Microbial ecology of a mercury -rich hot spring

Horizontal gene transfer (HGT) has been observed to occur between archaea and bacteria. The evolution of the mer operon which encodes for mercury resistance in microorganisms has been influenced by HGT. This study focuses on the microbial ecology of Coso Hot Springs (CHS) which contains high concentrations of mercuric sulfide or cinnabar. Specifically, this study was conducted to (a) identify archaeal and bacterial members of the CHS community, (b) determine whether HGT of merA genes occurred between the archaea and bacteria living in CHS and (c) determine the merA gene profile of microorganisms from CHS. Fluorescence in situ hybridization (FISH) analysis showed that the archaea made up 70% and the bacteria constituted 16% of the CHS microbial community. 16S rDNA sequencing identified the archaea in the pool to be Sulfolobus-like, Metallosphaera-like and Stygiolobus-like. Cultured archaea from CHS belonged to the genera Sulfolobus. The bacterial isolate belonged to a new species of Alicyclobacillus called Alicyclobacillus vulcanalis. A. vulcanalis has a temperature optima of 55°C, pH optima of 4.0, a %G+C content of 62 and possesses ω-cyclohexyl fatty acids as the major lipid component. Sequencing of the merA gene of A. vulcanalis showed that merA shared the closest identity to the merA genes of other Bacillus spp. and Gram+ bacteria. Sequence comparison of the merA genes of the archaeal and bacterial isolates from CHS revealed that HGT of merA did not occur between the two domains at CHS. A merA gene profile of uncultured archaea at CHS showed that there was very little diversity in the merA genes from CHS. This result could mean the predominance of a particular archaeal species selected for by the high mercury concentration and the yearly cycle of dehydration and rehydration that CHS undergoes. The results of this study will contribute to our understanding of the microorganisms that participate in global mercury cycling and provide baseline information that can aid in the formulation of strategies for bioremediation and mercury recovery

Assessment of the Effect of Remediation Strategies on the Environmental Quality of Aquaculture Ponds in Marilao and Meycauayan, Bulacan, Philippines

Background. Water quality in the Marilao-Meycauayan-Obando river system (MMORS) of Bulacan, the Philippines, is of great concern due to the pollution load from local industries. The river system is currently used as a source of water for the aquaculture industry in Bulacan. Objectives. In order to address organic and heavy metal pollution, several remediation strategies were tested in aquaculture ponds along the river system. Strategies such as phytoremediation (vetiver grass pontoons), application of probiotics and zeolite (with filtration as pre-treatment) were utilized in ponds to decrease or remove toxic pollutants in water and sediments. Methods. Two sites were chosen as the pilot remediation sites – ponds in Barangay Nagbalon, Marilao and Barangay Liputan, Meycauayan, Bulacan. Pond bottom preparation was done to improve the condition of the pond bottom sediments before stocking by adding zeolite. Physicochemical parameters of water such as dissolved oxygen (DO), temperature, pH, salinity, ammonia, phosphate, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) were monitored throughout the culture period. Heavy metals in sediments and fish were monitored. Fish parameters such as average body weight and feed conversion ratio were determined. Results. The DO levels were below recommended levels in the morning and reached a supersaturated level in the afternoon. Ammonia and COD levels were above recommended limits. A decreasing trend was observed for ammonia levels in treatment ponds. In terms of the growth of milkfish, the pond with probiotics showed the highest growth and better feed conversion ratio in Nagbalon and in the phytoremediation pond in Liputan. Percentage survival of milkfish was much higher at Liputan. Copper, chromium, lead and manganese were detected in pond sediments. After application of zeolite, there was a decrease in lead levels throughout the culture period. Conclusions. The different remediation studies were compared in terms of cost, effectivity and application and phytoremediation (vetiver grass pontoons) was determined to be the most cost-effective remediation strategy. Competing Interests. The authors declare no competing financial interests

Physico-Chemical Quality and Physiological Profiles of Microbial Communities in Freshwater Systems of Mega Manila, Philippines

Studying the quality of freshwater systems and drinking water in highly urbanized megalopolises around the world remains a challenge. This article reports data on the quality of select freshwater systems in Mega Manila, Philippines. Water samples collected between 2020 and 2021 were analyzed for physico-chemical parameters and microbial community metabolic fingerprints, i.e., carbon substrate utilization patterns (CSUPs). The detection of arsenic, lead, cadmium, mercury, polyaromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs) was carried out using standard chromatography- and spectroscopy-based protocols. Physiological profiles were determined using the Biolog EcoPlate™ system. Eight samples were free of heavy metals, and none contained PAHs or OCPs. Fourteen samples had high microbial activity, as indicated by average well color development (AWCD) and community metabolic diversity (CMD) values. Community-level physiological profiling (CLPP) revealed that (1) samples clustered as groups according to shared CSUPs, and (2) microbial communities in non-drinking samples actively utilized all six substrate classes compared to drinking samples. The data reported here can provide a baseline or a comparator for prospective quality assessments of drinking water and freshwater sources in the region. Metabolic fingerprinting using CSUPs is a simple and cheap phenotypic analysis of microbial communities and their physiological activity in aquatic environments