Molecular Adaptations of Bacterial Mercuric Reductase to the Hypersaline Kebrit Deep in the Red Sea

Metagenomic profiling of antibiotic resistance genes in Red Sea brine pools

Antibiotic resistance (AR) is an alarming global health concern, causing an annual death rate of more than 35,000 deaths in the US. AR is a natural phenomenon, reported in several pristine environments. In this study, we report AR in pristine Red Sea deep brine pools. Antimicrobial resistance genes (ARGs) were detected for several drug classes with tetracycline and macrolide resistance being the most abundant. As expected, ARGs abundance increased in accordance with the level of human impact with pristine Red Sea samples having the lowest mean ARG level followed by estuary samples, while activated sludge samples showed a significantly higher ARG level. ARG hierarchical clustering grouped drug classes for which resistance was detected in Atlantis II Deep brine pool independent of the rest of the samples. ARG abundance was significantly lower in the Discovery Deep brine pool. A correlation between integrons and ARGs abundance in brine pristine samples could be detected, while insertion sequences and plasmids showed a correlation with ARGs abundance in human-impacted samples not seen in brine pristine samples. This suggests different roles of distinct mobile genetic elements (MGEs) in ARG distribution in pristine versus human-impacted sites. Additionally, we showed the presence of mobile antibiotic resistance genes in the Atlantis II brine pool as evidenced by the co-existence of integrases and plasmid replication proteins on the same contigs harboring predicted multidrug-resistant efflux pumps. This study addresses the role of non-pathogenic environmental bacteria as a silent reservoir for ARGs, and the possible horizontal gene transfer mechanism mediating ARG acquisition.

A review on algal-bacterial symbiosis system for aquaculture tail water treatment

Aquaculture is one of the fastest growing fields of global food production industry in recent years. To maintain the ecological health of aquaculture water body and the sustainable development of aquaculture industry, the treatment of aquaculture tail water (ATW) is becoming an indispensable task. This paper discussed the demand of environmentally friendly and cost-effective technologies for ATW treatment and the potential of algal-bacterial symbiosis system (ABSS) in ATW treatment. The characteristics of ABSS based technology for ATW treatment were analyzed, such as energy consumption, greenhouse gas emission, environmental adaptability and the possibility of removal or recovery of carbon, nitrogen and phosphorus as resource simultaneously. Based on the principle of ABSS, this paper introduced the key environmental factors that should be paid attention to in the establishment of ABSS, and then summarized the species of algae, bacteria and the proportion of algae and bacteria commonly used in the establishment of ABSS. Finally, the reactor technologies and the relevant research gaps in the establishment of ABSS were reviewed and discussed.

Comparative 16S Metabarcoding of Nile Tilapia Gut Microbiota from the Northern Lakes of Egypt

Nile tilapia, Oreochromis niloticus, is the principal fish bred in Egypt. A pilot study was designed to analyze the bacterial composition of the Nile tilapia fish guts from two saltwater lakes in Northern Egypt. Fish samples were obtained from two Delta lakes: Manzala (ML) and Borollus (BL). DNA was extracted, and the bacterial communities in the stomach content were classified (down to the species level) using the 16S rRNA-based analysis. From the two metagenomics libraries in this study, 1,426,740 reads of the amplicon sequence corresponding to 508 total taxonomic operational units were recorded. The most prevalent bacterial phyla were Proteobacteria, Firmicutes, Actinobacteria, and Synergistetes in all samples. Some of the strains identified belong to classes of pathogenic zoonotic bacteria. A notable difference was observed between gut bacteria of Nile tilapia fish obtained from BL and ML. There is a remarkable indication that Nile tilapia fish living in BL is heavily burdened with pathogenic microbes most remarkably those involved with methylation of mercury and its accumulation in fish organs. These pathogenic microbes could have clinical implications and correlated with many diseases. This result was also consistent with the metagenomic data's functional prediction that indicated that Nile tilapia species harboring these two Egyptian northern lakes may be exposed to numerous anthropogenic pollutants. The findings show that the host environment has a significant impact on the composition of its microbiota. The first step towards exploring the better management of this profit-making fish is recognizing the structure of the microbiome.

Novel Enzymes From the Red Sea Brine Pools: Current State and Potential

The Red Sea is a marine environment with unique chemical characteristics and physical topographies. Among the various habitats offered by the Red Sea, the deep-sea brine pools are the most extreme in terms of salinity, temperature and metal contents. Nonetheless, the brine pools host rich polyextremophilic bacterial and archaeal communities. These microbial communities are promising sources for various classes of enzymes adapted to harsh environments - extremozymes. Extremozymes are emerging as novel biocatalysts for biotechnological applications due to their ability to perform catalytic reactions under harsh biophysical conditions, such as those used in many industrial processes. In this review, we provide an overview of the extremozymes from different Red Sea brine pools and discuss the overall biotechnological potential of the Red Sea proteome.

Effect of salinity and algae biomass on mercury cycling genes and bacterial communities in sediments under mercury contamination: Implications of the mercury cycle in arid regions

Lakes in arid regions are experiencing mercury pollution via air deposition and surface runoff, posing a threat to ecosystem safety and human health. Furthermore, salinity and organic matter input could influence the mercury cycle and composition of bacterial communities in the sediment. In this study, the effects of salinity and algae biomass as an important organic matter on the genes (merA and hgcA) involved in the mercury cycle under mercury contamination were investigated. Archaeal merA and hgcA were not detected in sediments of lake microcosms, indicating that bacteria rather than archaea played a crucial role in mercury reduction and methylation. The high content of mercury (300 ng g^-1) could reduce the abundance of both merA and hgcA. The effects of salinity and algae biomass on mercury cycling genes depended on the gene type and dose. A higher input of algae biomass (250 mg L^-1) led to an increase of merA abundance, but a decrease of hgcA abundance. All high inputs of mercury, salinity, and algae biomass decreased the richness and diversity of bacterial communities in sediment. Further analysis indicated that higher mercury (300 ng g^-1) led to an increased relative abundance of mercury methylators, such as Ruminococcaceae, Bacteroidaceae, and Veillonellaceae. Under saline conditions (10 and 30 g L^-1), the richness of specific bacteria associated with mercury reduction (Halomonadaceae) and methylation (Syntrophomonadaceae) increased compared to the control. The input of algae biomass led to an increase in the specific bacterial communities associated with the mercury cycle and the richness of bacteria involved in the decomposition of organic matter. These results provide insight into mercury cycle-related genes and bacterial communities in the sediments of lakes in arid regions.