Evaluation of microbiological water quality in the Pettaquamscutt River (Rhode Island, USA) using chemical, molecular and culture-dependent methods

We evaluated microbiological water quality in the Pettaquamscutt River (Rhode Island, USA), an estuarine river. Fecal coliform (FC) and enterococci (FE) bacteria, presence of Bifidobacterium adolescentis DNA (indicating human fecal contamination), and optical brightener (OB) fluorescence (associated with laundry detergents) were determined for 14 stations from May to September 2010. Six stations had high counts of FE and FC, and the presence of B. adolescentis DNA and high OB fluorescence indicated human fecal contamination - four had septic systems as likely sources of contamination; the others were in sewered areas. The ability of FC and FE to indicate human fecal contamination was assessed against a positive B. adolescentis test. FC and FE had false positive rates of 25% and 17%, respectively, and false negatives of 44% for FC and 63% for FE. Inclusion of molecular and chemical indicators should improve tracking of human fecal contamination sources in the river.     

使用反应器培养钝顶螺旋藻(Spirulina plarensis)过程中细菌群落的组成变化

使用气升式光生物反应器培养钝顶螺旋藻25天,发现随螺旋藻生物量的增长,细菌生物量有一定的增长趋势.应用PCR-DGGE技术分析螺旋藻培养过程中细菌种类组成,发现在不同时期细菌群落组成变化明显.通过DGGE图谱中18条特征条带的克隆、测序及系统进化分析,发现其中有8条序列与а变形菌纲序列相似,3条与拟杆菌纲序列相似,2条...     

Entrainment of E. coli and Listeria monocytogenes from sediment in irrigation canal

E. coli and Listeria monocytogenes (or L. monocytogenes) are bacteria affecting fresh produce that is harmful for health of humans and animals. If these bacteria are present in surface waterbody (e.g., irrigation canals), they will impair irrigation water quality and threaten produce safety. This paper studied the resuspension of E. coli and Listeria from bed sediment into irrigation water through several sets of laboratory experiments in an open channel flume. We studied three types of sediments using several flow rates in different velocities and shear stress. Bacteria's concentration in water increases with the bed shear stress. Two empirical relations were derived to correlate the concentration of E. coli and L. monocytogenes with the dimensionless bed shear stress. The experimental data favorably verified the relationships for sandy loam, loamy sand, and loam. The results showed that both bacteria could entrain from sand more efficiently compared to other sediments (i.e., sandy loam or loam). These relationships can be applied to water quality models for simulating E. coli and L. monocytogenes transport in irrigation canals for better managing irrigation water quality.     

Coupling Interactions between Electrokinetics and Bioremediation for Pyrene Removal from Soil under Polarity Reversal Conditions

This paper investigates the hybrid technology of electrokinetics (EK) coupled with bioremediation (Bio) in the removal of pyrene (PYR) in a soil matrix. Five different treatments were conducted to investigate the coupling interactions between EK and Bio on PYR degradation. A simulated removal curve was obtained by combining the degradation curves in EK‐ and Bio‐only experiments. The results show that the simulated curve fitted well with the actual degradation curve in electro‐bioremediation (EK‐Bio) experiments for the first 30 days of the experiment, while at later stages a discrepancy was found. This discrepancy was caused by adverse effects of low soil pH (3.6) near the anode on bacteria health during EK treatments. With polarity reversal (PR) to control the soil pH, the simulated curve fitted very well (r > 0.99) with the actual degradation curve during the whole treatment period. At the end of the experiment, PYR removal amounted to 63% with EK‐Bio treatments in PR electric fields, which was 1.7 times that of Bio‐only. Moreover, the bacteria counts under electric fields were more than that without EK. The spatial distributions of PYR degradation and bacterial counts were also investigated. The results show that they were both higher nearer the electrodes under PR electric fields.     

Microbial activity and biogeochemical cycling in a nutrient-rich meromictic acid pit lake

Microbial activity, abundance and biomass, and biogeochemical cycling of iron, sulphur and carbon were studied in the extremely acidic (pH 2.5-4.3), meromictic, nutrient-rich pit lake Cueva de la Mora in Spain. The goal was to find out (1) if the relatively high nutrient content influenced plankton abundance in the water column and alkalinity-producing microbial processes in the sediments compared to other acid pit lakes, and (2) if sediments in the shallow, mixed and the deep, stagnant parts of the lake exhibited differences in microbial activities and geochemical sediment composition related to meromixis. We hypothesised that redox cycling was more intense in the mixed part and higher amounts of reduced components would accumulate in the stagnant part. Especially phytoplankton biomass, CO₂ production, and sulphate reduction were indeed higher than reported from typical acid pit lakes and were rather within the range of neutral or weakly acidic lakes, which can be attributed to the relatively high nutrient contents of Cueva de la Mora. Even in the monimolimnion, anaerobic processes occurred mainly in the sediments. Sediments from the mixed and stagnant parts of the lake differed markedly in their biogeochemistry. Mixolimnetic sediments showed high iron and sulphate reduction rates, and they appeared to undergo substantial recycling, as supported by reactive Fe, relation between gross sulphate reduction rate and net accumulation of reduced sulphur, and viable counts of iron and sulphur bacteria. Monimolimnetic sediments exhibited lower anaerobic microbial activities, and surprisingly they accumulated more Fe(II) than mixolimnetic sediments, but less reduced sulphur and carbon. This might be explained by a strong separation of the two water bodies, resulting in comparably less input of energy (light) and allochthonous matter into the monimolimnion. Regarding the total extent of alkalinity-generating microbial processes, their net effect is not sufficient to neutralise the lake within decades.     

Impacts of the wintertime mesozooplankton community to downward carbon flux in the subarctic and subtropical Pacific Oceans

We compared wintertime depth distributions of the mesozooplankton community and dominant copepods between the subtropical (S1) and subarctic (K2) Pacific Oceans to evaluate the relative importance of actively transported carbon by vertical migrants to sinking particulate organic carbon flux. Primary production was higher and the ratio of sinking particulate organic carbon flux to primary production was lower at S1 compared with those at K2. The mesozooplankton community was lower in abundance and biomass at S1 compared to K2. Copepods were the dominant group among both mesozooplankton abundance and biomass throughout the water column down to 1000 m at both sites. The depth distribution showed that diel vertical migration was obvious for the mesozooplankton abundance and biomass at S1 but was not apparent for the abundance at K2, because the dominant component was diurnally migrating species at S1 and overwintering species residing at mesopelagic depths at K2. The major components of diel migrants were copepods and euphausiids at S1 and only euphausiids at K2. Respiratory flux by the diurnally migrating mesozooplankton was estimated to be 2 mgC m⁻² day⁻¹ at S1 and 7 mgC m⁻² day⁻¹ at K2. The respiratory flux was equivalent to 131% of sedimentary fecal pellet flux at S1 and 136% of that at K2. Because pathways of downward carbon flux are facilitated by the mesozooplankton community, the actively transported carbon (respiration of dissolved inorganic carbon, excretion of dissolved organic carbon and egestion of fecal pellets at depth) might be larger during winter than the flux of sinking fecal pellets.     

Microbial load from animal feces at a recreational beach

The goal of this study was to quantify the microbial load (enterococci) contributed by the different animals that frequent a beach site. The highest enterococci concentrations were observed in dog feces with average levels of 3.9 × 10⁷ CFU/g; the next highest enterococci levels were observed in birds averaging 3.3 × 10⁵ CFU/g. The lowest measured levels of enterococci were observed in material collected from shrimp fecal mounds (2.0 CFU/g). A comparison of the microbial loads showed that 1 dog fecal event was equivalent to 6940 bird fecal events or 3.2 × 10⁸ shrimp fecal mounds. Comparing animal contributions to previously published numbers for human bather shedding indicates that one adult human swimmer contributes approximately the same microbial load as one bird fecal event. Given the abundance of animals observed on the beach, this study suggests that dogs are the largest contributing animal source of enterococci to the beach site.     

Modern analogues and the early history of microbial life

Revealing the geological history of microbial life is very challenging. Microbes rarely are preserved with morphological fidelity, and even when they are, morphology is a poor guide to phylogeny and metabolism. Biological studies of environments considered analogous to those of paleobiological interest on the ancient Earth can inform interpretations and suggest new approaches. This paper reviews recent advances in our understanding of the biological diversity of two environments relevant to Archean paleobiology: those of extreme acidity and temperature (the Mt. Hood and White Island volcanoes), and high salinity (living stromatolites in Shark Bay). The combination of traditional microbial isolation with the use of modern molecular techniques has revealed that the microbial communities in these environments are much more diverse than originally thought. Through the extraction of whole microbial community DNA, enzymatic amplification of evolutionarily conserved genes, and cloning and sequencing of these genes, more specific and informed inferences concerning functional complexity in these extreme environments have now been made. Studies of the modern stromatolites have demonstrated that they have a very diverse range of micoorganisms, and contrary to previous interpretations, cyanobacteria are not the most abundant microbes present. In addition, many of the microorganisms are unique with no known close relatives, and these microorganisms may also possess novel physiologies vital to the integrity and persistence of stromatolites through space and time. Microbes in the volcanoes studied are present ubiquitously and include geochemically significant sulfur- and iron-cycling taxa. The findings from the studies reviewed here suggest that the Archean biota may have been functionally diverse and much more complex than has yet been revealed. The importance of studying modern analogues is stressed in that the biogeochemical processes occurring in these communities leave morphological, mineralogical, lipid and isotopic signals that could be sought in the rock record.     

Denaturing gradient gel electrophoresis shows that bacterial communities change with mid-ocean ballast water exchange

Ships carry ballast water for better stability and to control trim. However, the discharge of ballast water near ports is known to transport invasive species from one coastal area to another. The exchange of ballast water on the high seas is supposed to reduce such invasions of exotic species. In this study, we used denaturing gradient gel electrophoresis (DGGE) to analyze the composition of the bacterial community in ballast water before and after such a mid-ocean exchange, and we also measured total bacterial counts. Our findings confirmed that the ballast water was replaced by the mid-ocean exchange, as indicated by the marked change in the composition of the bacterial community. There was also a significant decrease in bacterial abundance after the mid-ocean exchange. Finally, our findings support the incubation hypothesis, because the composition of the bacterial communities changed over time within the same ballast water.