Bacterial Characteristics Research Articles

Dynamics of the glucosinolate–myrosinase system in tuber mustard (Brassica juncea var. tumida) during pickling and its relationship with bacterial communities and fermentation characteristics

Pickled tuber mustard is a traditional fermented pickle widely consumed in China, and it is characterized by the presence of glucosinolates (GSLs). To understand the biotransformation of GSLs in tuber mustard during pickling, the dynamics of the glucosinolate–myrosinase (GSL-MYR) system and its potential associations with bacterial communities and fermentation characteristics (i.e., salinity, titratable acidity [TAA], and pH) were investigated. In total, 18 GSLs were identified in fresh tuber mustard; 12 were aliphatic, 4 were indolic, and 2 were aromatic, with aliphatic sinigrin and aromatic gluconasturtiin being the dominating components. The pickling process resulted in complete degradation of GSLs, with isothiocyanates (ITCs) and nitriles being the main breakdown products. Total ITCs reached maximum concentrations on day 21–28, while total nitriles peaked at the end of pickling. Based on Spearman’s correlation analysis, our study showed that lactic acid bacteria (LAB) species might contribute to GSL transformation in pickled tuber mustard. Specifically, Weissella paramesenteroides, Pediococcus pentosaceus, and unclassified Lactococcus exhibited positive correlations with GSL contents (p < 0.01), suggesting that they might contribute to the increasing amounts of GSLs in the initial pickling, while the Lactobacillus-related populations that dominated in the later stages (i.e., Companilactobacillus alimentarius and Lactiplantibacillus Plantarum) were positively correlated with nitrile product concentrations. Moreover, redundancy analysis showed that pH and TAA had strong effect on myrosinase activity during tuber mustard pickling, which was dictated via the organic acids produced by microorganisms. This study provided a perspective for understanding the effect of fermentation on the transformation of tuber mustard GSLs.

Gut community alterations associated with Clostridioides difficile colonization in hospitalized gastroenterological patients with or without inflammatory bowel disease

Clostridioides difficile colonization and development of infection commonly occur in inflammatory bowel disease (IBD) patients and can trigger flare-ups. Both conditions are inherently linked to disrupted gut microbiota. This study included 149 hospitalized gastrointestinal patients, which were divided into IBD (n = 48) and non-IBD patients (n = 101). Patients were tested for C. difficile colonization (qPCR and selective plating), and gut bacterial communities were analyzed with 16S amplicon sequencing. Blood test results were retrospectively collected from the medical records. IBD and non-IBD patients had comparable C. difficile colonization rates (31.7 and 33.3%, respectively). Compared to non-IBD C. difficile-non-colonized patients, IBD and C. difficile-colonized patients shared multiple common bacterial community characteristics including decreased diversity and reduced abundance of strict anaerobic bacteria. Furthermore, certain microbiota alterations were enhanced when IBD was accompanied by C. difficile colonization, indicating a synergistic effect between both medical complications. Conversely, certain microbial patterns were specific to C. difficile colonization, e.g., co-occurrence with Enterococcus, which was most common in IBD patients (81.3%).

Effects of lead pollution on bacterial communities in biofilm attached to submerged plants.

Submerged plants and biofilms have significant advantages in hydro-ecology rehabilitation, but their tolerance and physiological responses to heavy metal stress have thus far been under-investigated. This study investigated the influence of lead on physiological and biochemical responses, as well as variation in bacterial communities and functional characteristics of submerged plant biofilms. The results showed that chlorophyll a content of two submerged plants decreased with increased lead concentration. The concentration of malondialdehyde of both submerged plants was higher under high lead concentrations than under low lead concentrations, and the concentrations of malondialdehyde and hydrogen peroxide in Vallisneria natans were more stable. The antioxidant enzyme systems of the two plants played protective roles against lead stress. High lead concentration can inhibit the bacterial community and lead to decreased diversity. The most abundant bacterial phyla were Proteobacteria (40.9%), Cyanobacteria (21.5%), and Bacteroidetes (14.3%). Proteobacteria abundance decreased with increased lead concentration, while Cyanobacteria abundance increased. The lead concentration in plants (19.7%, P < 0.01) and the lead concentration in aquatic environment (17.7%, P < 0.01) were significantly correlated with variation in bacterial communities. High lead concentration inhibits the activity of these bacteria related to the conversion of nitrogen and sulfur.

Depolymerized non-digestible sulfated algal polysaccharides produced by hydrothermal treatment with enhanced bacterial fermentation characteristics

Hydrothermal treatment was used to depolymerize sulfated polysaccharide extracted from Gracilaria chouae (GCP1) with an average molecular weight (Mw) of 1.79 × 10 3 kDa to produce three fractions GCP2, GCP3, and GCP4 with a Mw of 20.84, 8.25, and <5 kDa, respectively. While the chemical composition and monosaccharide profile of the three depolymerized GCPs were not significantly affected by the hydrothermal treatment. However, they exhibited lower apparent viscosity, storage modulus, and loss modulus. All four GCPs were shown to be nondigestible during simulated gastrointestinal digestion. During a 24-h in vitro fermentation using human fecal bacteria as inoculum, GCPs with lower Mw produced more short chain fatty acids (SCFAs), and lower branched chain fatty acids. Having the lowest Mw, GCP4 exhibited the best fermentation characteristics by inhibiting the growth of protein-fermentative bacteria including Bacteroides , Parabacteroides , Lachnoclostridium , and Phascolarctobacterium which have harmful effect and increased the relative abundance of butyrate-producing bacteria including Anaerostipes , Eubacterium , Roseburia , Ruminococcus and Lachnospira which are beneficial to gut health. The present study suggested that hydrothermal treatment could be used to prepare low Mw non-digestible polysaccharides that enhance the growth of beneficial bacteria for human gut health. • Polysaccharide from Gracilaria chouae was depolymerized using hydrothermal treatment. • Polysaccharides with lower Mw exhibited lower apparent viscosity, storage and loss modulus. • G. chouae polysaccharides with lower Mw showed better fermentation properties. • Hydrothermal treatment can be used to obtain polysaccharides with enhanced prebiotic activities.

Effects of different harvest frequencies on microbial community and metabolomic properties of annual ryegrass silage.

In this study, we analyzed the fermentation quality, microbial community, and metabolome characteristics of ryegrass silage from different harvests (first harvest-AK, second harvest-BK, and third harvest-CK) and analyzed the correlation between fermentative bacteria and metabolites. The bacterial community and metabolomic characteristics were analyzed by single-molecule real-time (SMRT) sequencing and ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS), respectively. After 60 days of ensiling, the pH of BK was significantly lower than those of AK and CK, and its lactic acid content was significantly higher than those of AK and CK. Lactiplantibacillus and Enterococcus genera dominate the microbiota of silage obtained from ryegrass harvested at three different harvests. In addition, the BK group had the highest abundance of Lactiplantibacillus plantarum (58.66%), and the CK group had the highest abundance of Enterococcus faecalis (42.88%). The most annotated metabolites among the differential metabolites of different harvests were peptides, and eight amino acids were dominant in the composition of the identified peptides. In the ryegrass silage, arginine, alanine, aspartate, and glutamate biosynthesis had the highest enrichment ratio in the metabolic pathway of KEGG pathway enrichment analysis. Valyl-isoleucine and glutamylvaline were positively correlated with Lactiplantibacillus plantarum. D-Pipecolic acid and L-glutamic acid were positively correlated with Levilactobacillus brevis. L-phenylalanyl-L-proline, 3,4,5-trihydroxy-6-(2-methoxybenzoyloxy) oxane-2-carboxylic acid, and shikimic acid were negatively correlated with Levilactobacillus brevis. In conclusion, this study explains the effects of different harvest frequencies on the fermentation quality, microbial community, and metabolites of ryegrass, and improves our understanding of the ensiling mechanisms associated with different ryegrass harvesting frequencies.

Deposit-feeding of Nonionellina labradorica (foraminifera) from an Arctic methane seep site and possible association with a methanotroph

Abstract. Several foraminifera are deposit feeders that consume organic detritus (dead particulate organic material with entrained bacteria). However, the role of such foraminifera in the benthic food web remains understudied. Foraminifera feeding on methanotrophic bacteria, which are 13C-depleted, may cause negative cytoplasmic and/or calcitic δ13C values. To test whether the foraminiferal diet includes methanotrophs, we performed a short-term (20 h) feeding experiment with Nonionellina labradorica from an active Arctic methane-emission site (Storfjordrenna, Barents Sea) using the marine methanotroph Methyloprofundus sedimenti and analysed N. labradorica cytology via transmission electron microscopy (TEM). We hypothesised that M. sedimenti would be visible post-experiment in degradation vacuoles, as evidenced by their ultrastructure. Sediment grains (mostly clay) occurred inside one or several degradation vacuoles in all foraminifers. In 24 % of the specimens from the feeding experiment degradation vacuoles also contained bacteria, although none could be confirmed to be the offered M. sedimenti. Observations of the apertural area after 20 h incubation revealed three putative methanotrophs, close to clay particles, based on bacterial ultrastructural characteristics. Furthermore, we noted the absence of bacterial endobionts in all examined N. labradorica but confirmed the presence of kleptoplasts, which were often partially degraded. In sum, we suggest that M. sedimenti can be consumed via untargeted grazing in seeps and that N. labradorica can be generally classified as a deposit feeder at this Arctic site.

Characteristics and particularities of bacterial community variation in the offshore shellfish farming waters of the North Yellow Sea

Bacteria in coastal waters drive global biogeochemical cycling and are strongly related to coastal environmental safety. The bacterial community in offshore shellfish farming waters of North China has its own characteristics and particularities, while the knowledge is limited. In this study, the bacterial community characteristics, the particularities of bacterial community in the waters with surface cold patches (SCPs) and the variation of pathogenic bacteria were investigated in the offshore shellfish farming waters in the North Yellow Sea (NYS) from 2017 to 2019. For all studied samples, Desulfobacterales acted as the keystone species taxon in microbial co-occurrence networks, and the proportional abundance of Actinobacteriota was found to be as low as 1.3%. The abundance of Marinobacter and Synechococcus was remarkably prominent in 13 genera with nitrogen-transforming function. The top two different bacterial functions in the spatial analysis (between the waters with SCPs and the ambient waters) were xenobiotics biodegradation and metabolism and metabolism of cofactors and vitamins, which were same with that in the seasonal analysis (between spring and summer). The abundance differences of most pathogenic bacteria analyzed in this study (11 out of 12 genera) also had the same variation dynamics between the spatial analysis and the seasonal analysis. An ANN predictive model for Vibrio abundance was constructed for Vibrio forecasting, with acceptable predictive accuracy. According to the above results, the bacterial community in the shellfish aquaculture waters in this study was characterized by the enhancing ability of nitrogen removal. Temperature was concluded as the predominant environmental factor to drive the variation of bacterial community function and pathogenic bacteria patterns in the offshore shellfish farming waters with SCPs. The results of this study will further our understanding of the bacterial community characteristics in offshore shellfish farming waters, and help for Vibrio forecasting and coastal environmental safety in aquaculture seawater.

Indoor microplastics and bacteria in the atmospheric fallout in urban homes

Humans may be exposed to microplastics (MPs) through food, drink, and air. Although several studies have examined indoor environmental MPs, none have yet compared atmospheric MP and bacterial deposition characteristics among rooms in homes. We investigated indoor airborne MPs and bacteria in five room types (bedroom, dining room, living room, bathroom, and study) based on the duration of usage of each room. We identified synthetic polymers (23,889 MP particles of 21 types) and bacterial communities (383 genera belong to 24 phyla) collected through atmospheric deposition in various rooms of 20 homes. The abundance and composition of MPs are related to the duration of usage, human activities, goods, cleanliness, and the composition of occupants (family members) in households. In addition, the homes of elderly families (age 68–81 years) showed higher bacterial concentrations than those of young families (age 28–35 years), indicating that age markedly affects the structure of household microbiota. Furthermore, a significant correlation between MP concentration and bacterial community structure was observed. The abundances of polyamide (PA), polyurethane (PU), and polyethylene (PE) showed positive correlations with the relative abundances of major bacterial phyla. Taken together, our results suggest that various rooms in the home exhibit distinct MP abundances and bacterial structures that may be affected by age, cleanliness, and human activities.

The pollutant elimination performance and bacterial communities of unpowered baffle rural sewage reactor filtered with construction wastes

Sewage and construction waste in rural areas are urgently needed to be effectively treated with low cost as the higher environmental demand and lower economic level in rural areas. In this study, unpowered baffle rural sewage reactors filtered with different construction wastes, autoclaved aerated concrete (ALC), composite mortar (CM), and red brick (RB), were established and operated to achieve the cooperative governance of rural sewage and rural construction wastes. The pollutant removal effect and bacterial communities were revealed and the mechanism of pollutant removal caused by construction wastes was discussed. Unpowered baffle rural sewage reactors filtered with construction wastes had evident removal effect on COD (31.57%–55.07%) and SS (27.57%–41.36%) during the 3 h retention time and cement based construction wastes (ALC and CM) showed evident TP removal effect (16.71%–35.26%). The bacterial communities of construction wastes (e.g. Chlorobium, Comamonas, and Acinetobacter) were complex and differed with waste type. However, the pollutant removal related functions of the bacteria on different construction wastes were similar. The different pollutant removal effect of construction wastes was mainly caused by their physicochemical characteristics, but not their bacterial community characteristics. ALC and RB can be used to COD removal, CM can be used to SS removal, and ALC and CM can be used to TP removal in rural sewage treatment. Overall, this study provided an effectively and low-cost method to co-governance of rural sewage and rural construction wastes which is suitable for rural areas and has development potential.

Large-scale microbiome analysis reveals bacterial community characteristics in typical Chinese herbal slices

Chinese herbal slices (CHSs) are closely associated to microorganisms, whether they are endophytic or epiphytic in plants, or introduced during processing. In this study, the structures and predicted functions of microbial communities in 150 batches of samples from five types of CHSs were investigated by combining pure culture and 16 S rDNA amplicon sequencing. Bile-salt-tolerant gram-negative bacteria were detected in 56.0% of samples, and Salmonella was detected in two batches of Glycyrrhiza slices and in one batch of Rheum slices. The main genera from the Enterobacteriaceae, Bacillaceae, Fibrobacteraceae, and Pseudomonadaceae families were assessed in typical colonies. Amplicon sequencing identified 1200 bacterial genera, including some pharmacopeial-controlled bacteria and many beneficial endophytes of medicinal plants. Around 65% of the genera co-occurred in all five CHSs. In clustering based on different algorithms, the samples from each CHS type were relatively clustered, with some overlap. Ranked from highest to lowest diversity, the CHSs were Rheum, Angelica, Astragalus, Codonopsis, and Glycyrrhiza. Each CHS had its indicator species. Functional annotations suggest that potential microbial transformation uses CHSs as substrates and microbial communities as transformants. Overall, it was demonstrated that, based on their complementary advantages, high-throughput sequencing technology and traditional pure-culture technology together can fully assess the microbial load of CHSs and reduce the misdetection rate. We observed large microbial communities in typical CHSs, demonstrating differences and similarities among different CHS types. These results provide a reference for establishing new microbial limit criteria for CHSs and highlight the importance of further correlating CHS microbial community structure and function.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11756-022-01199-0.

Succession of the Bacterial Communities and Functional Characteristics in Sheep Manure Composting.

Simple SummaryThe conversion of livestock manure into organic fertilizer through composting is an effective way to harmlessly and resourcefully utilize manure. The bacterial communities change rapidly during the composting process, and there is a synergistic effect of various bacteria, which realizes the dynamic fermentation of composting. However, the succession of bacterial communities and its relationship with the physicochemical properties of the material during sheep manure composting remain unclear. In this study, high-throughput sequencing technology and bioinformatics tools were used to analyze the succession and to explore the metabolic functions of bacterial communities during sheep manure composting. The results will help to further improve the sheep manure composting process, improve the quality of compost products, and promote fertilizer utilization of sheep manure.Bacterial community is a key factor affecting aerobic composting, and understanding bacterial community succession is important to revealing the mechanism of organic matter degradation. In this study, the succession and metabolic characteristics of bacterial communities were explored in 45 days composting of sheep manure and wheat straw by using high-throughput sequencing technology and bioinformatics tools, respectively. Results showed that the alpha diversity of bacterial community significantly decreased in the thermophilic (T2) phase and then recovered gradually in the bio-oxidative (T3) and the maturation (T4) phases. Bacterial communities varied at different stages, but there were 158 genera in common bacterial species. Unclassified_f_Bacillaceae, Oceanobacillus, Bacillus, Pseudogracilibacillus, and Nocardiopsis were identified as keystone bacterial genera. Eleven genera were significantly correlated (p < 0.05), or even extremely significantly correlated (p < 0.001), with the physicochemical factors. Redundancy analysis (RDA) showed that changes of bacterial community diversity correlated with physicochemical factors. The highest relative abundances were amino acid and carbohydrate metabolism among the metabolic groups in the compost. These results will provide theoretical support for further optimizing sheep manure composting conditions and improving the quality of organic fertilizers.

Effects of dietary non-fibrous carbohydrate (NFC) to neutral detergent fiber (NDF) ratio change on rumen bacterial community and ruminal fermentation parameters in Chinese black Tibetan sheep (Ovis aries)

This study evaluated the effects of different non-fibrous carbohydrate/neutral detergent fiber (NFC/NDF) ratios on the rumen fermentation parameters and bacterial community of black Tibetan sheep. Fifteen 2-month-old rams with an average body weight of 10.45 ± 0.96 kg were randomly assigned to three treatments and fed NFC/NDF of 1.82 (H group), 1.16 (M group), and 0.71 (L group), respectively. This study was conducted for 127 d, including 7 d of adaption to the diets. The fermentation parameters and bacterial characteristics of rumen fluid were measured after the end of feeding trials. According to the results, the concentrations of propionate and total volatile fatty acids (TVFA) increased in the H group than those in the L group (P < 0.05), while the concentration of acetate was highly increased in the L group (P < 0.05). A total of 1463 OTUs were obtained with 97% consistency. Both phylum Bacteroidetes and Firmicutes were dominant bacterial phyla. Proteobacteria accounted for a significantly higher proportion of bacteria in the L group than in the H and M groups (P < 0.05). At the genus level, the main cellulose-degrading bacteria, such as Prevotella_1, Prevotellaceae UCG-003 and Ruminococcus_1 possessed a higher relative abundance in dietary NFC/NDF ratio of 0.71 (P < 0.05). Correlation analysis revealed that the abundance of Patesicbacteria was negatively associated with TVFA, whereas the abundance of Bacteroidetes was positively associated with TVFA. Using clusters of orthologous groups (COG), the functions of the rumen microbial community were mainly enrichment in amino acid metabolism and carbohydrate metabolism. In summary, ruminal bacterial community composition and fermentation characteristics were altered under different dietary NFC/NDF ratios in black Tibetan sheep.

Association between Escherichia coli with NotI-restriction resistance and urinary tract infections.

Escherichia coli is the most common cause of urinary tract infections (UTIs). It is widely accepted that uropathogenic E. coli (UPEC) mainly emerge from the distal gut microbiota. Identification of bacterial characteristics that are able to differentiate UPEC from fecal commensal strains will facilitate the development of novel strategies to detect and monitor the spread of UPEC. Fifty fecal commensal, 83 UTI-associated and 40 biliary tract infection (BTI)-associated E. coli isolates were analyzed. The NotI restriction patterns of chromosomal DNA in the isolates were determined by pulse-field gel electrophoresis. The phylogenetic types and the presence of 9 known virulence genes of each isolate were determined by PCR analyses. Additionally, the susceptibilities of the isolates to antibiotics were revealed. Then the associations of NotI resistance with UTI-associated isolates, phylotypes, and antibiotic resistance were assessed. NotI resistance was correlated with UTI-associated isolates, compared to the fecal isolates. Consistently, NotI-resistant isolates harbored a greater number of virulence factors and mainly belonged to phylotype B2. Additionally NotI resistance was correlated with chloramphenicol resistance among the bacteria. Among the fecal, UTI-associated and BTI-associated groups, the distribution of NotI-resistant group B2 isolates was correlated with UTI-associated bacteria. NotI resistance alone is a potential marker for distinguishing fecal strains and UPEC, while the combination of NotI resistance and B2 phylogeny is a candidate marker to differentiate UPEC from fecal and other extraintestinal pathogenic E. coli. Additionally, NotI resistance may be valuable for assessing the potential of chloramphenicol resistance of E. coli.

Analysis of recurrent urinary tract infection (UTI) in University Hospital – approach of antibiotic resistance in clinical isolates

The fifty-two bacteria were isolated from urinary tract infections in University Hospital in Sumaré, São Paulo State, Brazil. These isolates were analyzed about their antibiotic resistance and their bacterial characteristics. Around percentage from these isolates were identified as belonging to Escherichia coli strains, followed by Klebsiella pneumoniae and Pseudomonas aeruginosa. The multiresistance profile (resistance profile major than four 4 antibiotic classes) were viewed in thirteen (13) strains of Escherichia coli, sixteen (16) strains in Klebsiella pneumoniae (being two (2) carbapenem resistant suggesting an existence of KPC strain). The results had demonstrated an indiscriminate antibiotic use concentrated in the increase of quinolones resistance (principally in ciprofloxacin use), and also the rise of KPC super bacteria.

Metagenome Analysis of the Bacterial Characteristics in Invasive Klebsiella Pneumoniae Liver Abscesses.

Background Klebsiella pneumoniae liver abscess (KPLA) combined with extrahepatic migratory infection (EMI) is defined as invasive KPLA (IKPLA) and is associated with a poor prognosis. The mechanism of IKPLA formation is yet to be elucidated. In this study, metagenomic sequencing was used to compare the bacterial characteristics between IKPLA and KPLA to explore the underlying mechanism of invasiveness.MethodsClinical details, imaging, and microbial features were retrospectively evaluated by medical record review. Metagenomic sequencing was performed on the pus samples of liver abscesses whose culture results were indicative of monomicrobial Klebsiella pneumoniae (K. pneumoniae). Bacterial diversity and composition in IKPLA and KPLA were comparatively analyzed, and the key pathways and genes that may affect invasiveness were further explored.ResultsSixteen patients were included in this study. Five patients with EMI were included in the IKPLA group, and the other eleven patients without EMI were assigned to the KPLA group. There was no statistical difference in the hypermucoviscous phenotype and serotype of K. pneumoniae between the two groups. The bacterial diversity of IKPLA was lower than that of KPLA. The abundant taxa in the IKPLA group were primarily species of unclassified Enterobacteriaceae and K. pneumoniae. The KPLA group had a high abundance of the genera Tetrasphaera and Leuconostoc. Metabolic pathway genes represented most of the enriched genes in IKPLA. Fourteen pathogenic genes with significant differences in abundance were identified between the two groups, including ybtS, fepC, phoQ, acrB, fimK, magA, entC, arnT, iucA, fepG, oqxB, entA, tonB, and entF (p < 0.001).ConclusionThe diversity and bacterial composition of IKPLA were significantly different from those of KPLA. Microbiological changes in the abscess, activation of the related metabolic pathways, and the pathogenic gene expression may constitute a novel mechanism that regulates the invasiveness of KPLA.

Relationship between Bacterial Contribution and Self-Healing Effect of Cement-Based Materials.

The civil research community has been attracted to self-healing bacterial-based concrete as a potential solution in the economy 4.0 era. This concept provides more sustainable material with a longer lifetime due to the reduction of crack appearance and the need for anthropogenic impact. Regardless of the achievements in this field, the gap in the understanding of the importance of the bacterial role in self-healing concrete remains. Therefore, understanding the bacterial life cycle in the self-healing effect of cement-based materials and selecting the most important relationship between bacterial contribution, self-healing effect, and material characteristics through the process of microbiologically (bacterially) induced carbonate precipitation is just the initial phase for potential applications in real environmental conditions. The concept of this study offers the possibility to recognize the importance of the bacterial life cycle in terms of application in extreme conditions of cement-based materials and maintaining bacterial roles during the self-healing effect.

The effect of fermentation conditions (temperature, salt concentration, and pH) with lactobacillus strains for producing Short Chain Fatty Acids

Short-Chain Fatty Acids are one of the vital metabolites generated by the fermentation of dietary fiber in the gastrointestinal tract through bacterial fermentation and play an essential role in human health. This a study aimed to evaluate the effects of different fermentation conditions, including temperature (30, 42 °C), salt concentrations (2, 4 and 6%), pH (4.5, 5 and 6), and their interaction effects on the production of short-chain fatty acids (acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid) by Lactobacillus fermentum ATCC 9338, Lactobacillus fermentum 19SH and Lactobacillus acidophilus ATCC 4356. Once grown under different fermentation conditions, supernatants and pellets of fermentation media were separated, and then SCFAs were measured using Gas chromatography/mass spectrometry (GC-MS). Results revealed that fatty acid content was altered in each fermentation condition, and the highest amount after lactic acid belonged to propionic acid. Accordingly, Lb. Fermentum 19sh, Lb. Fermentum ATCC9938, and Lb. Acidophilus ATCC4356 produced the highest levels of isovaleric acid, acetic acid, propionic acid, isobutyric acid, butyric acid, and valeric acids, respectively. The results indicated a relationship between the production of short-chain fatty acids and the growth of bacterial strains and cell membrane characteristics.

Dormancy induced by oxidative damage during disinfection facilitates conjugation of ARGs through enhancing efflux and oxidative stress: A lagging response

Disinfection is known to greatly alter bacterial characteristics in water, and high horizontal gene transfer (HGT) frequency occurs in eutrophic conditions. Interestingly, these two seemingly irrelevant phenomena were closely linked by a lagging response of the increased conjugation frequency probably via daily water disinfection in this study. Three disinfection methods (UV, chlorine, and UV/chlorine) were selected to investigate the increased frequency of conjugation of ARGs during the stage of continuing culture after disinfection. The results showed that the conjugative transfer frequency was inhibited for all disinfection treatments after 24 h of co-incubation. Unexpectedly, after 3–7 days of co-cultivation, the HGT frequencies were increased by 2.71–5.61-fold and 5.46–13.96-fold in chlorine (30 min) and UV/chlorine (1 min) groups compared to the control, but not in UV-irradiated groups. A neglected lagging response was found for the first time, i.e., oxidative disinfection-induced dormancy promotes conjugative transfer of ARGs. Furthermore, mechanistic insights were gained from (1) membrane permeability, (2) conjugation-regulated system, (3) efflux pump system, and (4) oxidative stress system, suggesting the critical role of enhancing efflux and oxidative stress in the propagation of ARGs. Finally, the known instantaneous effect of oxidation disinfection was compared to address the controversial debate in this research field, proposing that the dormancy level of donor bacteria is the key to evaluating whether it can promote the HGT process. This study has important environmental implications for elucidating the transmission of ARGs after oxidation disinfection.

Human Blood Bacteriome: Eubiotic and Dysbiotic States in Health and Diseases.

The human gut microbiome is acknowledged as being associated with homeostasis and the pathogenesis of several diseases. Conventional culture techniques are limited in that they cannot culture the commensals; however, next-generation sequencing has facilitated the discovery of the diverse and delicate microbial relationship in body sites and blood. Increasing evidence regarding the blood microbiome has revolutionized the concept of sterility and germ theory in circulation. Among the types of microbial communities in the blood, bacteriomes associated with many health conditions have been thoroughly investigated. Blood bacterial profiles in healthy subjects are identified as the eubiotic blood bacteriome, whereas the dysbiotic blood bacteriome represents the change in bacterial characteristics in subjects with diseases showing deviations from the eubiotic profiles. The blood bacterial characteristics in each study are heterogeneous; thus, the association between eubiotic and dysbiotic blood bacteriomes and health and disease is still debatable. Thereby, this review aims to summarize and discuss the evidence concerning eubiotic and dysbiotic blood bacteriomes characterized by next-generation sequencing in human studies. Knowledge pertaining to the blood bacteriome will transform the concepts around health and disease in humans, facilitating clinical implementation in the near future.

Inflammation and Gastric Cancer.

Gastric cancer remains a major killer globally, although its incidence has declined over the past century. It is the fifth most common cancer and the third most common reason for cancer-related deaths worldwide. Gastric cancer is the outcome of a complex interaction between environmental, host genetic, and microbial factors. There is significant evidence supporting the association between chronic inflammation and the onset of cancer. This association is particularly robust for gastrointestinal cancers in which microbial pathogens are responsible for the chronic inflammation that can be a triggering factor for the onset of those cancers. Helicobacter pylori is the most prominent example since it is the most widespread infection, affecting nearly half of the world’s population. It is well-known to be responsible for inducing chronic gastric inflammation progressing to atrophy, metaplasia, dysplasia, and eventually, gastric cancer. This review provides an overview of the association of the factors playing a role in chronic inflammation; the bacterial characteristics which are responsible for the colonization, persistence in the stomach, and triggering of inflammation; the microbiome involved in the chronic inflammation process; and the host factors that have a role in determining whether gastritis progresses to gastric cancer. Understanding these interconnections may improve our ability to prevent gastric cancer development and enhance our understanding of existing cases.