Heavy metals and TPH effects on microbial abundance and diversity in two estuarine areas of the southern-central coast of São Paulo State, Brazil

Collaborative effects of antimony-arsenic contaminations on microbial communities in the typical antimony mining areas of Southwest China

Antimony (Sb) and arsenic (As) co-contamination is prevalent in Sb mining areas and poses significant risks to the surrounding ecological environment. However, the extent of this co-contamination and the impact of key environmental variables and long-term exposure on the microbial communities remain poorly understood. Therefore, this study assessed Sb-As levels in three representative antimony mining areas in Southwest China and explored the relationships between microorganisms and environmental variables. The results indicated that the concentrations of soil Sb ranged from 6.90 to 50,794.07 mg/kg and As from 4.56 to 8798.86 mg/kg. The potential ecological risk index (RI) in mining and smelting areas surpassed 260, indicating a significantly high risk level. Sb-As predominantly exist as residual fractions. pH, electrical conductivity (EC), and interactions between Sb-As are critical factors influencing the transformation of their chemical fractions. Sb-As exposure altered the microbial community structure and diversity, with positive correlations dominating the co-network. Spearman correlation, redundancy analysis (RDA), canonical correspondence analysis (CCA), and random forest analysis (RF) indicated that the total concentration of Sb-As, the bioavailable fractions of Sb-As, pH, oxidation-reduction potential (Eh), and EC were the main variables affecting the microbial community. Variation partition analysis (VPA) indicated that Sb-As and their chemical fractions explained more microbial community variation than the physicochemical properties. Moreover, the bioavailable fractions were an even more significant variable influencing the microbial communities than the total concentrations of Sb-As. In-depth research on the ecological impact of Sb-As on microbial communities provides valuable insights for environmental monitoring and management.

Assessing spatial and temporal patterns of benthic bacterial communities in response to different sediment conditions

Benthic bacterial communities are sensitive to habitat condition and present a fast response to environmental stressors, which makes them powerful ecological indicators of estuarine environments. The aim of this work is to study the spatial-temporal patterns of benthic bacterial communities in response to contrasting environmental conditions and assess their potential as ecological indicators of estuarine sediments. We characterized the diversity of bacterial communities in three contrasting sites on Sado Estuary (SW Coast, Portugal) and 4 sampling occasions, using 16S metagenomic approach. Based on previous studies, we hypothesized that diversity patterns of bacterial communities will be distinct between sites and across sampling occasions. Bacterial communities were more influenced by each site conditions than by temporal variations in the sediments. The main drivers of bacterial distribution were sediments' composition, organic contents, and hydrodynamic activity. This work provided an important baseline dataset from Sado estuary to explore bacterial networks concerning benthic ecosystem functioning.

The occurrence and partition of total petroleum hydrocarbons in sediment, seawater, and biota of the eastern sea area of Shandong Peninsula, China

To investigate the occurrence and partition of total petroleum hydrocarbons (TPHs), sediment, seawater, and biota of the eastern sea area of Shandong Peninsula (China) were sampled in 2016. Due to shipping activities and discharge of industrial wastes, the TPH levels in the sediment decreased from the coastal areas to the offshore area. Waterborne TPH concentrations showed a decreasing order of autumn > summer > spring > winter, probably caused by low input of pollutants from the river into the ocean in dry seasons and frequent aquaculture operations in wet seasons. The distribution coefficient (logKd) between sediment and seawater ranged from 2.00 to 5.05, suggesting that TPHs are preferentially retained by the sediment. Significant positive correlations between logKd and total organic carbon (TOC), mud (fine particles), and temperature, as well as negative correlations between logKd and dissolved oxygen (DO), hydrogen ion concentration (pH), and oxidation-reduction potential (Eh), suggest interactions between environmental behaviors of TPHs and physicochemical factors. Mean bioaccumulation factors (BAFs) of TPHs in fish, shrimps, and mollusks were determined to be 240 ± 200, 900 ± 1800, and 2630 ± 1280, respectively, suggesting that considerable bioaccumulation occurs in shrimps when TPHs are transported from the seawater to the shrimps. A negative linear correlation between logTPHs and trophic level indicated biodilution of TPHs along the marine food web. This is the first study that has focused on the accumulation of TPHs in the entire sediment-seawater-biota system.

Effects of emerging contaminants and heavy metals on variation in bacterial communities in estuarine sediments

Emerging contaminants (ECs) and heavy metals (HMs) are universally present together in estuarine sediments; despite this, their effects on microbial communities have been widely studied separately, rather than in consort. In this study, the combined effects of ECs and HMs on microbial communities were investigated in sediments from 11 major river estuaries around the Bohai Sea, China. Proteobacteria, Bacteroidetes, and Firmicutes were the dominant phyla in the sediments. Using Shannon indices, total phosphorus and total organic carbon were shown to affect microbial community structure. Redundancy analysis of microbial variation implicated Cd and As as the greatest pollutants, followed by Mn, Fe, Zn and Cu; no impacts from galaxolide (HHCB) and tonalide (AHTN) were found. Correlation analysis demonstrated that the concentration of ECs increased the abundance of certain bacteria (e.g., Haliangium, Altererythrobacter, Gaiella and Erythrobacter), and therefore these can be used as potential contamination indicators. Shannon indices and Chao1 indices showed that there were differences in the richness and diversity of bacterial communities in the sediments of 11 rivers. The principal coordinate analysis displayed higher similarity of bacterial community composition in estuarine sediments in Liaoning province than other regions. The results can be used to predict changes in estuary ecosystems to maintain their ecological balance and health.

Effects of sediment physicochemical factors and heavy metals on the diversity, structure, and functions of bacterial and fungal communities from a eutrophic river

Urbanization has destroyed river ecosystems, leading to eutrophication. Heavy metals are frequently observed in urban rivers, and the joint effects of eutrophication and heavy metals on microbial communities, especially on fungal communities, have not been adequately explored. In this study, we explored the effect of sediment physicochemical factors and heavy metals on the microbial diversity, community structure, and functions of bacterial and fungal communities from a black-odorous river in Wuhu, China. Twenty-four samples were collected, and the diversity and structure of fungal and bacterial communities were determined by high-throughput sequencing. Proteobacteria and Rozellomycota were the main phyla in the bacterial and fungal communities, respectively. The results showed different distribution patterns of bacterial and fungal communities along the river. Physicochemical factors and heavy metals exhibited different effects on microbial variation. Specifically, pH and Cr negatively affected bacterial α-diversity, whereas total phosphorus and Cr significantly affected fungal α-diversity. Variance partitioning analysis revealed that physicochemical factors explained more of the bacterial community structure than heavy metals (49.5% vs. 36.6%), with pH and total phosphorus being the dominant factors. Opposite patterns were observed for fungal community structure, with heavy metals contributing the most (48.0%). A similar influence pattern was observed for the predicted functions of the two communities. This study suggests that heavy metals in eutrophication rivers are essential factors that shift the microbial variation and should be considered in urban river evaluation and remediation.

Effects of metals on activity and community of sulfate-reducing bacterial enrichments and the discovery of a new heavy metal-resistant SRB from Santos Port sediment (São Paulo, Brazil)

Sulfate-reducing bacteria (SRB) can be used to remove metals from wastewater, sewage, and contaminated areas. However, metals can be toxic to this group of bacteria. Sediments from port areas present abundance of SRB and also metal contamination. Their microbial community has been exposed to metals and can be a good inoculum for isolation of metal-resistant SRB. The objective of the study was to analyze how metals influence activity and composition of sulfate-reducing bacteria. Enrichment cultures were prepared with a different metal (Zn, Cr, Cu, and Cd) range concentration tracking activity of SRB and 16S rRNA sequencing in order to access the community. The SRB activity decreased when there was an increase in the concentration of the metals tested. The highest concentration of metals precipitated were 0.2 mM of Cd, 5.4 mM of Zn, 4.5 mM of Cu, and 9.6 mM of Cr. The more toxic metals were Cd and Cu and had a greater community similarity with less SRB and more fermenters (e.g., Citrobacter and Clostridium). Meanwhile, the enrichments with less toxic metals (Cr and Zn) had more sequences affiliated to SRB genera (mainly Desulfovibrio). A new Desulfovibrio species was isolated. This type of study can be useful to understand the effects of metals in SRB communities and help to optimize wastewater treatment processes contaminated by metals. The new Desulfovibrio species may be important in future studies on bioremediation of neutral pH effluents contaminated by metals.

Effects of heavy metals on microbial communities in sediments and establishment of bioindicators based on microbial taxa and function for environmental monitoring and management

Heavy metals have always been a research hotspot due to their persistence, hazard and bioaccumulation. Microorganisms are highly sensitive to heavy metal pollution and play an important role in the material cycling and energy flow of the ecosystem. In order to further explore the influence of heavy metals on the diversity, composition, and function of microbial communities in the wetland sediment ecosystem, and to find suitable indicators to reflect heavy metal pollution status, we collected sediments from Huangjinxia nature reserve and determined the physicochemical properties, heavy metal (Cu, Cr, Ni, Pb, Zn, and Mn) concentrations, and microbial information. We found that: the contamination status of the study area stood at a moderate level evaluated by the pollution load index (PLI); heavy metals explained more of microbial community variation than the sediment physicochemical properties; in particular, Cr and Mn negatively affected microbial α-diversity; heavy metals significantly affected the structure of microbial communities, elements Cr, Pb, and Zn showed uniformly negative associations with the relative abundance of bacteria Nitrospirae (including class Nitrospira and order Nitrospirales), Bacteroidetes (including class Bacteroidia), and Verrucomicrobia; moreover, heavy metals affected predicted functions of microbial communities, including metabolic functions, genetic information processes, and functions related to the carbon cycle and the nitrogen cycle. Based on the relative abundance of sensitive microbial taxa and predicted functions, bioindicators [Bacteroidia], 1/[Nitrospira], 1/[Nitrification], and 1/[Aerobic nitrite oxidation] were established to reflect and predict the contamination status of heavy metals in sediments. Our in-depth research on the effects of heavy metals on microorganisms and the establishment of bioindicators provide references and new perspectives for environmental monitoring and management.

Carbapenem resistant Enterobacteriaceae from port areas in São Paulo State (Brazil): Isolation and molecular characterization

Coastal areas with important economic activities have high levels of contamination by metals, pathogenic bacteria, among other contaminants. The emergence of antibiotic-resistant bacteria is a global problem of public health. Carbapenem resistant Enterobacteriaceae (CRE) are a serious threat. The occurrence of carbapenem resistant bacteria was investigated in waters and sediments of a Brazilian coastal area, characterized by high levels of contamination. The samples of water and sediment were collected in two areas of the coast of São Paulo (Brazil). The study involved the characterization of the molecular mechanisms associated with the carbapenem resistance phenotype. No genes were detected for β-lactamases but the absence and/or presence of mutations in outer membrane proteins (OMPs) may justify the detected phenotype. The presented results show the need for further studies that allow a review of the current legislation and the importance of the reevaluation of monitoring policies of these environments.

Heavy metal concentrations in Brazilian port areas and their relationships with microorganisms: can pollution in these areas change the microbial community?

The objectives of this study were to analyze the difference in ways in which metals polluting Brazilian port areas influence bacterial communities and the selection of resistant strains. The hypothesis tested was that port areas would have microbial communities significantly different from a pristine area, mainly due to a greater load of metals found in these areas. Sediment samples were collected in two port areas (Santos and São Sebastião) and one pristine area (Ubatuba). Total DNA was extracted and MiSeq sequencing was performed. A hundred strains were isolated from the same samples and were tested for metal resistance. The community composition was similar in the two port regions, but differed from the pristine area. Microbial diversity was significantly lower in the port areas. The phyla Proteobacteria, Cyanobacteria, and Thermodesulfobacteria exhibited positive correlations with copper and zinc concentrations. Chloroflex, Nitrospirae, Planctomycetes, and Chlorobi exhibited negative correlations with copper, chromium, and zinc. Cr and Zn had higher concentrations at port areas and were responsible to select more metal-resistant strains. Some genera were found to be able to easily develop metal resistance. The most isolated genera were Bacillus, Vibrio, and Pseudomonas. This type of study can illustrate, even in very complex natural environments, the influence of pollution on the community as a whole and the consequences of these changes.

Antibiotic contaminants reduced the treatment efficiency of UV-C on Microcystis aeruginosa through hormesis

Antibiotic contaminants exert stimulatory hormetic effects in cyanobacteria at low (ng L^-1) concentrations, which may interfere with the control of cyanobacterial bloom in aquatic environments exhibiting combined pollution. This study investigated the influence of a mixture of four popular antibiotics (sulfamethoxazole, amoxicillin, ciprofloxacin, and tetracycline) during the application of UV-C irradiation for controlling the bloom of Microcystis aeruginosa. In the absence of antibiotics, 100-500 mJ cm^-2 UV-C irradiation reduced cell density, growth rate, chlorophyll a content, F_v/F_m value and microcystin concentration in M. aeruginosa in a dose-dependent manner through the downregulation of proteins related to cell division, chlorophyll synthesis, photosynthesis and microcystin synthesis. UV-C irradiation stimulated microcystin release through the upregulation of the microcystin release regulatory protein (mcyH). The presence of 40 ng L^-1 antibiotic mixture during UV-C treatment significantly reduced (p < 0.05) the treatment efficiency of 100-300 mJ cm^-2 UV-C on microcystin concentration, while 80 and 160 ng L^-1 antibiotic mixture significantly reduced (p < 0.05) the treatment efficiency of 100-500 mJ cm^-2 UV-C on cell density and microcystin concentration. The antibiotic mixture alleviated the toxicity of UV-C on M. aeruginosa through a significant stimulation of photosynthetic activity (p < 0.05) and the upregulation of proteins involved in photosynthesis, biosynthesis, protein expression, and DNA repair. Microcystin release in UV-C-treated cyanobacterial cells was further stimulated by the antibiotic mixture through the upregulation of mcyH and four ATP-binding cassette transport proteins. The interference effects of antibiotic contaminants should be fully considered when UV-C is applied to control cyanobacterial bloom in antibiotic-polluted environments. In order to eliminate the interference effects of antibiotics, the concentration of each target antibiotic is suggested to be controlled below 5 ng L^-1 before the application of UV-C irradiation.

Response of sediment bacterial communities to the drainage of wastewater from aquaculture ponds in different seasons

Bacterial communities play an important role in diffuse sediment pollution in aquaculture farms. Previous studies have revealed the short-term influence of wastewater drainage on the bacterial communities but the seasonal response of the sediment bacterial communities to wastewater drainage from aquaculture farms remains unclear. This study used the 16S rRNA approach to explore the profiles of bacterial communities over four seasons in a typical crab aquaculture farm that included a pond and an outlet ditch. Nineteen sediment samples and an equal number of water samples were collected and analysed during spring, summer, autumn, and winter during 2018-19. Our results showed that Proteobacteria, Chloroflexi, and Bacteroides were the predominant phyla in aquaculture pond sediment with the relative abundance of 28.95%, 17.32%, and 15.31%, respectively. The relative abundance of Proteobacteria and Bacteroides was higher in autumn and winter, and the relative abundance of Chloroflexi was highest in spring. The Shannon diversity index value ranged from 6.17 to 9.30 and showed significant positive correlation (P < 0.01) with the concentrations of TN, NH₄⁺-N, and TP in the water. The variation in the bacterial community and relative abundance in outlet ditch sediment were consistent with those in the pond sediment. Our results show that determinisation of the bacterial community composition in the outlet ditch sediment provides a novel tool to monitor watersheds sensitive to the influence of aquacultures.

Adaptative responses of myenteric neurons of Sphoeroides testudineus to environmental pollution

Contamination in estuarine regions affects the local biota damaging the ecosystems and reaching humans. The gastrointestinal tract is a dynamic environment capable of obtaining nutrients and energy from food while it protects the host against harmful toxins and pathogens from the external environment. These functions are modulated by the enteric nervous system and changes in its structure can result in gastrointestinal disorders. The objective of this study was to evaluate if the environmental contaminants have effects on the myenteric neuronal plasticity of pufferfish Sphoeroides testudineus. Animals were collected in Barra do Una River, located at Jureia-Itatins Mosaic of Protected Areas (reference area - RA) and in the Santos Estuarine System (impacted area - IA). Morpho-quantitative analyses of the general and metabolically active myenteric neuronal populations of the proximal and distal intestine were made. Disarrangement was observed in the general organization of the myenteric plexus, with an expressive reduction of the neuronal groups (nodes) in the animals of IA. The vulnerability of the myenteric plexus was evidenced by a decrease in density and cellular profile of the general neuronal population, followed by an increase of the metabolism of the remaining neurons, which in turn was verified by a growth of the area of the cellular and nuclear profiles of the metabolically active neuronal population. Through these analyses, we concluded that animals inhabiting polluted regions present alterations in the myenteric neuronal plasticity, as a way of maintaining the functions of the gastrointestinal tract.

Comparative geochemical evaluation of toxic metals pollution and bacterial communities of industrial effluent tributary and a receiving estuary in Nigeria

Toxic metals/metalloid contaminations of estuarine sediments due to compromised tributaries arouse significant interest in studying bacterial community that triggers natural attenuation processes. Geo-accumulation index (I_geo), contamination factor (CF), pollution load index (PLI), and Hakanson potential ecological risk index (RI) as a sum of risk factors (Er) were used to quantify toxic metal/metalloid-pollution status of Lagos Lagoon (2W) and 'Iya-Alaro' tributary (4W) sediments in comparison with pristine 'Lekki Conservation Centre' sediment (L1-B). Bacteriology of the ecosystems was based on culture-independent analyses using pyrosequencing. 2W and 4W were extremely contaminated with mercury (I_geo > 7), whereas, cadmium contamination was only observed in 4W. The two ecosystems were polluted with toxic metal based on PLI, where mercury (Er = 2900 and 1900 for 4W and 2W, respectively) posed very high ecological risks. Molecular fingerprinting revealed that Proteobacteria, Firmicutes, and Acidobacteria predominately contributed the 20 most abundant genera in the two ecosystems. The 240 and 310 species present in 2W and 4W, respectively, but absent in L1-B, thrive under the metal concentrations in the polluted hydrosphere. Whereas, the 58,000 species missing in 2W and 4W but found in L1-B would serve as indicators for systems impacted with metal eco-toxicity. Despite toxic metal pollution of the ecosystems understudied, bacterial communities play vital roles in self-recovery processes occurring in the hydrosphere.

Response of freshwater sediment archaeal community to metal spill

Archaea play an important role in the biogeochemical cycling of elements in the environment. Heavy metals are ubiquitous pollutants in the environment. Previous studies have revealed a considerable influence of metal pollution on the archaeal community, but the short-term response of the archaeal community to metal pollution remains unclear. Hence, the present study investigated the short versus long-term responses of overall archaeal communities in freshwater sediments after exposure to accidental metal pollution caused by the discharge of heavy metal-containing wastewater from an indium-producing factory. Quantitative PCR was used to determine the archaeal abundance, while Illumina MiSeq sequencing was applied to characterize the diversity and structure of the archaeal community. The abundance (2.47 × 10⁵-1.55 × 10⁸ archaeal 16S rRNA gene copies per gram dry sediment), diversity (Shannon diversity index = 2.49-4.45) and structure of overall archaeal community illustrated a drastic temporal change. The archaeal communities mainly comprised the phyla Euryarchaeota, Thaumarchaeota and Bathyarchaeota. The exposure to metal pollution induced an increase in the proportion of Euryarchaeota but lowered the proportion of Thaumarchaeota. The accidental metal pollution exerted a profound impact on the archaeal community in freshwater sediment. This study could contribute our understanding of the short versus long-term response of archaeal communities to metal pollution.

Diversity and Distribution of Heavy Metal-Resistant Bacteria in Polluted Sediments of the Araça Bay, São Sebastião (SP), and the Relationship Between Heavy Metals and Organic Matter Concentrations

Heavy metals influence the population size, diversity, and metabolic activity of bacteria. In turn, bacteria can develop heavy metal resistance mechanisms, and this can be used in bioremediation of contaminated areas. The purpose of the present study was to understand how heavy metals concentration influence on diversity and distribution of heavy metal-resistant bacteria in Araça Bay, São Sebastião, on the São Paulo coast of Brazil. The hypothesis is that activities that contribute for heavy metal disposal and the increase of metals concentrations in environment can influence in density, diversity, and distribution of heavy metal-resistant bacteria. Only 12 % of the isolated bacteria were sensitive to all of the metals tested. We observed that the highest percentage of resistant strains were in areas closest to the São Sebastião channel, where port activity occurs and have bigger heavy metals concentrations. Bacterial isolated were most resistant to Cr, followed by Zn, Cd, and Cu. Few strains resisted to Cd levels greater than 200 mg L(-1). In respect to Cr, 36 % of the strains were able to grow in the presence of as much as 3200 mg L(-1). Few strains were able to grow at concentrations of Zn and Cu as high as 1600 mg L(-1), and none grew at the highest concentration of 3200 mg L(-1). Bacillus sp. was most frequently isolated and may be the dominant genus in heavy metal-polluted areas. Staphylococcus sp., Planococcus maritimus, and Vibrio aginolyticus were also isolated, suggesting their potential in bioremediation of contaminated sites.

Taxonomic profiling of bacterial community structure from coastal sediment of Alang-Sosiya shipbreaking yard near Bhavnagar, India

The Alang-Sosiya shipbreaking yard (ASSBY) is considered the largest of its kind in the world, and a major source of anthropogenic pollutants. The aim of this study was to investigate the impact of shipbreaking activities on the bacterial community structure with a combination of culture-dependent and culture-independent approaches. In the culture-dependent approach, 200 bacterial cultures were isolated and analyzed by molecular fingerprinting and 16S ribosomal RNA (r-RNA) gene sequencing, as well as being studied for degradation of polycyclic aromatic hydrocarbons (PAHs). In the culture-independent approach, operational taxonomic units (OTUs) were related to eight major phyla, of which Betaproteobacteria (especially Acidovorax) was predominantly found in the polluted sediments of ASSBY and Gammaproteobacteria in the pristine sediment sample. The statistical approaches showed a significant difference in the bacterial community structure between the pristine and polluted sediments. To the best of our knowledge, this is the first study investigating the effect of shipbreaking activity on the bacterial community structure of the coastal sediment at ASSBY.