P.M. Manage

Isolation and identification of novel microcystin-degrading bacteria.

ABSTRACT Of 31 freshwater bacterial isolates screened using the Biolog MT2 assay to determine their metabolism of the microcystin LR, 10 were positive. Phylogenetic analysis (16S rRNA) identified them as Arthrobacter spp., Brevibacterium sp., and Rhodococcus sp. This is the first report of microcystin degraders that do not belong to the Proteobacteria.

Species-specific concentrations of perfluoroalkyl contaminants in farm and pet animals in Japan

The persistent metabolites of perfluorinated compounds (PFCs) which have been detected in the tissues of both humans and wildlife, and human contamination by PFCs suggest differences in the exposure patterns to these compounds. However, studies focused on identifying human exposure pathways to PFCs are scarce. To provide a preliminary assessment of PFCs in farm animals such as chicken, cattle, pigs, goats and horses, blood and liver samples were collected from various regions in Japan. Additionally, dog sera samples representing pet animals were also employed for analysis. Perfluorooctane sulfonate (PFOS) was the most prominent contaminant found in farm and pet animals, with mean sera PFOS concentrations (in decreasing order) of: chicken (5.8 ng/ml)>cattle (3.0 ng/ml)>goat (2.4 ng/ml)>horse (0.71 ng/ml)>pig (0.37 ng/ml). Chicken livers (67 ng/g) contained the highest mean PFOS concentration among the farm animals, followed by those of pigs (54 ng/g) and cattle (34 ng/g). In comparison to PFOS levels in farm animals, the detected levels of other PFCs were not significant. The high levels of PFOS found in cattle fetal livers suggest that PFOS crosses the placental barrier to enter fetal circulation. The consumption of chicken by humans might produce higher PFOS exposure in humans compared to that in farm animals; however, the current levels of PFOS in farm animals in Japan were lower than those reported in fish and wild animals. Elevated concentrations of both PFOS (25 ng/ml) and perfluorohexane sulfonate (PFHxS; 10 ng/ml) were found in dog sera, indicating that further studies are needed to identify PFC sources in the human environment.

Novel bacterial strains for the removal of microcystins from drinking water

Microcystins (MC) and nodularin (NOD) are common contaminants of drinking water around the world and due to their significant health impact it is important to explore suitable approaches for their removal. Unfortunately, these toxins are not always removed by conventional water treatments. One of the most exciting areas that hold promise for a successful and cost effective solution is bioremediation of microcystins. Recent work resulted in successful isolation and characterisation of 10 novel bacterial strains (Rhodococcus sp., Arthrobacter spp. and Brevibacterium sp.) capable of metabolizing microcystin-LR (MC-LR) in a Biolog MT2 assay. The work presented here aims to further investigate and evaluate the metabolism and the degradation of multiple microcystins (MC-LR, MC-LF, MC-LY, MC-LW and MC-RR) and nodularin by the bacterial isolates. A total of five bacterial isolates representing the three genera were evaluated using Biolog MT2 assay with a range of MCs where they all demonstrated an overall metabolism on all MCs and NOD. Subsequently, the results were confirmed by observing the degradation of the range of toxins in a separate batch experiment.

Decolorization of CI Direct Blue 201 Textile Dye by Native Bacteria

Water pollution from untreated or partially treated textile dye effluents is one of the major problem concerns globally. Synthetic dyes extensively are used for textile dyeing process. They are highly recalcitrant to natural decolorization and degradation processes and will create drastic negative impacts on natural environment. Remediation of synthetic textile dyes through biological agents has been recorded as low cost and environmental friendly alternative for expensive chemical and physical treatment methods. Therefore the present study was aimed on the determination of CI Direct Blue 201 textile dye decolorizing ability by isolated bacteria strains. Among the 35 bacteria strains isolated from effluents of textile industries, five bacteria strains have shown remarkable decolorizing abilities on CI Direct Blue textile dye. The isolated bacteria were tentatively identified as Pseudomonas sp.1, Pseudomonas sp.2, Bacillus sp.1, Bacillus sp.2 and Micrococcus sp. by morphological features and biochemical tests. Decolorization kinetics of bacteria was recorded after 14 days of incubation with CI Direct Blue 201 dye treated at 75 ppm. Descending order of dye decolorization was resulted by Pseudomonas sp.2 (58.15 ± 0.92%), Bacillus sp.2 (55.02 ± 0.70%), Pseudomonas sp.1 (54.73 ± 1.99%), Micrococcus sp. (51.86 ± 0.49%) and Bacillus sp. 1 (51.55 ± 0.74%) at 280C respectively. Descending decolorization potential was shown by all bacteria as a response for the ascending initial concentration of dye. The highest decolorization of dye was recorded by Pseudomonas sp.2 as 67.93 ± 1.23% at 50 ppm. High decolorization percentages were obtained when bacteria were incubated at 320C compared to 280C and 240C. Results of the present study revealed that isolated bacteria will be successful aspirants for remediation of synthetic textile dyes as an ecofriendly bioremediators to consider for green application approaches. However further studies are needed to understand their dye degradation mechanism in natural environment.

Isolation and characterisation of oil degrading bacteria from coastal waters and sediments from three locations in Sri Lanka

Microbial degradation of petroleum hydrocarbons is one of the important pathways in the natural decomposition process. Four potential oil degrading bacteria were isolated from the coastal waters and sediments in Sri Lanka and identified as Bacillus cereus, Enterobacter sp., Enterobacter ulcerans and Micrococcus sp. by 16S rRNA sequencing. The highest degradation percentage of crude oil was detected at 14 days of incubation by B. cereus (84 %). The remaining strains of Enterobacter sp. (80 %), Micrococcus sp. (74 %) and E. ulcerans (74 %) were also detected as active degraders. The lowest half life time was recorded for Enterobacter sp. at 6 days of incubation, while the half life time of B. cereus and Micrococcus sp. was 7 days, and 10 days for E. ulcerans . The population densities of bacteria were proportional to their degradation rates. Different emulsification index values were detected starting from 18 ‒ 65 % for B. cereus , 48 % for Enterobacter sp., 38 % for Micrococcus sp., and 38 % for E. ulcerans at 14 days of incubation. The FTIR spectrum analysis revealed that the peak area relevant to the C-H groupʼs stretching (2850 ‒ 3000 cm-1) decreased with incubation from 0.115 to 0.04 for B. cereus and from 0.115 to 0.08 for Enterobacter sp.. The infrared absorption wavelength range of 1455 ‒ 1500 cm-1 relevant to deformations of C-H bonds to CH2, CH3, and cyclohexanes decreased from 0.08 to 0.018 in B. cereus and from 0.08 to 0.04 for Enterobacter sp.. Among the bacterial isolates B. cereus was identified as the most efficient hydrocarbon degrader in the present study.

Toxin Producing Cyanobacteria in Labugama, Kalatuwawa Drinking Water Reservoirs

Cyanobacteria are photosynthetic bacteria found naturally in lakes, streams, ponds, and reservoirs. Microcystis aeruginosa, Anabaena sp., Nostoc sp., Oscillatoria sp. are some harmful cyanobacteria that produce cyanotoxins. Microcystin-LR (MC-LR) is the dominant type of cyanotoxin produced by these cyanobacteria. MC-LR causes hepatotoxic effect on human beings and are harmful to animals as well. Therefore, World Health Organisation (WHO) has recommended a guideline value of less than 1 μg/l of MC-LR should be present in drinking water. The present study assesed the presence of toxin producing cyanobacteria and quantifies MC-LR in Labugama and Kalatuwawa drinking water reservoirs, from June to December 2014. Water samples were collected from five sampling locations of both water bodies and plankton samples were collected using 55 μm plankton net. Filtered water samples were fixed in acidified lugols‟ solution at a final concentration of 1%. Following natural sedimentation, identification of cyanobacteria was carried out. Quantification of MCLR was done using photodiode array-high pressure liquid chromatography method (PDAHPLC). M. aeruginosa (54.6±0.17%) was the dominant cyanobacteria whereas Pediastrum duplex (30.4±1.89%), Coelastrum sp. (12±0.19%) and Ankistrodesmus sp. (3±0.02%) were the non-toxic algae strains present in Labugama reservoir. M. aeruginosa (68.2±0.09%) and Anabaena sp. (16.2±0.12%) were the toxic cyanobacteria present in Kalatuwawa reservoir whereas P. duplex (7.3±0.08%), Coelastrum sp. (5.6±0.24%), Staurastrum sp. (1.2±0.05%) and Scenedesmus sp. (1.5±0.004%) were found as non-toxic algae species. MC-LR concentration of Labugama and Kalatuwawa reservoirs ranged between 0-1.27±0.04 μg/ml and 0.76±0.001-1.45±0.02 μg/ml respectively. Based on the results of the present study, both reservoirs were contaminated with MC-LR and responsible cyanobacteria strains would be M. aeruginosa and Anabaena sp. Thus, continuous monitoring is essential in order to assess the suitability of these two water bodies for human drinking purpose. Keywords: Cyanobacteria, Microcystis. aeruginosa, MC-LR, Drinking water, PDA-HPLC

Removal of Amoxicillin and Sulfanomide by Freshwater Bacteria in Sri Lanka

Antibiotics are an important group of pharmaceuticals used in human and animal health care. Most of the antibiotics are prone to release to the environment due to improper usage. This has resulted in bacterial resistance development and toxicity in aquatic communities. Present study reports the biodegradation of amoxicillin (AMX) and sulfanomide (SUF) by Bacillus cereus, Enterobacter ludwigii and Enterobacter sp. strains which were previously reported as crude oil degraders. Different concentrations of AMX and SUF (0, 60, 120, 180, 240, 300, 360, 420 ppm) were used to detect minimum inhibition concentration (MIC) by standard pour plate method. AMX and SUF degradation kinetics were studied by introducing 0.5 ml of overnight starved bacterial suspensions into sterile antibiotic medium in triplicate at final concentration of 60 and 120 ppm respectively. The samples were incubated at 280 C shaking at 100 rpm and 0.5 ml sub-sample aliquots were removed at two days interval for a period of 14 days. Analyses of antibiotics were performed by high performance liquid chromatography (HPLC). The MIC values for SUF and AMX were detected as 240, 420 ppm for B. cereus, 120, 360 ppm for E. ludwigii and 180 and 300 ppm for Enterococcus sp. respectively. After 14 days of incubation complete removal of AMX and 80% degradation of SUF was recorded by bacterium B. cereus. E. ludwigii showed 75% degradation of AMX and 60% degradation of SUF where Enterobacter sp. showed degradation of both AMX (80%) and SUF (70%) respectively. Thus, the present study illustrate antibiotics degradation potential of microbial community is important to understand their role in removal of antibiotics from the natural environment. Keywords: Biodegradation, Minimum Inhibitory Concentrations (MICs), Amoxicillin, Sulfanomide, Bacillus cereus, Enterobacter ludwigii, Enterobacter sp.