Responses of bacterial communities in seagrass sediments to polycyclic aromatic hydrocarbon-induced stress

Adaptation strategies and functional transitions of microbial community in pyrene-contaminated soils promoted by lead with Pseudomonas veronii and its extracellular polymeric substances

Pyrene was designated as a remediation target in this study, and low contamination of lead (Pb) was set to induce heavy metal stress. Pseudomonas veronii and its extracellular polymeric substances (EPSs) were chosen for biofortification, with the aim of elucidating the structural, metabolic, and functional responses of soil microbial communities. Community analysis of soil microorganisms using high-throughput sequencing showed that the co-addition of P. veronii and EPSs resulted in an increase in relative abundance of phyla associated with pyrene degradation, and formed a symbiotic system dominated by Firmicutes and Proteobacteria, which involved in pyrene metabolism. Co-occurrence network analysis revealed that the module containing P. veronii was the only one exhibiting a positive correlation between bacterial abundance and pyrene removal, indicating the potential of bioaugmentation in enriching functional taxa. Biofortification also enhanced the abundance of functional gene linked to EPS production (biofilm formation-Pseudomonas aeruginosa) and pyrene degradation. Furthermore, 17 potential functional bacteria were screened out using random forest algorithm. Lead contamination further promoted the growth of Proteobacteria, intensified cooperative associations among bacteria, and increased the abundance of bacteria with positive correlation with pyrene degradation. The results offer novel perspectives on alterations in microbial communities resulting from the synergistic impact of heavy metal stress and biofortification.

Effects of different colored polyethylene mulching films on bacterial communities from soil during enrichment incubation

Studies have shown that mulching agricultural fields with plastic residues can influence microbial communities in the environment, but few studies have investigated the differences in the soil microbial communities in distinct areas under mulching with different colored plastic products. Thus, in this study, we explored how different colored polyethylene mulching films (PMFs) might affect soil bacterial communities during enrichment incubation. We found significant differences in the bacterial communities under different colored PMFs after incubation. Treatment with the same colored PMF obtained more similar bacterial community compositions. For instance, at the class level, Gammaproteobacteria and Bacteroidia were most abundant with black PMF, whereas Actinobacteria and Bacteroidia were most abundant with white PMF. The most abundant genera were Acinetobacter and Chryseobacterium with black PMF but Rhodanobacter and Paenarthrobacter with white PMF. Polyethylene- and hydrocarbon-degrading bacteria were the core members detected under both treatments, and the bacterial communities were predicted to have the potential for the biodegradation and metabolism of xenobiotics after enrichment culture according to the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) tool. In addition, the bacterial communities in soil from Xinjiang treated with white PMF and in soil from Yangling treated with black PMF were strongly correlated and stable. Our results suggest that the color of the PMF applied affected the soil bacterial communities, where plastics with the same color may have recruited similar species of microorganisms, although the origins of these microorganisms were not the same.

Impacts of bio-stimulants on pyrene degradation, prokaryotic community compositions, and functions

Bio-stimulation of the indigenous microbial community is considered as an effective strategy for the bioremediation of polluted environments. This examination explored the near effects of various bio-stimulants on pyrene degradation, prokaryotic community compositions, and functions using 16S rRNA amplicon sequencing and qPCR. At first, the results displayed significant differences (p < 0.05) between the prokaryotic community structures of the control group, PYR (contains pyrene only), and bio-stimulants amended groups. Among the bio-stimulants, biochar, oxalic acid, salicylate, NPK, and ammonium sulfate augmented the pyrene degradation potential of microbial communities. Moreover, the higher abundance of genera, such as Flavobacterium, Hydrogenophaga, Mycobacterium, Rhodococcus, Flavihumibacter, Pseudomonas, Novosphingobium, etc., across the treatments indicated that these genera play a vital role in pyrene metabolism. Based on the higher abundance of GP-RHD and nidA genes, we speculated that Gram-positive prokaryotic communities are more competent in pyrene dissipation than Gram-negative. Furthermore, the marked abundance of nifH, and pqqC genes in the NPK and SA treatments, respectively, suggested that different bio-stimulants might enrich certain bacterial assemblages. Besides, the significant distinctions (p < 0.05) between the bacterial consortia of HA (humic acid) and SA (sodium acetate) groups from NPK, OX (oxalic acid), UR (urea), NH4, and SC (salicylate) groups also suggested that different bio-stimulants might induce distinct ecological impacts influencing the succession of prokaryotic communities in distinct directions. This work provides new insight into the bacterial degradation of pyrene using the bio-stimulation technique. It suggests that it is equally important to investigate the community structure and functions along with studying their impacts on degradation when devising a bio-stimulation technology.

Composition and Functional Characteristics and Influencing Factors of Bacterioplankton Community in the Huangshui River, China

Bacterial community plays a key role in environmental and ecological processes of river ecosystems. Given the special climatic and geographical conditions, studying the compositional characteristics of microorganisms in highland rivers and the relationship between such microorganisms and water physicochemical factors is important for an in-depth understanding of microbial ecological mechanisms. In the present study, high-throughput sequencing was used to investigate and study the bacterioplankton community of the Huangshui River in the ecotone zone of the Qinghai Plateau and Loess Plateau. The results showed that the Huangshui River had significantly lower alpha diversity than the plain rivers. Despite the similarity in their environmental conditions, the main taxonomic compositions of the bacterial communities were distinct between the Huangshui River and polar regions (the Arctic and Antarctica). Proteobacteria accounted for the largest proportion (30.79–99.98%) of all the sequences, followed by Firmicutes (0–49.38%). Acidiphilium was the most numerous genera, which accounted for 0.03–86.16% of the assigned 16S reads, followed by Acidocella (0–95.9%), both belonging to Alphaproteobacteria. The diverse taxa of potential pathogens, such as Acinetobacter, Pseudomonas, and Aeromonas, were also identified. A principal coordinates analysis, coupled with a canonical correspondence analysis, showed spatial variations in the bacterial community composition. The water physical properties (e.g., Cr⁶⁺, total phosphorus, and COD_Mn); altitude; and land use (e.g., urban land cover and aquaculture) determined the distribution of the bacterioplankton composition. PICRUSt2 revealed that the overall functional profiles of the bacterial communities in different samples were similar, and our results suggested the potential health risks of water sources in this area. This work provided valuable insight into the composition of the plankton bacterial community and its relationship with the environmental factors in the Huangshui River in the ecotone zone of the Qinghai Plateau and Loess Plateau and a theoretical foundation for ecological health management.

Insight into Bacterial Community Responses to Polycyclic Aromatic Hydrocarbons and the Degradation Potentials of Three Bacterial Isolates in Seagrass Halophila ovalis Sediments

Seagrass meadows constitute a prestigious ecosystem in the marine environment, providing valuable ecological and commercial services. Among the various causes, pollutions are considered one of the significant reasons for seagrass decline globally. This study investigates the impacts of polycyclic aromatic hydrocarbons mixture (pyrene, phenanthrene, and fluorene) on bacterial communities in Halophila ovalis sediments. The seagrass sediment bacterial microbiome was evaluated in a batch culture experiment by Illumina MiSeq sequencing. Culture-able bacterial strains were isolated and characterized by 16S rRNA gene sequencing. The results demonstrated an excellent alpha diversity in the original sediments with a Shannon index of (8.078) compared to the subsequent control group (5.908) and PAH-treated group (PAH-T) (4.916). Three phyla, Proteobacteria, Firmicutes, and Bacteroidetes, were detected in high abundance in the control and PAH-T groups. However, a significant difference (P < 0.05) was observed at the genus level between control and PAH-T group bacterial consortia. Pseudomonas, Mycobacterium, Idiomarina, Hydrogenophaga, Alteromonas, Sphingobacterium, and several others were highly abundant in PAH-T groups. Most of the culture-able isolates recovered in this study showed the closest resemblance to previously identified hydrocarbon-degrading bacteria. Among the three strains, Mix-16 (Citricoccus yambaruensis) and Mix-20 (Gordonia rubripertincta) showed a higher degradation of PAHs than Mix-19 (Isoptericola halotolerans) in the monoculture experiment. The most increased degradation of PAHs was recorded in the co-culture experiment. The present work revealed that PAHs could act as environmental stress and can influence bacterial community succession. Moreover, the co-culture strategy significantly enhanced the biodegradation of PAHs.

Effect of pyrene and phenanthrene in shaping bacterial communities in seagrass meadows sediments

Polycyclic aromatic hydrocarbons (PAHs), originating from anthropogenic and natural sources, are highly concerned environmental pollutants. This study investigated the impact of two model PAHs (pyrene and phenanthrene) on bacterial community succession in the seagrass meadows sediment in a lab-scale microcosm. Halophila ovalis sediment slurry microcosms were established, one group was placed as a control, and the other two were treated with pyrene and phenanthrene. Bacterial community succession in response to respective PAHs was investigated by 16S rRNA amplicon sequencing. The results demonstrated that bacterial diversity decrease in each microcosm during the incubation process; however, the composition of bacterial communities in each microcosm was significantly different. Proteobacteria (37-89%), Firmicutes (9-41%), and Bacteroides (7-21%) were the predominant group at the phylum levels. Their abundance varies during the incubation process. Several previously reported hydrocarbon-degrading genera, such as Pseudomonas, Spinghobium, Sphingobacterium, Mycobacterium, Pseudoxanthomonas, Idiomarina, Stenotrophomonas, were detected in higher abundance in pyrene- and phenanthrene-treated microcosms. However, these genera were distinctly distributed in the pyrene and phenanthrene treatments, suggesting that certain bacterial groups favorably degrade different PAHs. Statistical analyses, such as ANOSIM and PERMANOVA, also revealed that significant differences existed among the treatments' bacterial consortia (P < 0.05). This work showed that polycyclic aromatic hydrocarbon significantly affects bacterial community succession, and different PAHs might influence the bacterial community succession differently.

Bacterial Taxa Migrating from the Mediterranean Sea into the Red Sea Revealed a Higher Prevalence of Anti-Lessepsian Migrations

In 1869, the Suez Canal was opened, which brought the waters of the Mediterranean and the Red Sea into direct contact. Notably, the Suez Canal was constructed for navigation purposes without focusing on the ecological impacts. The Suez Canal paved the way for species migration from the Red Sea to the Mediterranean Sea through Lessepsian migration, named after Ferdinand de Lesseps, while the migration from the Mediterranean Sea to the Red Sea is called the anti-Lessepsian migration. It has been argued in the past that the migrating species had negative consequences for the host environment as well as of humans. Few studies to date have attempted to map the microorganism migration problem because the traditional ways of measuring the community's richness and dissimilarities failed to provide enough detection of the migrating taxa. We collected 22 seawater samples from different locations in Egypt, in relationship to the migration across and to/from the Suez Canal. The V3-V4 regions of 16s genes were amplified and sequenced by the next generation Illumina MiSeq sequencer. Bioinformatics analysis revealed 15 taxa that migrated from the Mediterranean Sea to the Red Sea (i.e., anti-Lessepsian migration) such as the genera Fluvicola, HTCC2207, and Persicirhabdus. The family OCS155 is the only one that migrated from the Red Sea to the Mediterranean Sea (Lessepsian migration). Seven anti-Lessepsian migrants colonized the Suez Canal more than the Mediterranean Sea such as the genera Marinobacter and Halomonas. These findings collectively suggest that the anti-Lessepsian migration is more predominant than the Lessepsian migration in the bacterial community. This study paves the way for future research questions as well. For example, why is the anti-Lessepsian migration more common than the Lessepsian route in bacteria? Why do certain taxa stop migration at the Suez Canal, and why do certain taxa present in higher frequencies in the Suez Canal? Which taxa continue migration to the Indian Ocean and the Atlantic Ocean, and what is the impact of the anti-Lessepsian migration on the bacterial community? Understanding microbial diversity in a context of microorganism migration across seas and oceans remains a prime topic in biodiversity research and systems science.

The distinct response of phenanthrene enriched bacterial consortia to different PAHs and their degradation potential: a mangrove sediment microcosm study

Understanding the microbial community succession to polycyclic aromatic hydrocarbons (PAHs) and identification of important degrading microbial groups are crucial for the designing of appropriate bioremediation strategies. In the present study, two distinct phenanthrene enriched bacterial consortia were treated against high molecular weight (Pyrene, Benzo (a) pyrene and Benzo (a) fluoranthene) and the response was studied in term of taxonomic variations by using High Throughput Illumina sequencing and qPCR analysis. Overall, the type of PAHs significantly affected the composition and the relative abundance of bacterial communities while no obvious difference was detected between bacterial communities of benzo (a) pyrene and benzo (a) fluoranthene treatments. Genera, Novosphingobium, Pseudomonas, Flavobacterium, Mycobacterium, Hoeflae, and Algoriphagus dominated all PAHs treatment groups indicating that they could be the key PAHs degrading phylotypes. Due to the higher abundance of gram-negative PAH-ring hydroxylating dioxygenase gene than that of gram-positive bacteria in all treated groups, we speculated that gram-negative bacteria may contribute more in the PAH degradation. The studied sediments harbored rich PAHs degrading bacterial assemblages involved in both low and high molecular weight PAHs and these findings provided new insight into the perspective of microbial PAHs bioremediation in the mangrove ecosystem.

New insights into the responses of soil microorganisms to polycyclic aromatic hydrocarbon stress by combining enzyme activity and sequencing analysis with metabolomics

Polycyclic aromatic hydrocarbons (PAHs), some of the most widespread organic contaminants, are highly toxic to soil microorganisms. Whether long-term polluted soils can still respond to the fresh input of pollutants is unknown. In this study, the soil enzyme activity, soil microbial community structure and function and microbial metabolism pathways were examined to systematically investigate the responses of soil microorganisms to fresh PAH stress. Microbial activity as determined by soil dehydrogenase and urease activity was inhibited upon microbe exposure to PAH stress. In addition, the soil microbial community and function were obviously shifted under PAH stress. Both microbial diversity and richness were decreased by PAH stress. Rhizobacter, Sphingobium, Mycobacterium, Massilia, Bacillus and Pseudarthrobacter were significantly affected by PAH stress and can be considered important indicators of PAH contamination in agricultural soils. Moreover, the majority of microbial metabolic function predicted to respond to PAH stress were affected adversely. Finally, soil metabolomics further revealed specific inhibition of soil metabolism pathways associated with fatty acids, carbohydrates and amino acids. Therefore, the soil metabolic composition distinctively changed, reflecting a change in the soil metabolism. In summary, fresh contaminant introduction into long-term polluted soils inhibited microbial activity and metabolism, which might profoundly affect the whole soil quality.

Structural and functional shifts of bacterioplanktonic communities associated with spatiotemporal gradients in river outlets of the subtropical Pearl River Estuary, South China

In this study, we used high-throughput sequencing of 16S rRNA gene amplicons, to investigate the spatio-temporal variation in bacterial communities in surface-waters collected from eight major outlets of the Pearl River Estuary, South China. Betaproteobacteria were the most abundant class among the communities, followed by Gammaproteobacteria, Alphaproteobacteria, Actinobacteria, and Acidimicrobiia. Generally, alpha-diversity increased in winter communities and the taxonomic diversity of bacterial communities differed with seasonal and spatial differences. Temperature, conductivity, salinity, pH and nutrients were the crucial environmental factors associated with shifts in the bacterial community composition. Furthermore, inferred community functions that were associated with amino acid, carbohydrate and energy metabolisms were lower in winter, whereas the relative abundance of inferred functions associated with membrane transport, bacterial motility proteins, and xenobiotics biodegradation and metabolism, were enriched in winter. These results provide new insights into the dynamics of bacterial communities within estuarine ecosystems.