Number Of Heterotrophic Bacteria Research Articles

Evaluation of the health of Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) distributed in the Çanakkale strait, Turkey

The observation of mortality in Mediterranean mussels (Mytilus galloprovincialis) distributed in the Çanakkale Strait in recent years was influential in developing the research question for this study. In this study, the presence of bacteria (Vibrio spp.) and parasites (Marteilia spp. and Haplosporidium spp.) in mussels collected from Kumkale, Kepez, and Umurbey stations in the Çanakkale Strait was investigated seasonally. Microbiological findings, histopathology, oxidative stress enzymes and their gene expressions, lipid peroxidation, lysosomal membrane stability, and changes in haemolymph were examined. In summer samples, both the defence system and the extent of damage were higher in gill tissue. In winter samples, enzyme activities and lipid peroxidation were found to be predominantly higher in digestive gland tissues. Histological examinations and Hemacolor staining revealed the presence of protozoan cysts, and for bacterial examination, molecular analysis performed after culturing revealed the presence of 7 Vibrio species. While the total numbers of heterotrophic bacteria detected in all samples were at acceptable levels, the predominance of Vibrio spp. numbers among the total heterotrophic bacteria detected in almost all samples were noteworthy. The total hemocyte count was calculated as 5.810(4)±0.58 (cells/mm3) in winter and 7.210(4)±1.03 (cells/mm3) in summer. These factors are considered to be possible causes of mussel mortality.

Biogeochemical features of the formation of Holocene sediments in Lake Dukhovoe (Eastern Baikalia)

A 6-meter core of Holocene sediments from Lake Dukhovoe was studied. As shown by the radiocarbon dating of lacustrine sediments, Lake Dukhovoe was formed in the Early Holocene (10 cal ka BP). The upper 180 cm of sediment is represented by sapropel, and the boundary of lake sediments is at 293 cm. This is an early stage of lake evolution, devoid of biogenic sedimentation. The microbiological studies of the sediment were carried out, which showed a high total number of heterotrophic bacteria in the upper (0–15 cm) and deeper (110–180 cm) sapropel intervals. Mineral bottom sediments (180–293 cm) are characterized by the presence of groups of phosphorus-reducing and ferromanganese bacteria. The contents of Na, Mg, Al, Si, Al, Ca, Fe, Mn, Zr and Cr in sapropel are within the average concentrations for the earth’s crust, and U and Mo exceed them.

HYDROCARBON CONTAMINATION IMPACT ON SANDY SOILS WITHIN THE DZUNBAYAN OIL FIELD (EASTERN MONGOLIA)

The data are presented on the particle-size distribution, content of hydrocarbons, n-alkanes in their composition and the number of microorganisms in the soils of Dzunbayan oil production area (Mongolia, the Eastern Gobi desert steppe). The soils studied are characterized by the dominance of sand and fluid fraction (99.50–99.8%) with particles of 2–20 μm. The soils show alkaline reaction (pH 8.2–8.7), they are slightly saline in the control areas and highly saline (water extract salinity 0.13–2.34‰) near the production well. The content of petroleum hydrocarbons (HC) in soils of the study area varied from 9 to 60 mg/kg, with a maximum near the well. The study of the molecular composition of n-alkanes revealed the dominance of long-chain homologues (66.3–79.2% of the total n-alkanes), occurring at various stages of physicochemical and microbiological weathering. According to a number of features, the microbial community of soils is characterized by a high degree of adaptation to the conditions of the arid zone, salinity, and high pH values; at the same time, these conditions limit the development of typical representatives of soil microbiocenoses, i.e., actinomycetes and, to a greater extent, microscopic fungi. The total number of heterotrophic bacteria (HBGs) in the studied soil samples varied within 1.22–3.49 million CFU/g of soil. The proportion of oil-oxidizing bacteria (NOB) was 12.6–18.9% OBA, which corresponded to the high adaptive capacity of the community to hydrocarbons. Specific climatic conditions, features of soil composition, as well as oil with a predominance of heavy paraffin fractions of the Dzunbayan deposit, characterize the low potential ability of soils to self-purify under the oil pollution.

Effects of dissolved organic carbon and total ammonia nitrogen concentrations with the same DOC/TAN on biofloc performance

The regulation of the carbon-to‑nitrogen ratio (C/N) is at the core of biofloc technology. This study compared the performance of bioflocs under different dissolved organic carbon (DOC) and total ammonia nitrogen (TAN) concentrations but the same DOC/TAN ratio. Dissolved organic carbon and total ammonium nitrogen were set at 200 mg/L and 10 mg/L (Group 200/10), 100 mg/L and 5 mg/L (Group 100/5), and 50 mg/L and 2.5 mg/L (Group 50/2.5), respectively. The TAN removal rates of groups A, B, and C were 1.89 ± 0.02 mg N/g TSS·h, 1.63 ± 0.03 mg N/g TSS·h, and 1.32 ± 0.02 mg N/g TSS·h, respectively, and the differences were significant (P < 0.05). At the phylum level, the microbial community structure was dominated by Proteobacteria, Bacteroidetes, Actinobacteria, Verrucomicrobia, and Planctomycetes. At the genus level, Gemmobacter, Hydrogenophaga, and Microbacterium were the dominant genera. Most of bacteria community differed significantly among the three groups. As the concentration of carbon and nitrogen sources increased, the Shannon index showed a decrease in bacterial diversity, and the number of heterotrophic bacteria significantly increased. The crude protein content of flocs in group A ((29.22 ± 0.20)%) was significantly lower than that in groups B ((30.56 ± 0.32)%) and C ((30.83 ± 0.20)%). In groups A and B with higher carbon and nitrogen concentrations, the copy numbers of genes related to nitrification were relatively low, but the copy numbers of genes related to denitrification were relatively high. Therefore, it can be concluded that with a ratio of 20 of DOC/TAN, increasing DOC and TAN concentrations led to a significant increase in TAN removal capacity, heterotrophic bacteria count, denitrification function gene copies, and crude protein content of bioflocs, and a decrease in bacterial diversity, nitrification function gene copies, and C/N of bioflocs (P < 0.05). These results suggest that the influence of DOC and TAN concentrations on bioflocs performance may be more significant than that of DOC/TAN, and should be fully considered in practical bioflocs technology systems.

Effect of Microbial Preparation and Biomass Incorporation on Soil Biological and Chemical Properties

In order to meet the global nutritional needs of a growing population, attempts are being made to develop strategies that can effectively offset the negative effects of intensive farming. The aim of this study was to investigate the effect of Effective Microorganisms (EM) preparation and organic matter incorporation on the soil microbiological and chemical features. The analyses included the number of heterotrophic bacteria, fungi, actinobacteria, cellulolytic, amylolytic and proteolytic microorganisms, and bacteria of the genus Azotobacter. The content of organic carbon, the total and mineral nitrogen forms of phosphorus, potassium, magnesium, and the pH were also determined. The application of an EM of higher dose combined with the manure and straw resulted in the highest abundance of heterotrophic bacteria (165.1 × 106 cfu g−1), actinobacteria (43.2 × 105 cfu g−1), cellulolytic (17.2 × 106 cfu g−1), and proteolytic bacteria (82.0 × 106 cfu g−1). The highest content of chemical parameters was always observed in the experimental variant, including biomass incorporation, accompanied by EM use. The novelty of our research is the analysis of the synergistic effect of the experimental factors studied on the microbiological and chemical parameters of arable soils.

Studying the Composition and Genesis of Organic Matter in Bottom Sediments of Polluted Small Watercourses in Khabarovsk City Territory

The distribution of organic matter, hydrocarbons, phytopigments, and ecological-trophic groups of microorganisms was studied in the bottom sediments of ten small tributaries of the Amur R. near Khabarovsk. The water showed high concentrations of organic matter, varying from 44.47 to 279.3 mg/L. The concentration of Corg in bottom sediments varied from 1.9 to 23.1% in different types of sediments; the amount of hydrocarbons reached 5081 mg/kg, exceeding the background level by a factor of up to 50. Studies of the molecular composition of hydrocarbons in sediments revealed in some streams the predominance (up to 100% of the total) of light (C8–C13) n-alkanes, typical of oil products and the products of vegetation combustion. High-molecular compounds dominated in HC composition in most watercourses, including n-alkanes, genetically associated with terrestrial vegetation, and heavy fractions of oil products with various levels of microbial degradation. Volatile organic compounds were quantitatively dominated by the products of microbiological transformation (acetaldehyde and methanol). In terms of the concentration of sedimentary pigments (up to 400 µg/g), the sediments of the majority of watercourses belong to the hypereutrophic type. The total abundance of microorganisms in water varied from 2.7 to 488.0 thousand CFU/mL; in sediments, it was distributed symbatically, but ranged from 0.1 to 19.3 million CFU/g. The number of heterotrophic bacteria in bottom sediments correlated with the parameter of overload of the self-purification capacity (r = 0.718), and the number of oil-oxidizing bacteria correlated with hydrocarbon concentration (r = 0.967), thus confirming the indication properties of this bacterial group.

Effect of different doses of trichloroisocyanuric acid on aquaculture pond water

Understanding the bacterial dynamics in aquaculture ponds is imperative for the assessment of disinfection efficiency and regulation of subsequent pond ecosystems. In this study, the objective was to evaluate the impact of trichloroisocyanuric acid (TCCA) (0.135 mg/L, LG; 0.405 mg/L, HG) on the water quality index, heterotrophic bacteria, microbial community and ecological function. Nine separated artificial customized tanks were inserted into the pond sediment to form relatively independent pond bodies with similar environments. 16S rRNA gene amplicon sequencing was used to evaluate the dynamics of bacterial relative abundance within 192 h. Furthermore, the functional composition of the microbial community was inferred. The results indicated that both doses of TCCA had little influence on water quality. The residual chlorine was lower than the detection limit (0.03 mg/L) in the both LG and HG within 30 min. The bacterial inactivation rate was 65.04% in the HG compared with the control group within 1 h., whereas the number of heterotrophic bacteria increased to 1.26 × 105 cfu/mL at 24 h. and 4.53 × 105 cfu/mL at 48 h., 6.03 and 6.38 times higher than the CG (P < 0.05), respectively. The TCCA in the HG significantly decreased the microbial diversity and changed the relative abundance of the pond at 24 h. and 48 h. There were 28 and 35 significantly different genera between the CG and HG (P < 0.05), and the relative abundance of Bacillariophyta in the HG was significantly higher than that in the CG at 24 h. and 48 h. (P < 0.05).There were 7 and 4 significantly different functions (except other function) between the HG and CG (P < 0.05) at 24 h. and 48 h., respectively. The results indicated that the active chlorine disappeared immediately after using TCCA, 0.405 mg/L active chlorine had a strong influence on the heterotrophic bacteria, microbial community and function, and the effect lasted for 96 h., whereas 0.135 mg/L TCCA usage had little influence on the pond water.

Biogeochemical Features of the Formation of the Holocene Sediments in Lake Dukhovoe at the Stage of Early Diagenesis in Eastern Baikalia

Abstract —A 6-meter core of the Holocene sediments in Lake Dukhovoe is studied. The material composition of the core is heterogeneous and has clear bedding. Lacustrine sediments are represented by the upper 293 cm. Each bed of the sediments is subjected to microbiological analysis. A high total number of heterotrophic bacteria is revealed in the upper (0–15 cm) and deeper (110–150 cm) sapropel intervals. Sulfate-reducing bacteria are identified only in Chrysophyceae cysts. The CaO/Fe2O3 ratio shows the degree of “carbonate content” of bottom sediments. It is low in the lake sapropel (0.2), which indicates the geochemical specificity (carbonate-free sapropel). Na, Mg, Al, Si, Al, Ca, Fe, Mn, Zr, and Cr concentrations in sapropel are within the average concentrations for the Earth’s crust, shale, and oceanic pelagic clays, while U and Mo concentrations exceed them. Phytoplankton is enriched in phosphorus (biogenic element) and chalcophile elements (Zn, Cd, Sn, Sb, Hg, Pb, and Cu), which characterize the pollution of the modern atmosphere of the Baikal region. Diagenetic processes result in the transformation of the pore waters, namely an increase in mineralization as compared to lake water, an increase in the concentrations of biogenic components (HCO3-, NH4+, NO3-, and PO43-) and a decrease in SO42-. Pyrite framboid accumulations are revealed in organomineral sediments below the horizon of 200 cm, and iron phosphates represented by vivianite are identified in sapropel.

Assessment and bioremediation of mercury pollutants by highly mercury-resistant bacteria immobilized in biochar from small-scale artisanal gold mining areas

Small-scale gold mining activities in Indonesia still use amalgamation techniques, which have the potential to cause mercury (Hg) pollution and affect the quality and number of microorganisms. Mercury-resistant bacteria can survive and adapt to mercury-exposed environments and can be developed as bioremediation agents. The bioremediation activity of these bacteria can be increased through immobilization using biochar. The results of observations of physicochemical qualities in three samples in the mining area, showed significant differences. The TOC in the rhizosphere soil sample of &lt;em&gt;Calliandra calothyrsus&lt;/em&gt; L. showed the significantly highest value at 14.5%, and the pH of the three samples indicated acidity and exhibited no difference (p&amp;lt;0.05). The highest concentration measured in the tailing sample was 9.9 ng/g (p&amp;lt;0.05). The number of heterotrophic bacteria in the rhizosphere soil was the highest at 7.2 × 10&lt;sup&gt;8&lt;/sup&gt; CFU/g. On the other hand, the number of mercury-resistant bacteria in the tailing sample showed the highest value of 6.3 × 10&lt;sup&gt;3&lt;/sup&gt; CFU/g. In the selection based on the toxicity profile of 30 mercury-resistant bacteria obtained, the highest results were observed in the LMP1B5 bacterial isolate from the river sediment, with 50% effective concentration (EC50) and minimum inhibitory concentration (MIC) values of 225 and 250 mg/L, respectively. Polyphasic identification based on phenotypic and genotypic characteristics using the 16S rRNA gene showed that the bacterial isolate was identified as &lt;em&gt;Escherichia fergusonii&lt;/em&gt;. The growth and mercury removal activity of &lt;em&gt;E. fergusonii&lt;/em&gt; LMP1B5 increased by 21% and 52%, respectively, after the immobilization with biochar. Thus, immobilized &lt;em&gt;E&lt;/em&gt;.&lt;em&gt; fergusonii&lt;/em&gt; LMP1B5 was effective in removing mercury pollutants.

МИКРОБИОЛОГИЧЕСКАЯ ХАРАКТЕРИСТИКА ГИДРОТЕХНИЧЕСКИХ СООРУЖЕНИЙ НЕКОТОРЫХ БУХТ Г. СЕВАСТОПОЛЯ

Hydraulic structures, which are constantly present in bays, are one of the factors affecting the condition of coastal waters. Microperiphyton, which is formed on hydraulic structures in coastal zones with varying degrees of anthropogenic and recreational pressure, has the greatest indicative value. Microbiological studies of periphyton significantly complement the characterization of the ecological state of the coast. This study presents data on the quantitative distribution of heterotrophic and hydrocarbon-oxidizing bacteria in the microperiphyton of silt deposits of the southern breakwater of Sevastopol Bay and the eastern breakwater of Kamyshovaya Bay. The total number of heterotrophic bacteria in the silt deposits of the southern breakwater generally ranged from 103 to 104 cells/ml, while that of the eastern breakwater mainly varied within 103–105 cells/ml. The results obtained indicate that the silty deposits in the considered water areas to the development of the analyzed groups of bacteria participating in the processes of self-purification of water areas, and their number does not depend on the depth. Data analysis showed that the number of heterotrophic bacteria in the eastern breakwater was higher than in the southern breakwater. Seasonal differences in the number of studied groups of bacteria were not revealed. It was found that the processes of self-purification of the marine environment from oil and petroleum products are more active on the outer side of the breakwater, and these processes are more pronounced on the southern breakwater.

Bacterioplankton status in the Lososinka River (a tributary of Lake Onego) and water quality by microbiological indicators

The results of our bacterioplankton study (total abundance; saprophytic, hydrocarbon oxidizing and phenol resistant bacteria; total microbial number, and coliform bacteria) in an urbanized tributary of Lake Onego in 2015 are presented. The lower reaches of the Lososinka River flow across the territory of Petrozavodsk city (Karelia) and receive 14 untreated drains of the urban storm sewers. Differences in the temporal abundance dynamics of bacteria which are the indicators of oil pollution, sanitary condition and saprobity were found in the reference and urban parts of the river. These changes are not related to the hydrological and temperature regime of the river and reflect the influence of the pollutant drainage from the urban area on the formation of the river bacterial community. A significant increase in all studied indicators of the quantitative development of bacterioplankton in the urban part of the river as compared to the reference part was revealed. The number of heterotrophic bacteria of various ecological-trophic groups decreases in the lake water by 8–16 times due to dilution, as early as 500 m from the mouth of the river. A significant decrease in the numbers of hydrocarbon oxidizing bacteria in the river water and an increase in sanitary-indicative microorganisms are shown to occur over four years. The Lososinka River on the territory of the Petrozavodsk city is assessed as polluted with oil products and organic matter of fecal origin and unsuitable for recreation according by the level of indicator bacteria.

Bioremediation potential of native microorganisms of the southern chernozem

In the course of the conducted studies, main groups of soil microorganisms in the southern chernozem were identified. The resistance of isolates to the action of oil in the concentration range of 15–25%, the possibility of using it as a carbon source, the ability of soil microbiota to biodegradate oil in contaminated soil and the resistance of bacteria to low temperatures, high NaCl concentrations, acid and alkali resistance were established. 15 genera (31 species) of heterotrophic bacteria were isolated from uncontaminated soil samples of the southern chernozem subtype. Our assessment of the abundance dynamics of microorganisms isolated from laboratory contaminated soils showed that as a result of oil exposure, there was a significant decrease in the numbers of microorganisms: by the 180th day of our experiment, 10 bacteria species belonging to 3 genera were isolated, namely: Bacillus, Micrococcus and Serratia. Among the isolated bacteria, resistance to the action of the pollutant at a concentration of 25% was established for B. coagulans, B. mojavensis, B. megaterium, M. luteus, as well as for the museum strain of B. pumilus CM. By cultivating the studied bacterial strains on a carbon-free medium M9 with 15 and 20% oil added, their ability to use petroleum hydrocarbons as the only carbon source was established; however, when the concentration increased to 25%, only M. luteus, B. mojavensis and B. pumilus KM retained this ability. The presence of hydrocarbon-oxidizing bacteria in soil samples contributed to the 42% decrease in the oil mass concentration in 180 days. The most significant decrease in the concentration of petroleum products occurred in the period from the 10th to the 30th day and amounted to 25%, which is probably due to the increase in the numbers of heterotrophic bacteria. The ability to grow at a temperature of +4°C was established for representatives of the genus Bacillus, including the museum strain of B. pumillus CM, 4 strains of bacilli remained viable in an acidic environment (pH 5), 7 strains of bacilli and M. luteus and S. plymuthica remained viable in an alkaline environment (pH 9). The studied bacterial strains were growing on a GRM-agar with a NaCl concentration of 7%, the ability to grow at a NaCl concentration of 15% was preserved only by the museum strain of B. pumillus KM. The obtained results open the prospects for the use of hydrocarbon-oxidizing bacteria with a high adaptive potential as potential oil destructors capable of biodegradation at low temperatures, in conditions of high salinity and in a wide range of pH of the medium.

In situ lysimeter experiment of leaching pollutants from municipal waste with physicochemical status and microbiome condition

• Effluents have a specific electrical conductivity similar to landfill leachates. • The microbiological activity in the tested leachate samples shows seasonality. • Temperatures in summer reduced the ability of the microbiome to oxidize polymers. Lysimeter tests are an ideal supplement to monitoring tests performed in the area of landfills. This article presents an interdisciplinary lysimeter experiment that used hydrogeological, biochemical, and microbiological studies to evaluate the process of leaching pollutants from waste. The obtained results of leachate tests indicate that the EC value was as high as 31 mS/cm which corresponds to poor water quality. Additionally, high concentrations of chlorides (up to 5095 mg/L) and sulphates (up to 10107 mg/L) were observed. The results of microbiological tests confirm the seasonality. The statistically significant (p < 0.05) difference in the number of heterotrophic bacteria was denoted between autumn (1.6·107 CFU cm-3) and winter (1.5·105 CFU cm-3.The analysis of the ability to utilize nitrogen and phosphorus sources showed seasonal differences in the use of substrates containing these biogenic elements. It was observed that nitrogen-containing compounds were most intensively used in winter and the least in spring while phosphorus compounds were the most intensively oxidized in summer. Presented results confirm that lysimeter studies can play a valuable role in the construction of landfills for the best method of waste isolation and limiting the growth of microorganisms.

ФИЗИКО-ХИМИЧЕСКИЕ УСЛОВИЯ В ВОДОРОСЛЕВЫХ МАТАХ И ИХ ВЛИЯНИЕ НА НЕКОТОРЫЕ ГРУППЫ ГИДРОБИОНТОВ В ГИПЕРСОЛЁНЫХ ВОДОЁМАХ (НА ПРИМЕРЕ ЗАЛИВА СИВАШ, КРЫМ)

The physical and chemical characteristics (salinity, temperature, pH) in algae mats of hypersaline Sivash Bay (Crimea) were studied. They were formed in the coastal waters of the bay and influence alive community condition. A significant tendence of the pH increase in the direction of shore-clear water was noted. This represents an improvement of oxygen conditions in the said direction. Heterotrophic and denitrifying bacteria had been isolated ubiquitously. The presence of a significant negative correlation between pH of th e water and the number of heterotrophic bacteria was noted. A slight negative correlation between pH of the water and the number of denitrifying bacteria was determined. Thus, there was a tendency for the inhibition of these bacteria groups’ growth by high pH. Salinity, in the range of its change (60.8–94.5 ‰), hadn’t a significant effect on the abundance of the studied groups of bacteria. In the detected range of temperature (23 –32 ˚С), it was impossible to assert the presence of a close relationship betwe en these parameters. In algal mats, there was a community of poor diversity. The macrocomponents were represented by Artemia salina (Linnaeus, 1758) and larvae of Chironomidae sp. Salinity in the studied range of values hadn’t affected the abundance and biomass of the components of the macrozoocommunity significantly. At the same time, a positive effect of changes in water pH on the abundance and biomass of A. salina was noted. This phenomenon for the larvae of Chironomidae sp. not fixed.

Quality of rainwater drained by a green roof in the metropolitan region of Recife, Brazil

The objective of this study was to evaluate the potential non-potable uses that can be given to the water flowing from a green roof through the characterization of its quality using the parameters and reference values contained in the Brazilian Standard ABNT NBR 15527:2007. The research was carried out in the Garage Building of the Charles Darwin Business, for a period of five months. Fifteen samples were collected from three collection points (rainwater, irrigation, and drainage from the green roof) and evaluated. For the qualitative characterization of the waters, the physicochemical parameters hydrogen potential (pH), turbidity (TBD), apparent color (AC), free residual chlorine (FRC) and electrical conductivity (EC), in addition to the microbiological parameters total coliforms, Escherichia coli and number of heterotrophic bacteria (HB), were determined. Data were subjected to descriptive and multivariate statistical analysis. The results obtained show that the green roof contributed to the reduction of rainwater pH. The green roof drainage water had higher levels of AC and TBD due to the concentrations of suspended particles, which acted as a source of EC. The FRC values complied with the legislation in all treatments. Likewise, the microbiological parameters partially complied with the standards established by the legislation. Cluster analysis formed two distinct groups, G1 comprising HB and TBD, and G2 containing the variables pH, AC, EC, and FRC. Although the quality of the drainage water does not meet all the standards required by law, this water has the potential for reuse for non-potable purposes.

Cultivation of Arthrospira platensis in Brewery Wastewater

Cultivation of photosynthetic microorganisms in wastewater is a potential cost-effective method of treating wastewater and simultaneously providing the essential nutrients for high-value biomass production. This study investigates the cultivation of the cyanobacterium Arthrospira platensis in non-diluted and non-pretreated brewery wastewater under non-sterile and alkaline growth conditions. The system’s performance in terms of biomass productivity, pollutant consumption, pigment production and biomass composition was evaluated under different media formulations (i.e., addition of sodium chloride and/or bicarbonate) and different irradiation conditions (i.e., continuous illumination and 16:8 light:dark photoperiod). It was observed that the combination of sodium bicarbonate with sodium chloride resulted in maximum pigment production recorded at the end of the experiments, and the use of the photoperiod led to increased pollutant removal (up to 90% of initial concentrations) and biomass concentration (950 mg/L). The composition of the microbial communities established during the experiments was also determined. It was observed that heterotrophic bacteria dominated by the phyla of Pseudomonadota, Bacillota, and Bacteroidota prevailed, while the cyanobacteria population showcased a dynamic behavior throughout the experiments, as it increased towards the end of cultivation (relative abundance of 10% and 30% under continuous illumination and photoperiod application, respectively). Overall, Arthrospira platensis-based cultivation proved to be an effective method of brewery wastewater treatment, although the large numbers of heterotrophic bacteria limit the usage of the produced biomass to applications such as biofuel and biofertilizer production.

Effects of low-light stress on aquacultural water quality and disease resistance in Nile tilapia.

Light intensity has an important environmental influence on the quality and yield of aquatic products. It is essential to understand the effects of light intensity on water quality and fish metabolism before large-scale aquaculture is implemented. In this study, two low-intensity light levels, 0 lx and 100 lx, were used to stress Nile tilapia (Oreochromis niloticus), with a natural light level (500 lx) used as control. The pH, dissolved oxygen and ammonia contents were significantly lower in the water used in the 0 lx and 100 lx groups than in controls, while the levels of nitrite and total phosphorus were apparently higher. Moreover, the numbers of heterotrophic bacteria, Vibrio and total coliforms in aquaculture water were 157.1%, 314.2% and 502.4% higher, respectively, after 0 lx light stress for 15 days. The survival rate of Nile tilapia decreased significantly to 90.6% under 0 lx light on the 15th day. Of the immune-related genes, the expressions of IFN-γ, IL-12 and IL-4 were 390.3%, 757.8% and 387.5% higher under 0 lx light and 303.3%, 471.2% and 289.7% higher under 100 lx light, respectively. These results indicate that low-intensity light changes the physicochemical parameters of aquaculture water and increases the number of bacteria it hosts while decreasing the survival rate and increasing the disease resistance of Nile tilapia.

Correlation between bacterial abundance, soil properties and heavy metal contamination in the area of non-ferrous metal processing plant, Southern Bulgaria

In the present study, the correlation between bacterial abundance and soil physicochemical properties along the heavy metal contamination gradient in the area of non-ferrous metal processing plant was assessed. Our results showed that bacterial abundance (number of heterotrophic bacteria and number of 16S rRNA gene copies) decreased with 45–56% (CFU) and 54–87% (16S rRNA gene) along the Zn, Pb and Cd contamination gradient. The total bacterial abundance (16S rRNA gene) increased exponentially in contrast to the abundance of heterotrophic bacteria. The reduction of bacterial abundance in heavily contaminated soil indicated that the soil properties (soil pH, total organic carbon, inorganic ions, soil texture) could modify the effects of heavy metals and the response of microorganisms to that stress in long-term contaminated soils.

High-Frequency Variability of Bacterioplankton in Response to Environmental Drivers in Red Sea Coastal Waters.

Autotrophic and heterotrophic bacterioplankton are essential to the biogeochemistry of tropical ecosystems. However, the processes that govern their dynamics are not well known. We provide here a high-frequency assessment of bacterial community dynamics and concurrent environmental factors in Red Sea coastal waters. Weekly sampling of surface samples during a full annual cycle at an enclosed station revealed high variability in ecological conditions, which reflected in changes of major bacterioplankton communities. Temperature varied between 23 and 34°C during the sampling period. Autotrophic (Synechococcus, 1.7–16.2 × 104 cells mL−1) and heterotrophic bacteria (1.6–4.3 × 105 cells mL−1) showed two maxima in abundance in spring and summer, while minima were found in winter and autumn. Heterotrophic cells with high nucleic acid content (HNA) peaked in July, but their contribution to the total cell counts (35–60%) did not show a clear seasonal pattern. Actively respiring cells (CTC+) contributed between 4 and 51% of the total number of heterotrophic bacteria, while live cells (with intact membrane) consistently accounted for over 90%. Sequenced 16S rRNA amplicons revealed a predominance of Proteobacteria in summer and autumn (>40%) and a smaller contribution in winter (21–24%), with members of the Alphaproteobacteria class dominating throughout the year. The contribution of the Flavobacteriaceae family was highest in winter (21%), while the Rhodobacteraceae contribution was lowest (6%). Temperature, chlorophyll-a, and dissolved organic carbon concentration were the environmental variables with the greatest effects on bacterial abundance and diversity patterns.

Effect of Imidacloprid on the Microbial Biodiversity of Soils of Selected Zones of Haryana, India

Imidacloprid is one of the most frequently used insecticide in Haryana having a pivotal role in pest management and improvement in crop yield production. This study was performed to investigate the consequences of Imidacloprid on bacterial, actinomycetes and fugal population in soils of selected zones of Haryana, India. The experiment was conducted for 28 days and the samples were taken after 1st, 7th, 14th, 21st and 28th day of Imidacloprid application at various concentrations like T1(1mg/kg), T2 (2mg/kg) and T3(10mg/kg) doses. The number of CFU (colony forming unit) of microbes were grown on appropriate media using serial dilution and spread plate method. The results obtained showed a negative effect of Imidacloprid at T1 and T2 doses in first two weeks of incubation but non-significant effect in last two weeks of incubation on soil microbial number. Imidacloprid stimulated number of heterotrophic bacteria and fungi at T3 with time but a negative effect of N2- fixing and phosphate solubilizing bacteria was observed at each dose and time point in each soil sample. Obtained results showed that these soil microbes were affected by concentration and treatment time of Imidacloprid significantly in soils of each selected zone of Haryana. The results provide a clue about the possible ecological effects of Imidacloprid.