Bacteria In Biogeochemical Cycles Research Articles

Response of microbial communities and biogeochemical cycling functions to sediment physicochemical properties and microplastic pollution under damming and water diversion projects

Understanding the interactions among flow-sediment, microorganisms, and biogeochemical cycles is crucial for comprehending the ecological response mechanisms of dams and water diversion. This study focused on the spatial patterns of carbon, nitrogen, phosphorus, and sulfur (CNPS) cycle functional genes in the water resource for the middle route of the South-to-North Water Diversion Project in China, specifically the Danjiangkou Reservoir (comprising the Han and Dan reservoirs). The investigation incorporated sediment physicochemical properties and microplastic pollution. Numerous microbial species were identified, revealing that microbial communities demonstrated sensitivity to changes in sedimentary mud content. The communities exhibited greater β diversity due to finer sediment particles in the Han Reservoir (HR), whereas in the Dan Reservoir (DR), despite having higher sediment nutrient content and MPs pollution, did not display this pattern. Regarding the composition and structure of microbial communities, the study highlighted that sediment N and P content had a more significant influence compared to particle size and MPs. The quantitative microbial element cycling (QMEC) results confirmed the presence of extensive chemolithotrophic microbes and strong nitrogen cycle activity stemming from long-term water storage and diversion operations. The denitrification intensity in the HR surpassed that of the DR. Notably, near the pre-dam area, biological nitrogen fixation, phosphorus removal, and sulfur reduction exhibited noticeable increases. Dam construction refined sediment, fostering the growth of different biogeochemical cycling bacteria and increasing the abundance of CNPS cycling genes. Furthermore, the presence of MPs exhibited a positive correlation with S cycling genes and a negative correlation with C and N cycling genes. These findings suggest that variations in flow-sediment dynamics and MPs pollution have significant impact the biogeochemical cycle of the reservoir.

A survey on cultivable heterotrophic bacteria inhabiting a thermally unstratified water column in an Atlantic Rainforest lake.

Due to the importance of heterotrophic bacteria in biogeochemical cycles and their influence on water quality, many studies have assessed the composition of the bacterial community. Most of these were made in temperate freshwaters. Eighteen heterotrophic bacteria communities distributed over time and space in the water column of Carioca Lake, not exposed to anthropogenic activities, were analyzed to characterize their composition. A polyphasic approach was used, including 16S rDNA restriction analysis, 16S rRNA gene sequence analysis, BIOLOG Ecoplates and statistical methods. The physiological profiles among the 18 microbial communities were diverse. Clustering analysis and the metabolic fingerprint of the Biolog EcoplateTM system data separated the communities based on temporal scale. A set of 673 isolates were recovered on high nutrient medium. The 673 isolates obtained yielded 360 Amplified Ribosomal DNA Restriction Analysis (ARDRA) Operational Taxonomic Units (OTUs). Most (313) of the ARDRA patterns, OTUs, were from isolates obtained in a single sampling point, in temporal and spatial scales, indicating changes in the bacterial community. A subset of representative isolates for each ARDRA OTU was identified by 16S rRNA gene fragment sequencing and categorized into five phyla, Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Deinococcus-Thermus, represented by 38 genera. The results of this work contribute to a better understanding about the phylogeny of tropical freshwater heterotrophic bacteria.

Bacterial aox genotype from arsenic contaminated mine to adjacent coastal sediment: Evidences for potential biogeochemical arsenic oxidation

The potential biogeochemical redox activity of arsenic was investigated by examining bacterial arsenic (As) redox genes such as aox, ars, and arr in arsenic-contaminated abandoned mine area and adjacent coastal sediments. Consistent with aerobic sediment and water samples from the mine through coastal areas, bacterial genes involing arsenic(V) (arsenate, AsO(4)(3-)) reduction such as arsC and arrA were identified only in a few samples, where's bacterial aoxB gene encoding arsenite oxidase which is a central role in arsenic(III) (AsO(2)(-)) oxidation of aox operon. This study suggests that evaluation of arsenite-oxidizing bacteria including aox genotype may lead to a better understanding of molecular geomicrobiology in arsenic biogeochemistry, which can be applied to the bioremediation of arsenic contaminated mines along the coast of Gwangyang Bay. In this study, high concentrations of arsenic were observed in the mines and Gwangyang Bay and it was speculated that As(III)-oxidizing bacteria isolated from those highly arsenic-contaminated areas contributed the biogeochemical cycling of arsenic by transforming arsenic species and resulting in change of mobility, though further in situ biogeochemical and/or microbial ecological investigations are needed for confirming the phenomena in natural environment. Acinetobacter junni and Marinobacter sp. which were isolated in the contaminated area contained the aox genes and were able to oxidize As(III) to As(V), which is a more soluble form in oxic aqueous environments and apt to migrate from the mine to the coast. This might suggest a potential of a significant redox role of aox genes of arsenic-oxidizing bacteria in biogeochemical cycle of arsenic.

Fish stocking density induced growth responses of some biogeochemical cycling bacterial population

Experiment was performed to ascertain the effect of fish stocking density on population growth performance of some biogeochemical cycling bacteria in carp culture system. Advanced fry of Catla catla L., Labeo bata Ham. and Cyprinus carpio L. were introduced into tanks @ 8, 13, 16 and 32 fry tank-1 maintaining the ratio of C. catla -2 : L. bata -3 : C. carpio -3. Each tank was fertilized with mixed fertilizer @ 200 g week-1 during the rearing period of 150 days. Water samples were collected for examination of bacterial population, primary productivity and water quality parameters at weekly and biweekly intervals. Growth of fish was recorded at regular intervals. Statistical analysis of collected data was done by ANOVA and LSD for separation of mean (P < 0.05). Bacterial growth rate and productivity tended to rise with increasing stocking density showing maximum at stocking density 32 fry tank-1 whereas, fish growth exhibited an increasing trend upto stocking density 16 fry tank-1 and declined in further increment of fish density. Stocking density dependent growth efficiency of different bacteria (heterotrophic bacteria, cellulose decomposing bacteria, denitrifying bacteria and phosphate solubilizing bacteria) varied from 18 to 62.7%, 45 to 140%, 61 to 238% and 79 to 382% in stocking density 8, 13, 16 and 32 fry tank-1 , respectively. Results clearly revealed that higher stocking density of fishes liberates higher quantity of faecal matter containing proportionately greater amount of nutrients having more scope for bacteria to act upon the faecal matter resulting in higher bacterial population and productivity in one hand and fish growth inhibition due to stressful and uncongenial environmental condition developed by means of heavy nutrient load on the other hand. Therefore, it may be concluded that stocking density influencing the growth of biogeochemical cycling bacterial population in fish culture system.

Responses of some bio-geochemical cycling bacteria and their activities to management protocols under polyculture with Indian major carps and freshwater giant prawn

Abstract Estimations of the population size of some biogeochemical cycling bacteria and their activities were made in outdoor tanks (4500 l) in triplicate used for four treatments: monoculture of freshwater giant prawn, mixed culture of Indian major carps (catla and rohu) and polyculture of Indian major carps and freshwater giant prawn and a reference control with application of feed alone during the grow out period of 125 days, while maintaining the same initial manural dose and supplementary diet for all the treatments. Enumeration of different groups of bacteria at regular intervals from water and sediment samples of these tanks revealed that mean counts of heterotrophic bacteria — HB (water — 11.81 × 10 3 ml − 1 , sediment — 33.8 × 10 5 g − 1 ), ammonifying bacteria — AB (water — 9.65 × 10 3 ml − 1 , sediment — 28.8 × 10 5 g − 1 ), protein mineralizing bacteria — PMB (water — 1.86 × 10 3 ml − 1 , sediment — 18.45 × 10 5 g − 1 ) and nitrifying bacteria — NB (water — 33.66 × 10 3 ml − 1 , sediment — 13.62 × 10 4 g − 1 ) were distinctly reduced (ANOVA, P P A (water — 3.93 × 10 3 ml − 1 , sediment — 17.06 × 10 5 g − 1 ), anaerobic cellulose decomposing bacteria — CDB An (water — 1.50 × 10 3 ml − 1 , sediment — 44.26 × 10 5 g − 1 ) and Vibrio sp. (water — 11.21 × 10 3 ml − 1 , sediment — 39.21 × 10 5 g − 1 ) in the mixed carp culture than the rest. Reduction in the counts of bacteria in the carp–prawn polyculture implied a better utilization of feedlot resulting in less accumulation of feed remnants by the compatible and symbiotic association of fish and prawn. As a consequence, a clearly more balanced ecosystem and benign environment with reduced level of feedlot-dependent pollutants has been developed. It becomes apparent that main differences among the culture systems were the function of organic matter utilization which was zero in the control, and maximal in the polyculture and the resulting organic substrates accumulation in the water. In the carp–prawn polyculture, there was significant reduction in the counts of those groups of biogeochemical cycling bacteria (AB, PMB, NB, CDB An , Vibrio sp.) which mostly belong to the Gram-negative group. This indicates the possibility of exploiting carp–prawn polyculture as an associative system for reducing the Gram-negative water borne enteropathogenic bacteria that causes epidemiological problems.

Cadmium induced adaptive responses of certain biogeochemical cycling bacteria in an aquatic system

The population growth of some biogeochemical cycling bacteria (heterotrophic bacteria (HB), ammonifying bacteria (AB), ammonia oxidizing bacteria (AOB), denitrifying bacteria (DNB) and cellulose decomposing bacteria (CDB)), as well as ammonification, and denitrification rates were determined in simulated pond systems treated with full doses (FDs) and split doses (SDs) of cadmium. Reductions in bacterial density and nitrogen activity rates were more severe for the FD and SD followed by a slight recovery in both. Among the test groups, reductions were maximal in the AOB and DNB and lowest for the CDB populations, suggesting that the latter had greater potential for cadmium resistance. Bicarbonate alkalinity of water was found to exert a profound influence in counteracting cadmium stress in the system, as strong negative correlations between this parameter and bacterial mass were evident in the SD treatment. Though the aquatic microbial populations were greatly altered by cadmium stress, the normal operating range of the system was restored at a later time with the CDB population showing higher degree of adaptive responses.

Biogeochemical cycling bacterial activity in response to lime and fertilizer applications in pond systems

Lime-induced changes of biogeochemical cycling bacteria were examined using doses of 25, 50, 100, 200, 500, 1000 and 2000 kg ha−1 in the first part, and post-lime inorganic and organic fertilization in the second part of the experiment. Heterotrophic, ammonifying, denitrifying, cellulose decomposing and phosphate solublizing bacteria were drastically reduced by 30–90% in 1000 kg ha 21and 51D91% in 2000 kg ha−1. Density differences were minor in the remaining test doses for all groups of bacteria except for the dinitrifiers which were reduced in 500 kg ha−1 by 90% over the control. Similarly, reduced rates of ammonification, nitrification and denitrification were dose-dependent. Inorganic fertilization following lime application of 2000 kg ha−1 resulted in no marked increment of the counts of bacteria and activity processes, whereas organic manuring increased the density (50–200%) and the activities (212–292%) as well. Lime-induced changes of bacterial population and activities were explained as a result of high pH stress as well as a major shift in the CO2-HCO3-CO3 equilibrium system. Increase of major nutrients in the post-lime organic treatment was significantly higher than that of inorganic fertilization resulting in favourable N/P ratio and water quality conducive to fish farming after 45 days of liming.