Extracellular Enzyme Activity and Its Implications for Organic Matter Cycling in Northern Chinese Marginal Seas

Abstract

Extracellular enzymes, initiating the degradation of organic macromolecules, are important functional components of marine ecosystems. Measuring in situ seawater extracellular enzyme activity (EEA) can provide fundamental information for understanding the biogeochemical cycling of organic matter in the ocean. Here we investigate the patterns of EEA and the major factors affecting the seawater EEA of Chinese marginal seas. The geographic distribution of EEA along a latitudinal transect was examined and found to be associated with dissolved organic carbon. Compared with offshore waters, inshore waters had higher enzyme activity. All the tested substrates were hydrolyzed at different rates and phosphatase, β-glucosidase and protease contributed greatly to summed hydrolysis rates. For any particular enzyme activity, the contribution of dissolved to total EEA was strongly heterogenous between stations. Comparisons of hydrolysis rates of the polymers and their corresponding oligomers suggest that molecule size does not necessarily limit the turnover of marine organic matter. In addition, several typical enzyme-producing clades, such as Bacteroidetes, Planctomycetes, Chloroflexi, Roseobacter, Alteromonas, and Pseudoalteromonas, were detected in the in situ environments. These enzyme-producing clades may be responsible for the production of different enzymes. Overall, each enzyme was found to flexibly respond to environmental conditions and were linked to microbial community composition. It is likely that this activity will profoundly affect organic matter cycling in the Chinese marginal seas.

Characterization and PUFA production of Aurantiochytrium limacinum BUCHAXM 122 isolated from fallen mangrove leaves

“…Five extracellular enzymes including protease, lipase, urease, α-glucosidase, and phosphatase were produced by A. limacinum BUCHAXM 122, consistent with previous reports for other species of Aurantiochytrium [23,34] and also for Shizochytrium and Thraustochytrium [34]. Similar to the ecosystem in which A. limacinum is found, phosphatase, βglucosidase and protease are also found in the bacteria such as Planctomycetes, Chloroflexi, Roseobacter, Alteromonas and Pseudoalteromonas [35]. However, most bacteria that live in seawater, sediment, plants and animals produce lipase phosphatase and protease, and a few produce urease [36].…”

Simple Plant and Microbial Exudates Destabilize Mineral-Associated Organic Matter via Multiple Pathways

“…These results point to possible contributions of microbial metabolites such as organic acids or extracellular enzymes to MAOM mobilization. Both have recently been implicated in the release of MAOM, either through the displacement of weakly bound compounds or enzymatic hydrolysis of surface-bound polymers. , A recent study showed that ectomycorrhizal fungi growing in media facilitated the mobilization of polymeric MAOM from goethite. MAOM mobilization was attributed to the interplay of fungal metabolites coating the surfaces and extracellular enzymes depolymerizing complex MAOM, bypassing the desorption step .…”

Patterns of Structural and Functional Bacterioplankton Metacommunity along a River under Anthropogenic Pressure

“…At all sites, similar proportions of taxa were recorded. At the phylum level they were represented by Bacterioidetes, Proteobacteria and Actinobacteria (Figure 5), which have the ability to produce a variety of extracellular enzymes and have been identified as dominant bacterial taxa in both marine [57] and riverine [30] environments. With more than 18% share in the total microbial community in the middle river course, Flavobacterium dominated at the genus level (Figure 6).…”