Millimeter-scale vertical partitioning of nitrogen cycling in hypersaline mats reveals prominence of genes encoding multi-heme and prismane proteins

Insights into the impact of 6PPD-Q and 6PPD on nitrogen metabolism and microbial community in the anammox system

N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is an antioxidant commonly used in tire manufacturing, and its release into the environment has significantly increased due to rapid urbanization. When subjected to ozonation, 6PPD converts into the harmful pollutant 6PPD quinone (6PPDQ). These substances enter wastewater treatment plants (WWTPs) via stormwater runoff and pipelines, posing significant risks to the functional microorganisms. Anammox, a strictly controlled and sensitive microbial nitrogen removal process, is especially susceptible to the effects of the pollutants. This study investigates the comprehensive impact of 6PPD-Q and 6PPD on anammox communities based on characterization analysis and metagenomics. At environmental concentrations, 6PPD-Q at 200 ng/L-1000 ng/L led to the disintegration of anammox granules. Extended exposure to both 6PPD-Q and 6PPD significantly reduces the population of anammox bacteria (AnAOB). By utilizing organic matter from dead cells and incoming carbonate as a carbon source, the system evolved into a nitrogen metabolism network primarily focused on denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This transformation was accompanied by a reshuffling of the microbial community and associated genes, resulting in an accumulation of NH4+-N. These findings underscore the toxicity of 6PPD-Q and 6PPD to anammox and stress the importance of incorporating 6PPD into regulatory and preventive strategies.

Prokaryotic morphological features and maintenance activities governed by seasonal productivity conditions

Prokaryotic maintenance respiration and associated metabolic activities constitute a considerable proportion of the total respiration of carbon to CO2 in the ocean's mixed layer. However, seasonal influences on prokaryotic maintenance activities in terms of morphological and metabolic adaptations at low (winter) and high productivity (summer) are still unclear. To address this, we examined the natural prokaryotic communities at the mesocosm scale to analyse the differences in their morphological features and gene expression at low and high maintenance respiration, experimentally manipulated with the specific growth rate. Here, we showed that morphological features including membrane blebbing, membrane vesicles, and cell‒cell connections occurred under high productivity. Metabolic adaptations associated with maintenance activities were observed under low productivity. Several Kyoto Encyclopedia of Genes and Genomes categories related to signal transduction, energy metabolism, and translational machinery supported maintenance activities under simulated winter conditions. Differential abundances of genes related to transporters, osmoregulation, nitrogen metabolism, ribosome biogenesis, and cold stress were observed. Our results demonstrate how specific growth rate in different seasons can influence resource allocation at the levels of morphological features and metabolic adaptations. This motivates further study of morphological features and their ecological role during high productivity, while investigations of metabolic adaptations during low productivity can advance our knowledge about maintenance activities.

Metatranscriptomic profiles reveal the biotransformation potential of azithromycin in river periphyton

Assessment of the interaction between the biotransformation of chemical contaminants and enzyme activity from aquatic microbial communities is critical for improving the micropollutant degradation in river remediation. Here, association mining based on metatranscriptomic analysis was initially applied to determine the genes encoding enzymes involved in the azithromycin (AZI) transformation process and the corresponding microbial hosts in periphyton, followed by revealing the dynamic variation in the community structure and function. In terms of the biotransformation potential, the highly correlated 15 enzymes were suggested to be primarily involved in AZI biotransformation, energy supply, and antibiotic resistance processes, especially aryl-alcohol dehydrogenases (EC: 1.1.1.90), hydroxylamine dehydrogenase (EC: 1.7.2.6), and monooxygenases (EC: 1.14.11.57) that were involved in the biotransformation of AZI. In the matter of community ecological function, the photosystem II (PSII) reaction center in the periphytic photosynthetic process, as indicated by Fv/Fm, was inhibited after AZI exposure, which may be attributed to the down-regulated genes enriched in the photosynthesis - antenna proteins (ko00196), photosynthesis (ko00195), and two-component system (ko02020) pathways. Furthermore, the periphytic utilization capacity for carbohydrates and phenolic acids was enhanced, which was in accordance with all the increased expression of transcripts involved in the corresponding molecular pathways, including aminobenzoate degradation (ko00627), starch and sucrose metabolism (ko00500), ABC transporters (ko02010), phosphotransferase system (ko02060), galactose metabolism (ko00052), amino sugar and nucleotide sugar metabolism (ko00520). Taken together, this study highlighted the critical role of river periphyton in the micropollutant degradation and unraveled the molecular mechanism of antibiotic biotransformation as well as the structural and functional damage in the periphyton.

Community ecology and functional potential of bacteria, archaea, eukarya and viruses in Guerrero Negro microbial mat

In this study, the microbial ecology, potential environmental adaptive mechanisms, and the potential evolutionary interlinking of genes between bacterial, archaeal and viral lineages in Guerrero Negro (GN) microbial mat were investigated using metagenomic sequencing across a vertical transect at millimeter scale. The community composition based on unique genes comprised bacteria (98.01%), archaea (1.81%), eukarya (0.07%) and viruses (0.11%). A gene-focused analysis of bacteria archaea, eukarya and viruses showed a vertical partition of the community. The greatest coverages of genes of bacteria and eukarya were detected in first layers, while the highest coverages of genes of archaea and viruses were found in deeper layers. Many genes potentially related to adaptation to the local environment were detected, such as UV radiation, multidrug resistance, oxidative stress, heavy metals, salinity and desiccation. Those genes were found in bacterial, archaeal and viral lineages with 6477, 44, and 1 genes, respectively. The evolutionary histories of those genes were studied using phylogenetic analysis, showing an interlinking between domains in GN mat.

Performance changes in the anammox process under the stress of rare-earth element Ce(III) and the evolution of microbial community and functional genes

The high Ce(III) content in ionic rare-earth tailings wastewater has hindered the application of anammox process in this field. Here, the effect of Ce(III) on the performance of anammox processes was investigated, and the evolution of microbial communities and functional genes was explored using metagenomic sequencing. The results showed that the reactor nitrogen removal rate decreased when the Ce(III) concentration reached 25 mg/L, although ammonia nitrogen removal (92.31%) and nitrogen removal efficiency (81.33%) remained at a high level; however, both showed a significant decreasing trend. The relative abundance of anammox bacteria increased continuously from P1-P5, reaching 48.81%, whereas the relative abundance of Candidatus jettenia reached 33.71% at P5, which surpassed that of Candidatus brocadia as the most abundant anammox bacteria, and further analysis of functional genes and metabolic pathways revealed that Candidatus brocadia was richer in biochemical metabolic genes, whereas Candidatus jettenia had richer efflux genes.

Identification of Antibacterial Components and Modes in the Methanol-Phase Extract from a Herbal Plant Potentilla kleiniana Wight et Arn

The increase in bacterial resistance and the decline in the effectiveness of antimicrobial agents are challenging issues for the control of infectious diseases. Traditional Chinese herbal plants are potential sources of new or alternative medicine. Here, we identified antimicrobial components and action modes of the methanol-phase extract from an edible herb Potentilla kleiniana Wight et Arn, which had a 68.18% inhibition rate against 22 species of common pathogenic bacteria. The extract was purified using preparative high-performance liquid chromatography (Prep-HPLC), and three separated fragments (Fragments 1-3) were obtained. Fragment 1 significantly elevated cell surface hydrophobicity and membrane permeability but reduced membrane fluidity, disrupting the cell integrity of the Gram-negative and Gram-positive pathogens tested (p < 0.05). Sixty-six compounds in Fragment 1 were identified using Ultra-HPLC and mass spectrometry (UHPLC-MS). The identified oxymorphone (6.29%) and rutin (6.29%) were predominant in Fragment 1. Multiple cellular metabolic pathways were altered by Fragment 1, such as the repressed ABC transporters, protein translation, and energy supply in two representative Gram-negative and Gram-positive strains (p < 0.05). Overall, this study demonstrates that Fragment 1 from P. kleiniana Wight et Arn is a promising candidate for antibacterial medicine and food preservatives.