be inhibited by sunlight. These results show that light influences particle degradation and C and N incorporation by attached bacteria, suggesting that the transfer between particulate and free-living phases are likely affected by external factors that change with the light regime, such as time of day, water column depth and season.

Community structure of actively growing bacteria in a coastal fish-farming area

“…Bacteroidetes bacteria were also determined to be dominant particle-attached AGB (Table 3), in accordance with previous studies [10][11][12][13]. These bacteria are also dominant in both coastal and open oceans, accounting for more than half of the total bacterial cells in some reports, especially on particulate organic detritus [46].…”

“…Yoshikawa et al [8,9] clearly showed that hydrolysis and mineralization are higher in sinking particles than in seawater and bottom sediments, suggesting that sinking particles are one of the key sites of microbial hydrolysis and mineralization in aquaculture environments. Previous studies analyzing the community structures of particleattached bacteria [10][11][12][13] showed that Gammaproteobacteria and Bacteroidetes frequently dominated these particles. Further, most studies have focused on describing the general phylogenetic affiliations of these particle-attached bacteria, but information on actively growing species is limited.…”

Metaproteomics Reveals Similar Vertical Distribution of Microbial Transport Proteins in Particulate Organic Matter Throughout the Water Column in the Northwest Pacific Ocean

“…The taxonomic and functional structures of the microbial community also differed in each layer ( Supplementary Figures 5 , 6 ). Based on previous studies of both particle-attached and free-living microbes in different regions ( Zhang et al, 2007 ; Li et al, 2015 ; Mestr et al, 2017 ; Mestre et al, 2017 ; Gómez-Consarnau et al, 2019 ; Sebastián et al, 2019 ; Mestre et al, 2020 ), as well as a study on particulate-derived experimental isolates ( Enke et al, 2018 ), the particle-attached microbes accounted for the greater proportion, up to 73.69% in our data. In addition, pilin proteins (based on KEGG functional annotation), which constitute the defining characteristic of particle-attached microbes ( Maier and Wong, 2015 ), were detected in the dominant microbial groups, further demonstrating that these bacteria were particle attached.…”

Differential recruitment of opportunistic taxa leads to contrasting abilities in carbon processing by bathypelagic and surface microbial communities

“…S4, Table S2). This group of bacteria are also copiotrophs with a preference for a particle‐associated lifestyle (Li et al ., 2015; Mestre et al ., 2018; Gómez‐Consarnau et al ., 2019) and may reach relatively high abundances in the bathypelagic realm (Salazar et al ., 2016; Mestre et al ., 2018). The increase in bathypelagic Rhodobacterales in late time points of the experiment and the sustained heterotrophic production throughout the experiment suggest they were able to exploit the remaining DOM compounds after Alteromonas had exhausted the most labile DOM, pointing to a succession of specialized opportunistic taxa.…”