rRNA Gene Amplicon Sequencing Analysis Research Articles

Phagotrophy in the nitrogen-fixing haptophyte Braarudosphaera bigelowii.

Biological nitrogen fixation provides fixed nitrogen for microbes living in the oligotrophic open ocean. UCYN-A2, the previously known symbiont of Braarudosphaera bigelowii, now believed to be an early-stage B. bigelowii organelle that exchanges fixed nitrogen for fixed carbon, is globally distributed. Indirect evidence suggested that B. bigelowii might be a mixotrophic (phagotrophic) phototrophic flagellate. The goal of this study was to determine if B. bigelowii can graze on bacteria using several independent approaches. The results showed that B. bigelowii grazed on co-occurring bacteria at a rate of 5-7 cells/h/B. bigelowii and that the overall grazing rate was significantly higher at nighttime than at daytime. Bacterial abundance changes, assessed with 16S rRNA gene amplicon sequencing analysis, may have indicated preferential grazing by B. bigelowii on specific bacterial genotypes. In addition, Lysotracker™ staining of B. bigelowii suggested digestive activity inside B. bigelowii. Carbon and nitrogen fixation measurements revealed that the carbon demand of B. bigelowii could not be fulfilled by photosynthesis alone, implying supplementation by heterotrophy. These independent lines of evidence together revealed that B. bigelowii engages in phagotrophy, which, beyond serving as a supplementary source of carbon and energy, may also facilitate the indirect assimilation of inorganic nutrients.

Relationships between the gut microbiome and brain functional alterations in first-episode, drug-naïve patients with major depressive disorder

ObjectiveIncreasing evidence has shown that the microbiota-gut-brain axis (MGB) is involved in the mechanism of major depressive disorder (MDD). However, the relationship between the gut microbiome and brain function in MDD patients has not been determined. Here, we intend to identify specific changes in the gut microbiome and brain function in first-episode, drug-naïve MDD patients and then explore the associations between the two omics to elucidate how the MGB axis plays a role in MDD development. MethodsWe recruited 38 first-episode, drug-naïve MDD patients and 37 healthy controls (HC). The composition of the fecal microbiome and neural spontaneous activity alterations were examined using 16S rRNA gene amplicon sequencing analysis and regional homogeneity (ReHo). Spearman correlation analyses were conducted to assess the associations between the gut microbiome and brain function. ResultsCompared with HC, MDD patients exhibited distinct alterations in the gut microbiota and elevated ReHo in the frontal regions. In the MDD group, a positive relationship was noted between the relative abundance of Blautia and the HAMD-17 and HAMA scores, as well as between the relative abundance of Oxalobacteraceae and the HAMD-17 score. The relative abundances of Porphyromonadaceae and Parabacteroides were negatively correlated with the ReHo values of frontal regions. LimitationsOur study utilized a cross-sectional design, and the number of subjects was relatively small. ConclusionWe found that some specific gut microbiomes were associated with frontal function, and others were associated with clinical symptoms in MDD patients, which may support the role of the MGB axis underlying MDD.

Buccal Swab Samples from Japanese Brown Cattle Fed with Limonite Reveal Altered Rumen Microbiome.

The areas of the Mount Aso grasslands in Kumamoto, Japan, are the primary location for the breeding of the Kumamoto strain of Japanese Brown cattle (JBRK). Although Aso limonite, deposited by volcanic ash and magma, has been commonly fed to pregnant JBRK in this area, the mechanisms of its salutary effects on pregnant JBRK have not yet been elucidated. Approximately 100 days before the expected day of calf delivery, seven JBRK (four supplemented with limonite and three controls without limonite) were assigned to this study, from which a buccal swab was collected at the highest rumination every 30 days for 90 days. DNA extracted from these swabs was then analyzed using a 16S rRNA gene amplicon sequence analysis. Statistically significant differences between the two groups were discovered through beta-diversity analysis, though results from alpha-diversity analysis were inconclusive. The microbiota identified were classified into six clusters, and three of the main clusters were core-rumen bacteria, primarily cellulose digestion in cluster 1, oral bacteria in cluster 2, and non-core-rumen bacteria in cluster 3. In the limonite group, core-rumen bacteria decreased while non-core-rumen bacteria increased, suggesting that limonite feeding alters rumen microbiota, particularly activation of non-core-rumen microbiota.

Distribution of bacterial community structures and spread of antibiotic resistome at industrially polluted sites of Mini River, Vadodara, Gujarat, India.

The influence of anthropogenic pollution on the distribution of bacterial diversity, antibiotic-resistant bacteria (ARBs), and antibiotic resistance genes (ARGs) was mapped at various geo-tagged sites of Mini River, Vadodara, Gujarat, India. The high-throughput 16S rRNA gene amplicon sequencing analysis revealed a higher relative abundance of Planctomycetota at the polluted sites, compared to the pristine site. Moreover, the relative abundance of Actinobacteriota increased, whereas Chloroflexi decreased in the water samples of polluted sites than the pristine site. The annotation of functional genes in the metagenome samples of Mini River sites indicated the presence of genes involved in the defence mechanisms against bacitracin, aminoglycosides, cephalosporins, chloramphenicol, streptogramin, streptomycin, methicillin, and colicin. The analysis of antibiotic resistome at the polluted sites of Mini River revealed the abundance of sulfonamide, beta-lactam, and aminoglycoside resistance. The presence of pathogens and ARB was significantly higher in water and sediment samples of polluted sites compared to the pristine site. The highest resistance of bacterial populations in the Mini River was recorded against sulfonamide (≥ 7.943 × 103CFU/mL) and ampicillin (≥ 8.128 × 103CFU/mL). The real-time PCR-based quantification of ARGs revealed the highest abundance of sulfonamide resistance genes sul1 and sul2 at the polluted sites of the Mini River. Additionally, the antimicrobial resistance genes aac(6')-Ib-Cr and blaTEM were also found abundantly at polluted sites of the Mini River. The findings provide insights into how anthropogenic pollution drives the ARG and ARB distribution in the riverine ecosystem, which may help with the development of antimicrobial resistance mitigation strategies.

Effects of squamous cell carcinoma and smoking status on oropharyngeal and laryngeal microbial communities.

Still, little is known about microbial dysbiosis in oropharyngeal and laryngeal tissue as risk factor for development of local squamous cell carcinoma. The site-specific microbiota at these regions in healthy and cancer tissue and their modulation by environmental factors need to be defined. The local microbiota of cancer tissue and healthy controls was profiled by 16S rRNA gene amplicon sequencing and statistical analysis using 111 oropharyngeal and 72 laryngeal intraoperative swabs. Oropharynx and larynx harbor distinct microbial communities. Clear effects of both smoking and cancer were seen in the oropharynx whereas effects in the larynx were minor. The distinct microbial communities at larynx and oropharynx partially explain why the effects of cancer and smoking were distinct at those sites. Thus, the use of microbiota supposed to mirror community changes in another target location should be avoided and more studies on the actual cancerous environment are necessary.

Green tuff supplementation improves plant growth and microbial interactions of soil aggregates and rhizosphere in cherry tomato (Solanum lycopersicum L. var. cerasiforme) cultivation

Soil and rhizosphere microorganisms play essential roles in nutrient cycling and plant growth promotion in agricultural systems. Natural mineral materials, such as zeolite, are widely used as soil amendment materials to create “healthy” conditions for microorganisms related to plant cultivation. However, the effects of these minerals on microbial community structures in the soil with different aggregate scales and rhizosphere are largely unknown. In this study, we used cherry tomato (Solanum lycopersicum L. var. cerasiforme) cultivation experiment fed with 80 kg/1000 m2 green tuff (GT) as a natural soil amendment material and without GT (control blank as conventional farming; CK). The total yield and average root weight in GT were 1.2-fold and 1.6-fold higher than those in CK, respectively. The 16S rRNA gene amplicon sequence analysis in size-fractionated soil samples showed that the genus Bacillus, known as plant growth-promoting bacteria (PGPB), was significantly increased in bulk soil (nonfractionated soil), large macroaggregates (LMA, 5.6 mm–1 mm diameter), and small macroaggregates (SMA, 1 mm–250 μm diameter) in GT, and the genus Nocardioides, known as PGPB, was significantly increased in the rhizosphere of GT compared with CK (p < 0.05). These microorganisms had significant positive correlations with several PGPB, such as Bacillus, Nocardioidaceae, and Mesorhizobium. These results suggest that green tuff supplementation improves the microbial interactions in the soils, yields and root weight of cherry tomato.

Quantitative detection and reduction of potentially pathogenic bacterial groups of Aeromonas, Arcobacter, Klebsiella pneumoniae species complex, and Mycobacterium in wastewater treatment facilities.

Water quality parameters influence the abundance of pathogenic bacteria. The genera Aeromonas, Arcobacter, Klebsiella, and Mycobacterium are among the representative pathogenic bacteria identified in wastewater. However, information on the correlations between water quality and the abundance of these bacteria, as well as their reduction rate in existing wastewater treatment facilities (WTFs), is lacking. Hence, this study aimed to determine the abundance and reduction rates of these bacterial groups in WTFs. Sixty-eight samples (34 influent and 34 non-disinfected, treated, effluent samples) were collected from nine WTFs in Japan and Thailand. 16S rRNA gene amplicon sequencing analysis revealed the presence of Aeromonas, Arcobacter, and Mycobacterium in all influent wastewater and treated effluent samples. Quantitative real-time polymerase chain reaction (qPCR) was used to quantify the abundance of Aeromonas, Arcobacter, Klebsiella pneumoniae species complex (KpSC), and Mycobacterium. The geometric mean abundances of Aeromonas, Arcobacter, KpSC, and Mycobacterium in the influent wastewater were 1.2 × 104-2.4 × 105, 1.0 × 105-4.5 × 106, 3.6 × 102-4.3 × 104, and 6.9 × 103-5.5 × 104 cells mL-1, respectively, and their average log reduction values were 0.77-2.57, 1.00-3.06, 1.35-3.11, and -0.67-1.57, respectively. Spearman's rank correlation coefficients indicated significant positive or negative correlations between the abundances of the potentially pathogenic bacterial groups and Escherichia coli as well as water quality parameters, namely, chemical/biochemical oxygen demand, total nitrogen, nitrate-nitrogen, nitrite-nitrogen, ammonium-nitrogen, suspended solids, volatile suspended solids, and oxidation-reduction potential. This study provides valuable information on the development and appropriate management of WTFs to produce safe, hygienic water.

Residual chlorine persistently changes antibiotic resistance gene composition and increases the risk of antibiotic resistance in sewer systems

During the COVID-19 pandemic, excessive amounts of disinfectants and their transformation products entered sewer systems worldwide, which was an extremely rare occurrence before. The stress of residual chlorine and disinfection by-products is not only likely to promote the spread of antibiotic resistance genes (ARGs), but also leads to the enrichment of chlorine-resistant bacteria that may also be resistant to antibiotics. Therefore, the potential impact of such discharge on ARG composition should be studied and the health risks should be assessed. Thus, this study combined high-throughput 16S rRNA gene amplicon sequencing and metagenomic analysis with long-term batch tests that involved two stages of stress and recovery to comprehensively evaluate the impact of residual chlorine on the microbial community and ARG compositions in sewer systems. The tests demonstrated that the disturbance of the microbial community structure by residual chlorine was reversible, but the change in ARG composition was persistent. This study found that vertical propagation and horizontal gene transfer jointly drove ARG composition succession in the biofilm, while the driving force was mainly horizontal gene transfer in the sediment. In this process, the biocide resistance gene (BRG) subtype chtR played an important role in promoting co-selection with ARGs through plasmids and integrative and conjugative elements. Moreover, it was further shown that the addition of sodium hypochlorite increased the risk of ARGs to human health, even after discontinuation of dosing, signifying that the impact was persistent. In general, this study strengthens the co-selection theory of ARGs and BRGs, and calls for improved disinfection strategies and more environmentally friendly disinfectants.

Archaea are better adapted to antimony stress than their bacterial counterparts in Xikuangshan groundwater

Archaea are important ecological components of microbial communities in various environments, but are currently poorly investigated in antimony (Sb) contaminated groundwater particularly on their ecological differences in comparison with bacteria. To address this issue, groundwater samples were collected from Xikuangshan aquifer along an Sb gradient and subjected to 16S rRNA gene amplicon sequencing and bioinformatic analysis. The results demonstrated that bacterial communities were more susceptibly affected by elevated Sb concentration than their archaeal counterparts, and the positive stimulation of Sb concentration on bacterial diversity coincided with the intermediate disturbance hypothesis. Overall, the balance of environmental variables (Sb, pH, and EC), competitive interactions, and stochastic events jointly regulated bacterial and archaeal communities. Linear fitting analysis revealed that Sb significantly drove the deterministic process (heterogeneous selection) of bacterial communities, whereas stochastic process (dispersal limitation) contributed more to archaeal community assembly. In contract, the assembly of Sb-resistant bacteria and archaea was dominated by the stochastic process (undominated), which implied the important role of diversification and drift instead of selection. Compared with Sb-resistant microorganisms, bacterial and archaeal communities showed lower niche width, which may result from the constraints of Sb concentration and competitive interaction. Moreover, Sb-resistant archaea had a higher niche than that of Sb-resistant bacteria via investing on flexible metabolic pathways such as organic metabolism, ammonia oxidation; and carbon fixation to enhance their competitiveness. Our results offered new insights into the ecological adaptation mechanisms of bacteria and archaea in Sb-contaminated groundwater.

Microbial communities associated with landfarming amendments during bioremediation of crude oil in Niger Delta soils

Landfarming is a widely utilized process that involves using bacterial biodegradation to remediate contaminated soil resulting from oil spillages. Its effectiveness can be improved using amendments that include fertilizers, biosurfactants, enzymes, and natural sorbents. The effects of these amendments on biodegradation efficiency and the microbial community composition were investigated using 16S rRNA gene amplicon sequencing analyses performed on soil samples collected from a large-scale mesocosm experiment. The results showed that the use of amendments had a profound influence on the microbial community, which decreased with time following application of the amendment. Interestingly, the relationship between observed microbial diversity and biodegradation efficiency changed over time. During the initial phase, a higher biodegradation rate correlated with lower biodiversity indices, while during the later phase this relation reversed, and a higher biodegradation rate correlated with higher biodiversity indices. Two mesocosms types, one with biochar plus rhamnolipids and the other with agricultural lime, both in combination with fertilizer, degraded the oil significantly better than the ‘oil-only control’ with biodegradation improvements of 32.5 % and 25.8 %, respectively. Both combinations of amendments also promoted different adaptive responses of the microbial community with higher abundances of members of the genus Sphingomonas in both cases.

Bacterial Community Composition Under Paddy Conditions Is More Strongly Affected by the Difference in Soil Type than by Field Management.

In this study, we aimed to investigate the effects of soil type and field management on bacterial communities in paddy soils, taking into account the differences in soil physicochemical properties. We collected soil samples from 51 paddy fields in six prefectures in Japan. The paddy fields were managed under organic regimes (26 fields), natural-farming regimes (12 fields), or conventional regimes (13 fields). The paddy fields were classified into four soil types: andosol, gray lowland soil, gley soil, and gray upland soil. Soil DNA was extracted from the soil samples collected 2 to 10 weeks after the flooding, and the 16S rRNA gene amplicon sequencing analysis was performed. The bacterial community compositions were dominated by the phylum Proteobacteria, Chloroflexi, Actinobacteria, Acidobacteria, and Firmicutes in all fields. The difference in soil type had significant effects on α-diversities of the bacterial communities, although the field management had no effect. The soil bacterial communities in the gley soils and gray upland soils individually formed different groups from those in the other soils, while the andosol and gray lowland soils tended to form relatively similar bacterial communities. On the other hand, the effects of the field management were estimated to be smaller than those of soil type. The β-diversity of the bacterial community compositions were significantly correlated with soil pH, total nitrogen content, total carbon content, and divalent iron content. Our results suggest that the soil microbial community in paddy fields may be strongly influenced by soil physiochemical properties derived from differences in soil type.

Validation of a batch cultivation protocol for fecal microbiota of Kenyan infants

BackgroundThe combination of cultivation studies with molecular analysis approaches allows characterization of the complex human gut microbiota in depth. In vitro cultivation studies of infants living in rural sub-Saharan Africa are scarce. In this study, a batch cultivation protocol for Kenyan infant fecal microbiota was validated.MethodsFresh fecal samples were collected from 10 infants living in a rural area of Kenya. Samples were transported under protective conditions and subsequently prepared for inoculation within less than 30 h for batch cultivation. A diet-adapted cultivation medium was used that mimicked the daily intake of human milk and maize porridge in Kenyan infants during weaning. 16 S rRNA gene amplicon sequencing and HPLC analyses were performed to assess the composition and metabolic activity, respectively, of the fecal microbiota after 24 h of batch cultivation.ResultsHigh abundance of Bifidobacterium (53.4 ± 11.1%) and high proportions of acetate (56 ± 11% of total metabolites) and lactate (24 ± 22% of total metabolites) were detected in the Kenyan infant fecal microbiota. After cultivation started at an initial pH 7.6, the fraction of top bacterial genera (≥ 1% abundant) shared between fermentation and fecal samples was high at 97 ± 5%. However, Escherichia-Shigella, Clostridium sensu stricto 1, Bacteroides and Enterococcus were enriched concomitant with decreased Bifidobacterium abundance. Decreasing the initial pH to 6.9 lead to higher abundance of Bifidobacterium after incubation and increased the compositional similarity of fermentation and fecal samples. Despite similar total metabolite production of all fecal microbiota after cultivation, inter-individual differences in metabolite profiles were apparent.ConclusionsProtected transport and batch cultivation in host and diet adapted conditions allowed regrowth of the top abundant genera and reproduction of the metabolic activity of fresh Kenyan infant fecal microbiota. The validated batch cultivation protocol can be used to study the composition and functional potential of Kenyan infant fecal microbiota in vitro.

Microbial dynamics in shallow CO2 seeps system off Panarea Island (Italy)

Shallow-water hydrothermal vents are extreme environments characterized by high temperatures, low pH, and high CO2 concentrations; therefore, they are considered as suitable laboratories for studying the effect of global changes on marine microbes. We hypothesized a direct effect of vents on prokaryotic community structure and functioning in the Panarea Island’s hydrothermal system. Sampling was conducted along a 9-station transect characterized by three active emission points. The water column was stratified with a thermocline at 25 m depth and a deep chlorophyll maximum between 50 and 100 m. Prokaryotic abundance ranged from 0.2 to 1.5 × 109 cells L−1, prokaryotic carbon production from 2.4 to 75.4 ng C L−1 h−1, and exoenzymatic activities degrading proteins, phosphorylated compounds, and polysaccharides were on the order of 4–28, 2–31 and 0.2–4.16 nM h−1, respectively. While microbial abundance and production were shaped by the water column's physical structure, alkaline phosphatase and beta-glucosidase activities seemed to be enhanced by hydrothermal fluids. The 16S rRNA gene amplicon sequencing analysis identified a surface, a deep, and a vent-influenced microbial community. In terms of relative abundance members of the SAR11 group dominated the water column, alongside Synechococcus and Prochlorococcus in surface and bottom samples, respectively. Vent-influenced stations were characterized by the presence of Thiomicrorhabdus, a sulfur-oxidizer chemolithoautotroph. Overall, this study provides insights on the coupling between microbial community structure and the biogeochemical cycling of nutrients in low-pH conditions (CO2 and H2S-based), thus addressing some of the opened questions about the response of microbes to acidification.

Microgravity stress alters bacterial community assembly and co-occurrence networks during wheat seed germination

Bacterial interactions occurring on and around seeds are integral to plant fitness, health and productivity. Although seed- and plant-associated bacteria are sensitive to environmental stress, the effects of microgravity, as present during plant cultivation in space, on microbial assembly during seed germination are not clear. Here, we characterized the bacterial microbiome assembly process and mechanisms during seed germination of two wheat varieties under simulated microgravity by 16S rRNA gene amplicon sequencing and metabolome analysis. We found that the bacterial community diversity, and network complexity and stability were significantly decreased under simulated microgravity. In addition, the effects of simulated microgravity on the plant bacteriome of the two wheat varieties tended to be consistent in seedlings. At this stage, the relative abundance of Oxalobacteraceae, Paenibacillaceae, Xanthomonadaceae, Lachnospiraceae, Sphingomonadaceae and Ruminococcaceae decreased, while the relative abundance of Enterobacteriales increased under simulated microgravity. Analysis of predicted microbial function revealed that simulated microgravity exposure leads to lower sphingolipid signaling and calcium signaling pathways. We also found that simulated microgravity drove the strengthening of deterministic processes in microbial community assembly. Importantly, some specific metabolites exhibited significant changes under simulated microgravity, suggesting that bacteriome assembly is mediated, at least in part, by metabolites altered by microgravity. The data we present here moves us closer to a holistic understanding of the plant bacteriome under microgravity stress at plant emergence, and provides a theoretical basis for the precise utilization of microorganisms in microgravity to improve plant adaptation to the challenge of cultivation in space.

Composition and transcriptional activity of oil reservoir microorganisms under different gas/liquid ratios

Microorganisms inhabited in oil reservoirs play a fundamental role in microbial enhanced oil recovery. Gas injection has been adopted as an alternative method in the tertiary oil recovery, but the influence of the gas injection on microbial composition in oil reservoir and its contribution to oil recovery still remained unclear. In this study, the effect of air injection on the microbial composition and transcriptional activity is investigated using a combination of the 16S rRNA gene amplicon sequencing, metagenomic and meta-transcriptomic analysis. Firmicutes were the main active bacteria in all samples and the proportion of Firmicutes increased with the rising of gas/liquid ratio in samples without additional treatment. The Bacillus was the dominant member of phylum Firmicutes. With the increase of gas-to-liquid ratios, the microbes showed higher overall transcription activities and propionate become an important metabolite. This research provides theoretical guidance for the activation of endogenous oil displacement microorganisms and sheds light on the industrial applications for exploitation of depleted reservoirs and the extension of the development life of oil reservoirs.

P094 Impacts of 5-aminosalicylic acid on the intestinal microbiota leading to the anti-inflammatory effect

Abstract Background 5-aminosalicylic acid (5-ASA) is widely used for the treatment of inflammatory bowel disease (IBD), while its anti-inflammatory mechanisms remain controversial. The intestinal microbiota plays a certain role in the pathogenesis of IBD. We hypothesised that 5-ASA exerts anti-inflammatory effects by altering the gut microbiota. Elucidating the effects of 5-ASA on gut microbiota and its contribution to anti-inflammatory effects can lead to the development of effective and economical IBD medications. Methods Specific-pathogen-free (SPF) mice were orally administered 5-ASA for 4 weeks. The fecal bacterial compositions were examined with 16S rRNA gene amplicon sequencing analysis in mice of the 5-ASA-treatment group (5-ASA group) and no-treatment group (NT group). The immune profiles of the colonic mucosa were assessed. The feces from female mice in both groups were gavaged into germ-free (GF) female mice in separated isolators. In each isolator, these female mice (5-ASA dams and NT dams) were mated with GF male mice. The populations of CD4+ T cells in mesenteric lymph nodes (MLN) and colonic mucosal immune profiles were analysed in their pups. The pups were used for the dextran sulfate sodium (DSS)-induced colitis model to evaluate the anti-inflammatory effects of the gut microbiota altered by 5-ASA. Results The fecal bacterial compositions changed with 5-ASA treatment over time in SPF mice. At the genus level, the relative abundance of Allobaculum increased significantly in the females of the 5-ASA group compared to the NT group (corrected p &amp;lt; 0.05). The same tendency was observed in male counterparts. The mRNA expression of IL-10 and IL-22 in the colonic mucosa increased significantly in mice of the 5-ASA group compared to their counterparts (p &amp;lt; 0.05 in both sexes). In each isolator, the fecal bacterial compositions were similar between the dams and pups, suggesting that the gut microbiota was vertically transmitted from the dams to the pups in each group. CD4+RORgt+ T cells increased in MLN in the pups of 5-ASA dams compared to those of NT dams (p &amp;lt; 0.01). The mRNA expression of TGF-b, claudin-2 and claudin-3 in the colonic mucosa increased significantly (p &amp;lt; 0.001). The colonic inflammation induced by DSS was milder in 5-ASA pups compared to NT pups (Figure 1). Conclusion Orally-administered 5-ASA altered the intestinal microbiota affecting the host immune system and leading to less susceptibility to DSS-induced colitis. Alteration of gut microbiota could be a part of the anti-inflammatory mechanisms of 5-ASA.

Impacts of dibutyl phthalate on bacterial community composition and carbon and nitrogen metabolic pathways in a municipal wastewater treatment system

Dibutyl phthalate (DBP) is a typical toxic and hazardous pollutant in pharmaceutical wastewater, affecting the metabolism of microbial flora, leading to decreased treatment efficiency, and deteriorated effluent quality in municipal wastewater treatment plants (WWTPs). This study conducted a long-term experiment with 6 operational stages in a pilot-scale A2O-MBR system, analyzing the effect of DBP on the bacterial community and their carbon and nitrogen metabolic pathways. 16S rRNA gene amplicon sequencing analysis and principal components analysis (PCA) showed that DBP at 8 mg/L significantly influenced the structure of bacterial community (P < 0.05), resulting in reduced bacterial community diversity. Metagenomic analysis was used to explore the embedded carbon and nitrogen metabolic pathways. At the presence of DBP, the metabolism of saccharides, lipids, and aromatic compounds were blocked owing to the vanishment of key enzyme (such as acetylaminohexosyltransferase (EC 2.4.1.92) and UDP-sugar pyro phosphorylase (EC 2.7.7.64)) encoding genes, resulting in weakened carbon metabolism, and thus reduced COD removal performance. The resultant deficiency of the genes such as those encoding hydroxyproline dehydrogenase (EC 1.5.5.3) gave rise to interrupted metabolic pathways of amino acid (arginine, proline, tyrosine, and tryptophan), resulting in declined function of nitrogen metabolism and thus reduced TN removal efficiency. The uncovery of the mechanisms by which DBP affects wastewater treatment system efficiency and microbial metabolism is of theoretical importance for the efficient operation of municipal and pharmaceutical wastewater treatment systems.

Microbial dynamics and bioreactor performance are interlinked with organic matter removal from wastewater treatment plant effluent

Optimizing bioreactor performance for organic matter removal can achieve sustainable and energy-efficient micropollutant removal in subsequent tertiary treatment. Bioreactor performance heavily depends on its resident microbial community; hence, a deeper understanding of community dynamics is essential. The microbial communities of three different bioreactors (biological activated carbon, moving bed biofilm reactor, sand filter), used for organic matter removal from wastewater treatment effluent, were characterized by 16S rRNA gene amplicon sequence analysis. An interdependency between bioreactor performance and microbial community profile was observed. Overall, Proteobacteria was the most predominant phylum, and Comamonadaceae was the most predominant family in all bioreactors. The relative abundance of the genus Roseococcus was positively correlated with organic matter removal. A generalized Lotka-Volterra (gLV) model was established to understand the interactions in the microbial community. By identifying microbial dynamics and their role in bioreactors, a strategy can be developed to improve bioreactor performance.

Bacterial Profiles of Brain in Downer Cattle with Unknown Etiology.

Downer cow can be caused by muscular paralysis, neurological damage, metabolic disorder, and/or the complication of microbial infection. However, downer cow with unknown etiology is issued because of the non-detection of its bacterial etiological agent. In this study, differences in the bacterial community in brain tissues between downer cattle with unknown etiology and healthy slaughtered cattle are investigated. Bacterial diversity and representative genera between downer and normal cattle were significantly different (p < 0.05). There are significant differences in representative genera of downer and normal cattle, especially the significance, fold change, and area under the receiver operating characteristic curve score (p < 0.05). Furthermore, the prediction of functional genes in brain microbiota between the downer and normal cattle revealed differences in the cluster of orthologous gene categories, such as lipid transport and metabolism, secondary metabolite biosynthesis, and signal transduction (p < 0.05). This study revealed a significant difference in microbiota between the downer and normal cattle. Thus, we demonstrate that representative genera from downer cattle through 16S rRNA gene amplicon sequencing and microbiota analysis have the potential as candidates for bacterial etiological agents for downer cow.

Non-caloric artificial sweeteners modulate conjugative transfer of multi-drug resistance plasmid in the gut microbiota

ABSTRACT Non-caloric artificial sweeteners have been widely permitted as table sugar substitutes with high intensities of sweetness. They can pass through the intestinal tract without significant metabolization and frequently encounter the gut microbiome, which is composed of diverse bacterial species and is a pool of antibiotic resistance genes (ARGs). However, little is known about whether these sweeteners could accelerate the spread of ARGs in the gut microbiome. Here, we established an in vitro conjugation model by using Escherichia coli that carries chromosome-inserted Tn7 lacIq-pLpp-mCherry and plasmid-encoded gfpmut3b gene as the donor and murine fecal bacteria as the recipient. We found that four commonly used artificial sweeteners (saccharin, sucralose, aspartame, and acesulfame potassium) can increase reactive oxygen species (ROS) production and promote plasmid-mediated conjugative transfer to the gut microbiome. Cell sorting and 16S rRNA gene amplicon sequencing analysis of fecal samples reveal that the tested sweeteners can promote the broad-host-range plasmid permissiveness to both Gram-negative and Gram-positive gut bacteria. The increased plasmid permissiveness was also validated with a human pathogen Klebsiella pneumoniae. Collectively, our study demonstrates that non-caloric artificial sweeteners can induce oxidative stress and boost the plasmid-mediated conjugative transfer of ARGs among the gut microbiota and a human pathogen. Considering the soaring consumption of these sweeteners and the abundance of mobile ARGs in the human gut, our results highlight the necessity of performing a thorough risk assessment of antibiotic resistance associated with the usage of artificial sweeteners as food additives.