Major Effect of Hydrogen Peroxide on Bacterioplankton Metabolism in the Northeast Atlantic

Reactive oxygen species such as hydrogen peroxide have the potential to alter metabolic rates of marine prokaryotes, ultimately impacting the cycling and bioavailability of nutrients and carbon. We studied the influence of H₂O₂ on prokaryotic heterotrophic production (PHP) and extracellular enzymatic activities (i.e., β-glucosidase [BGase], leucine aminopeptidase [LAPase] and alkaline phosphatase [APase]) in the subtropical Atlantic. With increasing concentrations of H₂O₂ in the range of 100–1000 nM, LAPase, APase and BGase were reduced by up to 11, 23 and 62%, respectively, in the different water layers. Incubation experiments with subsurface waters revealed a strong inhibition of all measured enzymatic activities upon H₂O₂ amendments in the range of 10–500 nM after 24 h. H₂O₂ additions also reduced prokaryotic heterotrophic production by 36–100% compared to the rapid increases in production rates occurring in the unamended controls. Our results indicate that oxidative stress caused by H₂O₂ affects prokaryotic growth and hydrolysis of specific components of the organic matter pool. Thus, we suggest that oxidative stress may have important consequences on marine carbon and energy fluxes.     

Enzymatic Activities and Prokaryotic Abundance in Relation to Organic Matter along a West–East Mediterranean Transect (TRANSMED Cruise)

The distribution of extracellular enzymatic activities (EEA) [leucine aminopeptidase (LAP), ?-glucosidase (GLU), alkaline phosphatase (AP)], as well as that of prokaryotic abundance (PA) and biomass (PB), dissolved organic carbon (DOC), particulate organic carbon and particulate total nitrogen (POC, PTN), was determined in the epi-, meso-, and bathypelagic waters of the Mediterranean Sea along a West-East transect and at one Atlantic station located outside the Strait of Gibraltar. This study represents a synoptical evaluation of the microbial metabolism during early summer. Decreasing trends with depth were observed for most of the parameters (PA, PB, AP, DOC, POC, PTN). Significant differences between the western and eastern basins of the Mediterranean Sea were found, displaying higher rates of LAP and GLU and lower C/N ratios more in the eastern than in the western areas. Conversely, in the epipelagic layer, PA and PB were found to be higher in the western than in the eastern basins. PB was significantly related to DOC concentration (all data, n = 145, r = 0.53, P < 0.01), while significant correlations of EEA with POC and PTN were found in the epipelagic layer, indicating an active response of microbial metabolism to organic substrates. Specific enzyme activities normalized to cell abundance pointed out high values of LAP and GLU in the bathypelagic layer, especially in the eastern basin, while cell-specific AP was high in the epi- and bathypelagic zone of the eastern basin indicating a rapid regeneration of inorganic P for both prokaryotes and phytoplankton needs. Low activity and abundance characterized the Atlantic station, while opposite trends of these parameters were observed along the Mediterranean transect, showing the uncoupling between abundance and activity data. In the east Mediterranean Sea, decomposition processes increased probably in response to mesoscale structures which lead to organic matter downwelling.     

Abundance and activity of Chloroflexi-type SAR202 bacterioplankton in the meso- and bathypelagic waters of the (sub)tropical Atlantic

The contribution of Chloroflexi-type SAR202 cells to total picoplankton and bacterial abundance and uptake of D- and L-aspartic acids (Asp) was determined in the different meso- and bathypelagic water masses of the (sub)tropical Atlantic (from 35 degrees N to 5 degrees S). Fluorescence in situ hybridization (FISH) revealed that the overall abundance of SAR202 was < or = 1 x 10(3) cells ml(-1) in subsurface waters (100 m layer), increasing in the mesopelagic zone to 3 x 10(3) cells ml(-1) and remaining fairly constant down to 4000 m depth. Overall, the percentage of total picoplankton identified as SAR202 increased from < 1% in subsurface waters to 10-20% in the bathypelagic waters. On average, members of the SAR202 cluster accounted for about 30% of the Bacteria in the bathypelagic waters, whereas in the mesopelagic and subsurface waters, SAR202 cells contributed < 5% to total bacterial abundance. The ratio of D-Asp : L-Asp uptake by the bulk picoplankton community increased from the subsurface layer (D-Asp : L-Asp uptake ratio approximately 0.03) to the deeper layers reaching a ratio of approximately 1 at 4000 m depth. Combining FISH with microautoradiography to determine the proportion of SAR202 cells taking up D-Asp versus L-Asp, we found that approximately 30% of the SAR202 cells were taking up L-Asp throughout the water column while D-Asp was essentially not taken up by SAR202. This D-Asp : L-Asp uptake pattern of SAR202 cells is in contrast to that of the bulk bacterial and crenarchaeal community in the bathypelagic ocean, both sustaining a higher fraction of D-Asp-positive cells than L-Asp-positive cells. Thus, although the Chloroflexi-type SAR202 constitutes a major bathypelagic bacterial cluster, it does not contribute to the large fraction of d-Asp utilizing prokaryotic community in the meso- and bathypelagic waters of the North Atlantic, but rather utilizes preferentially L-amino acids.     

Specific Composition and Distribution of Euphausiids in the Zone of the North Atlantic Subtropical Convergence

The euphausiid community was studied between the surface and upper bathypelagics northeast of the Azores Islands (46°–37° N, 14°–29° W) during the hydrological summer (August to September) of 1984 using a midwater trawl. In total, 11 species of euphausiids were identified. The two most common species, Meganyctiphanes norvegica and Thysanopoda acutifrons, were found in 43.8 and 40.8% of the samples, respectively. In terms of biomass, M. norvegica dominated the catches, its densities reaching up to 160 kg per trawling hour. The region is dominated by North Atlantic arctic–boreal and boreal species, followed by pan-oceanic meso- and bathypelagic, as well as tropical–subtropical and widespread tropical euphausiid species. The study area, which is situated in the zone of the Atlantic subtropical convergence, is subjected to seasonal migrations of the Subpolar Frontal system. Owing to this, a quasi-stationary ecotone is established, where arctic–boreal species are spatially replaced first by tropical–subtropical and then by widespread tropical elements. There are grounds to believe that the quasi-stationary ecotone lasts both for many years and from season to season. In the latter case, seasonal succession of species takes place, but the ecological structure of the ecotone remains almost constant.     

Major imprint of surface plankton on deep ocean prokaryotic structure and activity

Deep ocean microbial communities rely on the organic carbon produced in the sunlit ocean, yet it remains unknown whether surface processes determine the assembly and function of bathypelagic prokaryotes to a larger extent than deep‐sea physicochemical conditions. Here, we explored whether variations in surface phytoplankton assemblages across Atlantic, Pacific and Indian ocean stations can explain structural changes in bathypelagic (ca. 4,000 m) free‐living and particle‐attached prokaryotic communities (characterized through 16S rRNA gene sequencing), as well as changes in prokaryotic activity and dissolved organic matter (DOM) quality. We show that the spatial structuring of prokaryotic communities in the bathypelagic strongly followed variations in the abundances of surface dinoflagellates and ciliates, as well as gradients in surface primary productivity, but were less influenced by bathypelagic physicochemical conditions. Amino acid‐like DOM components in the bathypelagic reflected variations of those components in surface waters, and seemed to control bathypelagic prokaryotic activity. The imprint of surface conditions was more evident in bathypelagic than in shallower mesopelagic (200–1,000 m) communities, suggesting a direct connectivity through fast‐sinking particles that escape mesopelagic transformations. Finally, we identified a pool of endemic deep‐sea prokaryotic taxa (including potentially chemoautotrophic groups) that appear less connected to surface processes than those bathypelagic taxa with a widespread vertical distribution. Our results suggest that surface planktonic communities shape the spatial structure of the bathypelagic microbiome to a larger extent than the local physicochemical environment, likely through determining the nature of the sinking particles and the associated prokaryotes reaching bathypelagic waters.     

Latitudinal trends of Crenarchaeota and Bacteria in the meso- and bathypelagic water masses of the Eastern North Atlantic

The distribution and activity of the bulk picoplankton community and, using microautoradiography combined with catalysed reported deposition fluorescence in situ hybridization (MICRO-CARD-FISH), of the major prokaryotic groups (Bacteria, marine Crenarchaeota Group I and marine Euryarchaeota Group II) were determined in the water masses of the subtropical North Atlantic. The bacterial contribution to total picoplankton abundance was fairly constant, comprising approximately 50% of DAPI-stainable cells. Marine Euryarchaeota Group II accounted always for < 5% of DAPI-stainable cells. The percentage of total picoplankton identified as marine Crenarchaeota Group I was approximately 5% in subsurface waters (100 m depth) and between 10% and 20% in the oxygen minimum layer (250-500 m) and deep waters [North East Atlantic Deep Water (NEADW) and Lower Deep Water (LDW), 2750-4800 m depth]. Single-cell activity, determined via a quantitative MICRO-CARD-FISH approach and taking only substrate-positive cells into account, ranged from 0.05 to 0.5 amol D-aspartic acid (Asp) cell(-1) day(-1) and 0.1-2 amol L-Asp cell(-1) day(-1), slightly decreasing with depth. In contrast, the D-Asp:L-Asp cell-specific uptake ratio increased with depth. By combining data reported previously using the same method as applied here and data reported here, we found a decreasing relative abundance of marine Crenarchaeota Group I throughout the meso- and bathypelagic water column from 65 degrees N to 5 degrees N in the eastern basin of the North Atlantic. Thus, the relative contribution of marine Crenarchaeota Group I to deep-water prokaryotic communities might be more variable than previous studies have suggested. This apparent variability in the contribution of marine Crenarchaeota Group I to total picoplankton abundance might be related to successions and ageing of deep-water masses in the large-scale meridional ocean circulation and possibly, the appearance of crenarchaeotal clusters other than the marine Crenarchaeota Group I in the (sub)tropical North Atlantic.     

Macroecological patterns of archaeal ammonia oxidizers in the Atlantic Ocean

Macroecological patterns are found in animals and plants, but also in micro‐organisms. Macroecological and biogeographic distribution patterns in marine Archaea, however, have not been studied yet. Ammonia‐oxidizing Archaea (AOA) show a bipolar distribution (i.e. similar communities in the northernmost and the southernmost locations, separated by distinct communities in the tropical and gyral regions) throughout the Atlantic, detectable from epipelagic to upper bathypelagic layers (<2000 m depth). This tentatively suggests an influence of the epipelagic conditions of organic matter production on bathypelagic AOA communities. The AOA communities below 2000 m depth showed a less pronounced biogeographic distribution pattern than the upper 2000 m water column. Overall, AOA in the surface and deep Atlantic waters exhibit distance–decay relationships and follow the Rapoport rule in a similar way as bacterial communities and macroorganisms. This indicates a major role of environmental conditions in shaping the community composition and assembly (species sorting) and no, or only weak limits for dispersal in the oceanic thaumarchaeal communities. However, there is indication of a different strength of these relationships between AOA and Bacteria, linked to the intrinsic differences between these two domains.     

Contribution of Archaea to total prokaryotic production in the deep Atlantic Ocean

Fluorescence in situ hybridization (FISH) in combination with polynucleotide probes revealed that the two major groups of planktonic Archaea (Crenarchaeota and Euryarchaeota) exhibit a different distribution pattern in the water column of the Pacific subtropical gyre and in the Antarctic Circumpolar Current system. While Euryarchaeota were found to be more dominant in nearsurface waters, Crenarchaeota were relatively more abundant in the mesopelagic and bathypelagic waters. We determined the abundance of archaea in the mesopelagic and bathypelagic North Atlantic along a south-north transect of more than 4,000 km. Using an improved catalyzed reporter deposition-FISH (CARD-FISH) method and specific oligonucleotide probes, we found that archaea were consistently more abundant than bacteria below a 100-m depth. Combining microautoradiography with CARD-FISH revealed a high fraction of metabolically active cells in the deep ocean. Even at a 3,000-m depth, about 16% of the bacteria were taking up leucine. The percentage of Euryarchaeota and Crenarchaeaota taking up leucine did not follow a specific trend, with depths ranging from 6 to 35% and 3 to 18%, respectively. The fraction of Crenarchaeota taking up inorganic carbon increased with depth, while Euryarchaeota taking up inorganic carbon decreased from 200 m to 3,000 m in depth. The ability of archaea to take up inorganic carbon was used as a proxy to estimate archaeal cell production and to compare this archaeal production with total prokaryotic production measured via leucine incorporation. We estimate that archaeal production in the mesopelagic and bathypelagic North Atlantic contributes between 13 to 27% to the total prokaryotic production in the oxygen minimum layer and 41 to 84% in the Labrador Sea Water, declining to 10 to 20% in the North Atlantic Deep Water. Thus, planktonic archaea are actively growing in the dark ocean although at lower growth rates than bacteria and might play a significant role in the oceanic carbon cycle.     

Ease of solubilization of five marker enzymes in three preparations of rat renal brush border membranes

The ability of eight stripping agents to solubilize five marker enzymes from rat renal brush border membranes isolated by three different preparative methods was examined. Protein and enzyme activities - alkaline phosphatase (APase), L-leucine aminopeptidase (LAPase), gamma-glutamyl transpeptidase (GGTase), gamma-glutamyl hydrolase (GGHase) and maltase - solubilized by the treatments were expressed as percent of total activity recovered in excess of control values. The relative enzyme activity and the solubilization factor were determined for each marker enzyme in every treated sample and the treatments with the eight agents compared. Trypsin treatment released > 80% of LAPase and < 10% of total membrane protein. Papain treatment released only 16--23% of total membrane protein but most of the enzyme activities except APase. Neuraminidase had no solubilizing effect. 4--10% of total membrane protein was solubilized by LiCl treatment but no marker enzyme activities were released. Less total membrane protein was released by treatment with proteolytic enzymes or LiCl than with the detergents Triton X-100, hexadecyltrimethylammonium bromide, sodium deoxycholate, and sodium dodecylsulfate. APase activity was the least readily solubilized. Correlating the degree of solubilization for five marker enzymes with the types of stripping agents used and with the appearance of the membrane surface when examined by electron microscopy led to the suggestion that LAPase, GGTase, GGHase and maltase molecules are part of an interwoven surface layer of membrane proteins which can be disrupted by transamidation and transesterification reactions. APase appears to be more strongly associated with the intact lipid matrix than the bulk of the membrane protein.     

Contribution of Archaea to Total Prokaryotic Production in the Deep Atlantic Ocean

Fluorescence in situ hybridization (FISH) in combination with polynucleotide probes revealed that the two major groups of planktonic Archaea (Crenarchaeota and Euryarchaeota) exhibit a different distribution pattern in the water column of the Pacific subtropical gyre and in the Antarctic Circumpolar Current system. While Euryarchaeota were found to be more dominant in nearsurface waters, Crenarchaeota were relatively more abundant in the mesopelagic and bathypelagic waters. We determined the abundance of archaea in the mesopelagic and bathypelagic North Atlantic along a south-north transect of more than 4,000 km. Using an improved catalyzed reporter deposition-FISH (CARD-FISH) method and specific oligonucleotide probes, we found that archaea were consistently more abundant than bacteria below a 100-m depth. Combining microautoradiography with CARD-FISH revealed a high fraction of metabolically active cells in the deep ocean. Even at a 3,000-m depth, about 16% of the bacteria were taking up leucine. The percentage of Euryarchaeota and Crenarchaeaota taking up leucine did not follow a specific trend, with depths ranging from 6 to 35% and 3 to 18%, respectively. The fraction of Crenarchaeota taking up inorganic carbon increased with depth, while Euryarchaeota taking up inorganic carbon decreased from 200 m to 3,000 m in depth. The ability of archaea to take up inorganic carbon was used as a proxy to estimate archaeal cell production and to compare this archaeal production with total prokaryotic production measured via leucine incorporation. We estimate that archaeal production in the mesopelagic and bathypelagic North Atlantic contributes between 13 to 27% to the total prokaryotic production in the oxygen minimum layer and 41 to 84% in the Labrador Sea Water, declining to 10 to 20% in the North Atlantic Deep Water. Thus, planktonic archaea are actively growing in the dark ocean although at lower growth rates than bacteria and might play a significant role in the oceanic carbon cycle.     

Distribution of marine viruses and their potential hosts in Prydz Bay and adjacent Southern Ocean,Antarctic

Viruses play a key role in all marine ecosystems, and yet little is known of their distribution in Antarctic waters, especially in bathypelagic waters (>1000 m). In this study, the abundance and distribution of viruses and their potential hosts from the surface to the bottom of Prydz Bay, Antarctic, was investigated using flow cytometry. Viruses and autotrophs were abundant in nearshore and continental shelf waters, while heterotrophic bacteria and picoeukaryotes were abundant in offshore waters. Virus and bacteria abundances generally decreased with increasing depth but increased slightly just above the seafloor. Within the water column, maximum virus numbers coincided with the maximum values of chlorophyll a (when greater than 0.1 μg l^?1), in the surface and subsurface (25 m). In the open ocean, however, virus abundance usually correlated with bacterial abundance at greater depths (50, 300 and 500 m) where the surface chlorophyll a concentration was lower than 0.1 μg l^?1. Viral abundance was correlated with the host cell abundance, and this was different in different pelagic zones (bacteria and autotrophs (i.e., chlorophyll a concentration) in the epipelagic waters, picoeukaryotes and bacteria in mesopelagic waters and bacteria in bathypelagic waters). Principle component analysis and Pearson correlation analysis indicated that there was a close relationship between virus abundance and chlorophyll a, bacteria and nutrients (NO₂ + NO₃, phosphate and silicate), and picoeukaryote abundance was mainly correlated with water depth and salinity.     

Mitochondrial DNA analysis reveals three stocks of yellowfin tuna Thunnus albacares (Bonnaterre, 1788) in Indian waters

Yellowfin tuna (Thunnus albacares) is an epipelagic, oceanic species of family Scombridae found in tropical and subtropical region of Pacific, Indian and Atlantic Ocean. It is commercially important fish and accounts for 19 % of total tuna catches in Indian waters. In present study, population structure of yellowfin tuna was examined using sequence analysis of mitochondrial DNA from seven geographically distinct locations along the Indian coast. A 500 bp segment of D-loop region was sequenced and analysed for 321 yellowfin samples. Hierarchical analysis of molecular variance showed significant genetic differentiation among three groups (VE); (AG); (KO, TU, PO, VI, PB) analyzed (Φ _ST  = 0.03844, P ≤ 0.001). In addition, spatial analysis of molecular variance identified three genetically heterogeneous groups of yellowfin tuna in Indian waters. Results were further corroborated by significant value of nearest neighbour statistic (S _nn = 0.261, P ≤ 0.001). Thus finding of this study rejects the null hypothesis of single panmictic population of yellowfin tuna in Indian waters.     

Effects of the Pleistocene on the mitochondrial population genetic structure and demographic history of the silky shark (<Emphasis Type="Italic">Carcharhinus falciformis</Emphasis>) in the western Atlantic Ocean

The silky shark, Carcharhinus falciformis, is a large-bodied, oceanic-coastal, epipelagic species found worldwide in tropical and subtropical waters. Despite its commercial importance, concerns about overexploitation, and likely ecological significance of this shark as an upper trophic-level predator, understanding of its population dynamics remains unclear for large parts of its distribution. We investigated the genetic diversity, population structure and demographic history of the silky shark along the western Atlantic Ocean based on the use of 707 bp of the mitochondrial DNA control region (mtCR). A total of 211 silky sharks were sampled, originating from five areas along the western Atlantic Ocean. The mitochondrial sequences revealed 40 haplotypes, with overall haplotype and nucleotide diversities of 0.88 (± 0.012) and 0.005 (± 0.003), respectively. The overall population structure was significantly different among the five western Atlantic Ocean regions. Phylogenetic analysis of mtCR sequences from globally sourced silky shark samples revealed two lineages, comprising a western Atlantic lineage and western Atlantic—Indo-Pacific lineage that diverged during the Pleistocene Epoch. In general, tests for the demographic history of silky sharks supported a population expansion for both the global sample set and the two lineages. Although our results showed that silky sharks have high genetic diversity, the current high level of overexploitation of this species requires long-term, scientifically informed management efforts. We recommend that fishery management and conservation plans be done separately for the two western Atlantic matrilineal populations revealed here.     

Different methods and storage duration affect measurements of epilithic extracellular enzyme activities in lotic biofilms

Extracellular enzyme activity (EEA) is becoming increasingly common for measuring biofilm function in streams. Different methods for enzyme assays may yield results that cannot be compared among studies, and duration of sample storage may also affect EEAs, leading to erroneous conclusions. We compared two frequently used methods for measuring phosphatase (PHOS), leucine aminopeptidase (LAMP), β-glucosidase (GLU), and β-xylosidase (XYLO) by conducting assays with intact and disrupted epilithic biofilms grown on tiles in three streams. Storage duration effects on EEA were documented with intact and disrupted biofilms kept in the dark at 4°C for 3 and 5 days. Intact biofilms had significantly less EEA than disrupted biofilms for all enzymes (P < 0.01). The two methods gave conflicting EEA results among streams, and ratios of disrupted to intact EEAs for each enzyme were not consistent among the three streams. PHOS was significantly greater than day 1 measurements when stored as disrupted (Day 3 = 210%, Day 5 = 199% increases) and intact biofilms (Day 3 = 375%, Day 5 = 240% increases). LAMP activities were significantly less when stored as disrupted biofilms (Day 3 = ?49% decrease) and greater when stored as intact biofilms (Day 5 = 72% increase). GLU (Day 3 = 313% increase) and XYLO (Day 3 = 121%, Day 5 = 188% increases) were significantly greater when stored as intact biofilms. The magnitude of change for all EEAs was inconsistent among streams, indicating that a consistent correction factor cannot be used to account for variation associated with storage duration. Consistent methods must be used and storage time should be minimized, preferably to the day of sampling, for valid inter-study comparisons. Conclusions can significantly differ between the two methods, therefore having implications for inter-study comparisons, understanding of biofilm function and dynamics, and environmental management decisions.     

Distribution and feeding ecology of the Greenland shark (Somniosus microcephalus) in Greenland waters

Greenland sharks are widely distributed and most likely a highly abundant predator in arctic waters. Greenland sharks have previously been considered scavengers, but recent studies suggest that Greenland sharks also predate on live prey. In this study, distribution and feeding ecology in Greenland waters were investigated. Based on data from 25 years of surveys, Greenland sharks were usually caught at 400–700 m but were found at all depths between 100 and 1,200 m. Based on examination of stomachs from 30 Greenland sharks (total length of 258–460 cm), the most important prey items were Atlantic cod (65.6 % IRI), harp seal (9.9 % IRI), skates (5.2 % IRI) and wolffish (4.4 % IRI), but large geographical variations were observed. Prey composition and qualitative observations support the hypothesis of active predation. Consistent with other studies, the results of this work support the notion that the Greenland shark is an apex predator with the potential to influence trophic dynamics in the Arctic.     

Rapoport's bathymetric rule and the latitudinal species diversity gradient for Northeast Pacific fishes and Northwest Atlantic gastropods: evidence against a causal link

Aim Few studies have explicitly considered the recurrent pattern of declining species diversity and increasing geographical range size that exists for numerous taxa across a variety of physical gradients. We extend Stevens’ [ Stevens, G.C. (1996) Journal of Biogeography, 23 , 149] work on Rapoport's bathymetric rule, using a more complete latitudinal assemblage of Northeast Pacific fishes and new data from Northwest Atlantic gastropods, to show that bathymetrical range size and species diversity are not causally linked. Location Fishes from the Northeast Pacific (0°–60° N) and gastropods from the Northwest Atlantic (0°–74° N) distributed from the surface to depths greater than 200 m. Methods Species pools were divided into three bathymetrical subgroups: (1) species restricted to shallow waters, between the surface and 200 m, (2) species that occurred in waters, both shallow and deep of 200 m, and (3) species restricted to waters deeper than 200 m. Median bathymetrical range size and total number of species were plotted against latitude (2° bins) using Stevens’ method, for the entire species pool and individual bathymetrical groups. Results For both fishes and gastropods, the apparent link between extratropical diversity and bathymetrical range size is an artefact resulting from the disproportionately high number of shallow restricted species in tropical latitudes, and the loss of these species in temperate latitudes. Furthermore, the extratropical gradient in gastropod diversity and bathymetrical range size are decoupled by approximately 15°, and while the latitudinal pattern for diversity is consistent across bathymetrical groups, median bathymetrical range size is highly irregular. Main conclusions These results suggests that functional groups can contribute disproportionately to patterns apparent at larger scales and that analysis of ecographical patterns by subregion is a novel approach that can help resolve debates over causality when patterns are seemingly coincident.     

Diclofenac Mediated Demodulation of Alkaline Phosphatase and Renal Cortical Damage in Experimental Albino Mice

Diclofenac sodium is known to interfere with renal physiology by inhibiting prostaglandins. Previous studies indicate that various nephrotoxins damage proximal renal tubules by altering alkaline phosphatase (APase) activity. APase has been reported to be a function related marker in renal proximal tubular epithelia where it is highly expressed. Present investigation deals with toxicity caused in mice kidney at histological and biochemical levels after diclofenac administration. Diclofenac toxicity was assessed by localizing APase in kidney histochemically and biochemically. Intramuscular diclofenac administration (10 mg/kg/body wt) for 30 days exhibited substantial degeneration in kidney. A marked change in APase activity was observed in histochemical and biochemical studies. A change was noticed in specific activity of APase at different periods of diclofenac treatment. Decrease in specific activity of APase after 10 days (18.41 %) and 30 days (55.3 %) of diclofenac exposure was observed. However, an insignificant hike in APase was observed after 20 days of drug therapy. Similar trends in APase activity were evidenced by the electrophoretic analysis. Histological and ultrastructural observations also corroborated above mentioned findings. Present investigation gives an insight into probable mechanism of renal pathology caused by diclofenac administration in mice.     

Microbial ecoenzyme stoichiometry,nutrient limitation,and organic matter decomposition in wetlands of the conterminous United States

Microbial respiration (R_m) and ecoenzyme activities (EEA) related to microbial carbon, nitrogen, and phosphorus acquisition were measured in 792 freshwater and estuarine wetlands (representing a cumulative area of 217,480 km²) across the continental United States as part of the US EPA’s 2011 National Wetland Condition Assessment. EEA stoichiometry was used to construct models for and assess nutrient limitation, carbon use efficiency (CUE), and organic matter decomposition (? k). The wetlands were classified into ten groups based on aggregated ecoregion and wetland type. The wetlands were also assigned to least, intermediate, and most disturbed classes, based on the extent of human influences. Ecoenzyme activity related to C, N and P acquisition, R_m, CUE, and ? k differed among ecoregion–wetland types and, with the exception of C acquisition and ? k, among disturbance classes. R_m and EEA were positively correlated with soil C, N and P content (r = 0.15–0.64) and stoichiometry (r = 0.15–0.48), and negatively correlated with an index of carbon quality (r = ? 0.22 to ? 0.39). EEA stoichiometry revealed that wetlands were more often P- than N-limited, and that P-limitation increases with increasing disturbance. Our enzyme-based approach for modeling C, N, and P acquisition, and organic matter decomposition, all rooted in stoichiometric theory, provides a mechanism for modeling resource limitations of microbial metabolism and biogeochemical cycling in wetlands. Given the ease of collecting and analyzing soil EEA and their response to wetland disturbance gradients, enzyme stoichiometry models are a cost-effective tool for monitoring ecosystem responses to resource availability and the environmental drivers of microbial metabolism, including those related to global climate changes.     

Aging exo-enzymes can create temporally shifting,temperature-dependent resource landscapes for microbes

The rate at which catalytic capacity of microbial exo-enzymes degrades post-exudation will influence the time during which return on microbes’ investment in exo-enzyme production can be realized. Further, if exo-enzyme degradation rates vary across exo-enzymes, microbial investment returns may vary by element across time. We quantify how aging of two soil organic matter (SOM)-decaying enzymes (β-D-cellobioside, BGase; and N-acetyl-β-D-glucosaminide, NAGase) influences enzyme-substrate V _max at multiple temperatures (5, 15, 25 °C), and compute how enzyme age influences relative availabilities of C and N. Both BGase and NAGase exhibited similar, exponential declines in catalytic rate with age at 25 °C (0.22 ± 0.02 and 0.36 ± 0.14 d^?1, respectively). At 15 °C, NAGase exhibited exponential declines in catalytic rates with age (0.79 ± 0.31 d^?1), but BGase exhibited no decline. Neither enzyme exhibited a decline in catalytic rate over 72 h at 5 °C. At 15 °C, the amount of C liberated from cellulose and chitin analogues relative to N increased, on average, by more than one order of magnitude. The ratio of C:N liberated from the two substrates remained constant across enzyme age at 25 and 5 °C, but for different reasons: no differences in decay rate across enzymes at 25 °C, and no observed decay at 5 °C. Thus, temperature-dependent decreases of catalytic activity over time may influence microbial resource allocation strategies and rates of SOM decomposition. Because the enzyme decay rates we observed differ considerably from values assumed in most models, such assumptions should be revisited when parameterizing microbial process models.