Bacterial Characteristics Research Articles

Response of Algal–Bacterial Regrowth Characteristics to the Hypochlorite in Landscape Ponds Replenished with Reclaimed Water

Sodium hypochlorite was widely used as a supplementary disinfectant in reclaimed water (RW) production during the COVID-19 epidemic. It is well known that the chlorination of RW results in a relatively high bacterial regrowth potential in pipeline systems. However, the algal growth and algal–bacterial interactions would be another concern in RW-replenished surface water with light irradiation. In this study, microcosmic experiments were used to explore the impact of hypochlorite on the algae–bacteria community, including the influence of hypochlorite on algal–bacterial regrowth, microbial community structure, and the specific bacteria that can survive chlorination. Results demonstrated that algal growth potential could be promoted after chlorination of the RW, and bacteria abundance increased along with an increase in algal density, which is probably related to DOM decomposition by chlorine oxidation. Additionally, the characteristics of the bacterial community were altered. It is more likely that phytospheric bacteria will survive chlorination. It was discovered that the secondary risks of chlorine disinfection include the growth of algae in addition to bacterial regeneration, which is an extension of the common perception. As a consequence, when chlorinated reclaimed water is used as a supplement for urban landscape ponds, particular attention should be paid to controlling bio-available organic matter induced by reactive chlorine, as well as the algal bloom, to decrease the risk of pathogen transmission.

The Effect of Bacteria on the Stability of Microfluidic-Generated Water-in-Oil Droplet.

Microencapsulation in emulsion droplets has great potential for various applications such as food which require formation of highly stable emulsions. Bacterial-emulsion interactions affect the physiological status of bacteria while bacterial cell characteristics such as surface-active properties and metabolic activity can affect emulsion stability. In this study, the viability and growth of two different bacterial species, Gram-negative Escherichia coli and Gram-positive Lactobacillus paracasei, encapsulated in water-in-oil (W/O) droplets or as planktonic cells, were monitored and their effect on droplet stability was determined. Microencapsulation of bacteria in W/O droplets with growth media or water was achieved by using a flow-focusing microfluidic device to ensure the production of highly monodispersed droplets. Stability of W/O droplets was monitored during 5 days of storage. Fluorescence microscopy was used to observe bacterial growth behaviour. Encapsulated cells showed different growth to planktonic cells. Encapsulated E. coli grew faster initially followed by a decline in viability while encapsulated L. paracasei showed a slow gradual growth throughout storage. The presence of bacteria increased droplet stability and a higher number of dead cells was found to provide better stability due to high affinity towards the interface. The stability of the droplets is also species dependent, with E. coli providing better stability as compared to Lactobacillus paracasei.

PhoD-harboring bacterial community composition dominates organic P mineralization under long-term P fertilization in acid purple soil.

A better understanding of the regulatory role of microorganisms on soil phosphorous (P) mobilization is critical for developing sustainable fertilization practices and reducing P resource scarcity. The phoD genes regulate soil organic P (Po) mobilization. Based on the long-term P application experiments in acid purple soil of maize system in Southwest China (started in 2010), the experiment included five P levels: 0, 16, 33, 49, and 65.5 kg P hm-2 (P0, P16, P33, P49, and P65.5, respectively). The molecular speciation of organic P in soil was determined by 31P-nuclear magnetic resonance (NMR), high-throughput sequencing technology, and real-time qPCR were used to analyze the bacterial community and abundance of phoD-harboring bacterial genes, exploring the bacterial community and abundance characteristics of phoD gene and its relationship with the forms of Po and alkaline phosphatase (ALP) activity in the soil. The results showed that the orthophosphate monoesters (OM) were the main Po speciation and varied by P fertilization in acid purple soil. ALP activity decreased as P fertilization increased. Co-occurrence network analysis identified the overall network under five P fertilizations. The keystone taxon base on the network showed that Collimonas, Roseateles, Mesorhizobium, and Cellulomonas positively correlated with both OM and Po. The random forest showed that Cellulomonas, Roseateles, and Rhodoplanes were the key predictors for ALP activity. The keystone taxon was a more important predictor than the dominant taxon for ALP, OM, and Po. The structural equation model (SEM) showed that soil organic matter (SOM), available P (AP), and OM were the main factors influencing the ALP by reshaping phoD-harboring bacteria alpha diversity, community composition, and phoD abundance. The phoD-harboring bacterial community composition especially the keystone taxon rather than alpha diversity and abundance dominated the ALP activity, which could promote P utilization over an intensive agroecosystem. These findings improve the understanding of how long-term gradient fertilization influences the community composition and function of P-solubilizing microorganisms in acid purple soil.

The effect of a spontaneous induction prophage, phi458, on biofilm formation and virulence in avian pathogenic Escherichia coli.

Prophage sequences are present in most bacterial genomes and account for up to 20% of its host genome. Integration of temperate phages may have an impact on the expression of host genes, while some prophages could turn into the lytic cycle and affect bacterial host biological characteristics. We investigated the role of spontaneous induction prophages in avian pathogenic Escherichia coli (APEC), which is the causative agent of avian colibacillosis in poultry, and considered a potential zoonotic bacterium related to the fact it serves as an armory of extraintestinal pathogenic E. coli. We found that APEC strain DE458 had a high spontaneous induction rate in vivo and in vitro. The released phage particles, phi458, were isolated, purified, and sequenced, and the deletion mutant, DE458Δphi458, was constructed and characterized. Biofilm formation of DE458Δphi458 was strongly decreased compared to that of the wild-type strain (p < 0.01). In addition, while the addition of DNase (100 μg/ml) did not affect prophage release but could digest eDNA, it significantly reduced the biofilm production of DE458 biofilm to a level close to that of DE458Δphi458. Compared to DE458, the adhesion and invasion abilities of DE458Δphi458 increased by approximately 6-20 times (p < 0.05). The virulence of DE458Δphi458 was enhanced by approximately 10-fold in chickens based on a 50% lethal dose. Furthermore, avian infection assays showed that the bacterial loads of DE458Δphi458 in the lung and liver were increased by 16.5- and 10-fold (p < 0.05), respectively, compared with those of the WT strain. The qRT-PCR revealed that deletion of phi458 led to upregulation of type I fimbriate-related gene fimH and curli-related gene csgC by 3- and 2.8-fold, respectively (p < 0.01). Our study revealed that phi458 promoted biofilm formation by spontaneously inducing and decreasing virulence by repressing virulence genes.

Effects of surfactant on Bacillus mucilaginosus adsorption characteristics during vanadium bioleaching process

Bioleaching is a sustainable and economical technology for extracting valuable elements from low-grade ores or refractory resources. Adsorption of bacteria on mineral surface is the usual basic condition for the deep interaction between bacteria and minerals, thereby improving the bioleaching efficiency of target elements. The addition of surfactants in bioleaching process is an efficient and promising method for improving the bacteria adsorption on mineral surface. Therefore, effects of surfactant SDS (Sodium Dodecyl Sulfate) on bacterial adsorption characteristics were investigated during the bioleaching process from vanadium-bearing shale by Bacillus mucilaginosus (B.M). The optimal vanadium bioleaching conditions were 0.5 g/L of SDS, 2 g/L of yeast dip powder, and 7.0 of the initial pH. The B.M adsorption equilibrium on the surface of the vanadium-bearing shale with and without addition of surfactant SDS fitted a Freundlich equation, and the addition of surfactant SDS could significantly enhance the B.M absorption on the vanadium-bearing shale. The Pseudo-first-order adsorption kinetics was more suitable to be selected for the demonstration of the B.M adsorption on the surface of the vanadium-bearing shale with and without addition of surfactant SDS, and the addition of surfactant SDS could accelerate the B.M adsorption rate on the surface of the vanadium-bearing shale.

Changes in the Physical, Chemical, and Bacterial Community Characteristics of Soil in Response to Short-Term Combined Organic–Inorganic Fertilizers in a Dry Direct-Seeded Paddy Field

Dry direct-seeded rice cultivation is a simple and labor-saving planting method wherein the combined application of organic and inorganic fertilizers can improve yield. However, the effects of combined fertilizers on soil properties and bacteria in dry direct-seeded rice paddy soil are unclear. Here, four treatments, conventional fertilization (NPK), seaweed bio-organic fertilizer + NPK, Jishiwang bio-organic fertilizer + NPK, and attapulgite organic fertilizer + NPK applied for three consecutive years were tested to explore their effects on soil physical, chemical, and bacterial community characteristics in a dry direct-seeded rice paddy field. The combined fertilizers increased alkaline hydrolysis-nitrogen and available potassium while decreasing the bulk density and pH; in addition, a marked increase in the relative abundance of soil macroaggregates (&gt;5 mm) and clay particles and a decrease in that of sand was observed. Urease and neutral phosphatase activities were the highest with the Jishiwang organic fertilizer + NPK, whereas invertase and catalase activities were the highest with attapulgite organic fertilizer + NPK. All combined fertilizers considerably increased the bacterial richness index (ACE) and Chao index; Jishiwang bio-organic fertilizer + NPK also increased the Simpson index, whereas the seaweed bio-organic fertilizer + NPK reduced it. Proteobacteria and Acidobacteria accounted for 54.25–70.49% of the total bacterial relative abundance. The relative abundance of Verrucomicrobia, Chloroflexi, Firmicutes, and Nitrospirae increased with the combined fertilizers. The correlation network analysis showed predominant antagonistic relationships. A redundancy analysis demonstrated that total nitrogen, soil organic matter, urease, and invertase were the main environmental factors affecting bacterial composition. Combined fertilizers may improve soil physical and chemical properties, fertility, and bacterial richness.

Effect of Mangrove on Nitrogen Removal in the Intertidal Zone of Shenzhen’s Deep Bay: From 15N Isotope Tracing to Microbial Analysis

This study focuses on the nitrogen removal capability of the mangrove wetland system towards resolving the excessive inorganic nitrogen content in the marine water of Shenzhen’s Deep Bay. The nitrogen distribution characteristics, biological nitrogen removal processes, nitrogen removal functional genes, and bacterial community characteristics were investigated in five wetland sites in the intertidal zone of the Deep Bay, viz. the Kandelia candel, Bruguiera gymnorrhiza, Sonneratia apetala, Aegiceras corniculatum, and mud flat sites. The results showed that ammonia and nitrate in the marine water were significantly removed in the five wetlands sites, with respective removal efficiencies of 70.9–75.5% and 89.5–94.0%. The concentration of ammonia and nitrate in pore water remained significantly unchanged with depth. Denitrification and anammox were each system’s main biological nitrogen removal processes, and their rates were 1.70–3.22 and 0.07–0.36 μmol/(kg·h), respectively. The denitrification rates in the mangroves were higher than in the mud flat site, unlike the anammox rates. The denitrifying functional genes (nirS, nosZ) and anammox functional gene (hzsB) showed an excellent linear relationship with the relevant process rates. Bacillus and Pseudomonas were the main heterotrophic denitrifying bacteria genera identified. The autotrophic denitrifying bacteria genus Sulfurovum was also identified in the systems, while Candidatus Scalindua was the only anammox genus identified in this study. The results of this study improve our understanding of the nitrogen removal characteristics of coastal wetlands and the role of mangrove plants in the biological nitrogen removal processes.

The difference between drainage channels and sewers in rural areas: from sewage quality to bacterial characteristics.

Channels and sewers are commonly used to collect sewage during extensively rural areas. The sewage and bacterial characteristics of rural sewage collection systems can influence their operation and maintenance performance which further affect appropriate system decision. In this study, eight rural sewage collection systems (four each of channels and sewers) were applied to evaluate the sewage quality, bacterial characteristics, and their differences of two kinds of collection systems. The results indicate that significantly distinction existed between the rural sewage collection systems of channels and sewers. Sewage in channels had higher suspended solid (SS) concentration but lower sulfide concentration than that in sewers. The SS, sulfate, and chemical oxygen demand (COD) removal capacity in channels was nearly 3.5, 4.0, and 0.6 times than those in sewers. At least 14 genera and 18 species of bacteria showed significantly distinction between channels and sewers even their main phylum, genus, and species of bacteria communities was Proteobacteria (∼70.3%), Acinetobacter (∼22.3%), and Pseudomonas fragi (∼13.8%), respectively. The structural characteristics and bacterial function caused the difference between channels and sewers. Overall, this study revealed the intrinsic and essential differences of channels and sewers, providing basic and meaningful data for rural sewage collection systems decision.

MicroRNAs associated with the pathogenesis and their role in regulating various signaling pathways during Mycobacterium tuberculosis infection.

Despite more than a decade of active study, tuberculosis (TB) remains a serious health concern across the world, and it is still the biggest cause of mortality in the human population. Pathogenic bacteria recognize host-induced responses and adapt to those hostile circumstances. This high level of adaptability necessitates a strong regulation of bacterial metabolic characteristics. Furthermore, the immune reponse of the host virulence factors such as host invasion, colonization, and survival must be properly coordinated by the pathogen. This can only be accomplished by close synchronization of gene expression. Understanding the molecular characteristics of mycobacterial pathogenesis in order to discover therapies that prevent or resolve illness relies on the bacterial capacity to adjust its metabolism and replication in response to various environmental cues as necessary. An extensive literature details the transcriptional alterations of host in response to in vitro environmental stressors, macrophage infection, and human illness. Various studies have recently revealed the finding of several microRNAs (miRNAs) that are believed to play an important role in the regulatory networks responsible for adaptability and virulence in Mycobacterium tuberculosis. We highlighted the growing data on the existence and quantity of several forms of miRNAs in the pathogenesis of M. tuberculosis, considered their possible relevance to disease etiology, and discussed how the miRNA-based signaling pathways regulate bacterial virulence factors.

Identification and characterization of bacteria isolated from patients with cystic fibrosis in Jordan

Background Notable emergence of multidrug-resistant bacteria has become increasingly problematic worldwide. Most patients with cystic fibrosis (CF) suffer from chronic persistent infections with frequent occurrence of acute exacerbations. Routine screening of bacterial strains, epidemiological characteristics, and resistance patterns are particularly useful for patient management and maintenance of infection control procedures Methods In this study, 43 pharyngeal samples were taken from patients with CF. Microbiological bacterial culture and identification, antimicrobial susceptibility testings, biofilm formation, including minimum biofilm eradication concentration (MBEC) and PCR for detecting resistance genes were performed. Results All samples were positive for bacterial growth. The predominant species were Staphylococcus aureus (41.86%; n = 18) and Pseudomonas aeruginosa (39.53%; n = 17). 30% of isolated bacteria were multidrug-resistant, resisting high concentrations of tested antibiotics. Among the 42 biofilm-forming isolates, 23.8% (n = 10) were strong biofilm formers. The occurance of resistance genes varied with blaKPC detected in 71% (n = 17) of all Gram-negative isolates and mecA found in 61% (n = 11) of all S. aureus strains. Conclusions The majority of isolated bacteria were S. aureus and P. aeruginosa. The high frequency of antimicrobial resistance, the presence of resistance genes, and biofilm formation highlight the challenge in treatment and infection control measures in patients with CF. KEY MESSAGES Staphylococcus aureus and Pseudomonas aeruginosa are the most prevalent pathogens found in patients with CF in Jordan. Detection of antimicrobial resistance genes in patients with CF confirms that antimicrobial resistance patterns must always be monitored. Biofilm formation significantly increases the tolerance of bacteria to antimicrobial agents.

Machine learning to predict the development of recurrent urinary tract infection related to single uropathogen, Escherichia coli

Recurrent urinary tract infection (RUTI) can damage renal function and has impact on healthcare costs and patients’ quality of life. There were 2 stages for development of prediction models for RUTI. The first stage was a scenario in the clinical visit. The second stage was a scenario after hospitalization for urinary tract infection caused by Escherichia coli. Three machine learning models, logistic regression (LR), decision tree (DT), and random forest (RF) were built for the RUTI prediction. The RF model had higher prediction accuracy than LR and DT (0.700, 0.604, and 0.654 in stage 1, respectively; 0.709, 0.604, and 0.635 in stage 2, respectively). The decision rules constructed by the DT model could provide high classification accuracy (up to 0.92 in stage 1 and 0.94 in stage 2) in certain subgroup patients in different scenarios. In conclusion, this study provided validated machine learning models and RF could provide a better accuracy in predicting the development of single uropathogen (E. coli) RUTI. Both host and bacterial characteristics made important contribution to the development of RUTI in the prediction models in the 2 clinical scenarios, respectively. Based on the results, physicians could take action to prevent the development of RUTI.

Virulence, phenotype and genotype characteristics of invasive group B Streptococcus isolates obtained from Swedish pregnant women and neonates

Group B streptococci (GBS) are bacteria that can cause preterm birth and invasive neonatal disease. Heterogeneous expression of virulence factors enables GBS to exist as both commensal bacteria and to become highly invasive. A molecular epidemiological study comparing GBS bacterial traits, genotype and host characteristics may indicate whether it is possible to predict the risk of perinatal invasive GBS disease and more accurately target intrapartum antibiotic prophylaxis. A total of 229 invasive GBS isolates from Swedish pregnant women or neonates were assessed for virulence and phenotypic traits: hemolysis zone, hemolytic pigment (Granada agar), Streptococcus B Carrot Broth (SBCB) assay, CAMP factor, and hyaluronidase activity. Genes regulating hemolytic pigment synthesis (covR/covS, abx1, stk1, stp1) were sequenced. Of the virulence factors and phenotypes assessed, a Granada pigment or SBCB score ≥ 2 captured more than 90% of EOD isolates with excellent inter-rater reliability. High enzyme activity of hyaluronidase was observed in 16% (36/229) of the invasive GBS isolates and notably, in one case of stillbirth. Hyaluronidase activity was also significantly higher in GBS isolates obtained from pregnant/postpartum individuals versus the stillbirth or neonatal invasive isolates (p < 0.001). Sequencing analysis found that abx1 (g.T106I), stk1 (g.T211N), stp1 (g.K469R) and covS (g.V343M) variants were present significantly more often in the higher (Granada pigment score ≥ 2) versus lower pigmented isolates (p < 0.001, each variant). Among the 203 higher Granada pigment scoring isolates, 22 (10.8%) isolates had 3 of the four sequence variants and 10 (4.9%) had 2 of the four sequence variants. Although heterogeneity in GBS virulence factor expression was observed, the vast majority were more highly pigmented and contained several common sequence variants in genes regulating pigment synthesis. High activity of hyaluronidase may increase risk for stillbirth and invasive disease in pregnant or postpartum individuals. Our findings suggest that testing for GBS pigmentation and hyaluronidase may, albeit imperfectly, identify pregnant people at risk for invasive disease and represent a step towards a personalized medical approach for the administration of intrapartum antibiotic prophylaxis.

Characteristics of Bacterial Community in Pelteobagrus fulvidraco Integrated Multi-Trophic Aquaculture System

Pelteobagrus fulvidraco integrated multi-trophic aquaculture system (YPS) is a new ecological culture system of Pelteobagrus fulvidraco. In this manuscript, we used high throughput sequencing technology and the water analysis method to analyze the bacterial community characteristics of YPS and the water environment, respectively. The results showed that the concentration of total nitrogen (1.47~1.84 mg/L) and total phosphorus (0.14~0.18 mg/L) reached the discharge standard of freshwater pond aquaculture water, and the concentrations of ammonia (0.10~0.95 mg/L) and nitrite (3.85~6.68 μg/L) were lower than those in traditional ponds, which was suitable for the growth of Pelteobagrus fulvidraco. At the phylum level, Actinobacteria (35.68%), Firmicutes (24.58%), Proteobacteria (23.49%) and Bacteroidetes (6.59%) were the dominant phyla. The abundance of genus had obvious seasonal variation characteristics. In spring (April), Limnohabitans (8.01%) was the dominant genus; in early summer (June), Exiguobacterium (23.44%), Planococcus (22.27%), Paenisporosarcina (16.81%) and Planomicrobium (5.85%) were the dominant genera; at the end of summer (August), hgcI_clade (21.84%) and CL500_29_marin_group (4.61%) were the dominant genera; compared with the end of summer, the dominant genera Sporichthyaceae (11.31%) and Sediminibacterium (3.32%) were newly added in autumn (October). The dominant genera in different periods were correlated with dissolved oxygen, water temperature and nitrogen nutrients. With the accumulation of nitrogen nutrients in water, the abundance of metabolic pathways in the bacterial community increased, and the abundance of infectious and immune disease pathways increased. This study provides a theoretical basis for the regulation of YPS.

Meandering development of tidal creeks splits bacterial communities and functional characteristics: Evidence from a field study in Jiangsu Coast, China

Tidal creeks are common and important geomorphic features in intertidal zones, which provide a broad range of ecosystem services. The meandering development of tidal creeks can cause a discrepancy in sediment properties between the two banks in tidal creek bends, which affects a few geomorphic and biological processes and seems to be another incentive for the ecological effects of tidal creeks. However, how this discrepancy affects the distribution of bacterial communities in tidal creek bends remains unclear. To this end, we collected sediment samples from a typical tidal creek bend in Jiangsu Coast, China. The bacterial communities were characterized by 16S rRNA gene sequencing and the sediment properties were determined. Results showed that bacterial communities and their functions exhibited significant differences between the convex bank (VB) and the concave bank (CB). Bacterial diversity was higher in VB than in CB, mainly attributed to higher nutrients (TOC and TN), moisture, and finer sediment in VB. The oligotrophic (e.g., Chloroflexi), drought-resistant (e.g., Actinobacteria), and mobile (e.g. Nitrospirae) bacteria had higher abundances in CB. In contrast, bacteria with opposite niche preferences (e.g., Proteobacteria and Acidobacteria) tended to inhabit VB. Network analysis revealed that CB bacterial communities had a higher efficiency of nutrient cycling and carbon uptake but were more vulnerable to environmental disturbances. FAPROTAX results showed that bacterial functions associated with carbon cycles were more abundant in CB, whereas those associated with nitrogen and sulfur cycles were more abundant in VB. Overall, these results demonstrate that the meandering development of tidal creeks splits bacterial communities and functional characteristics in tidal creeks bends. These findings are expected to provide useful information for further understanding and predicting the ecological effects of tidal creeks.

Cloning and characterization of Aiia, an acylhomoserine lactonase from Bacillus cereus RC1 to control soft rot causing pathogen Lelliottia amnigena RCE.

Bacterial pathogenesis-associated characteristics such as biofilm formation, synthesis of hydrolyzing enzymes, and toxins are regulated by Acyl Homoserine Lactones (AHLs), small peptides and diffusing signal factors (DSF). Lelliottia amnigena is gram negative bacteria and its pathogenicity is regulated by the luxR andluxIclass of quorum sensing. The signaling molecules and their concentrations are essential for the virulence of the pathogenic bacterium. To suppresses the pathogenicity; the concentration of signalling molecules must be controlled or degraded. The lactonase have the ability to hydrolyze lactonesof different chain length. The present study deals with a newer approach to control the pathogenesis of Lelliottia amnigena through isolation and characterization of Aiia lactonase from Bacillus cereus RC1. Aiia lactonase specific primers were used to amplify the gene, and the sequence thus obtained was submitted to the Genbank database under accession # OK643884.1. The gene was cloned in pBE-S shuttle vector and transformed in the recombinant host. The expressed and purified protein had a molecular weight of 28.00 KDa and exhibited its optimum activity at 37℃ by inhibiting the violacein pigment of the monitor strain Chromobacterium violaceum MTCC 2656. The proteinaceous nature of the purified molecule was confirmed by incubating it in the presence of proteinase K for 1h. The activity of the pathogenesis-related protein, polygalacturonase was drastically reduced in the presence of the purified Aiia protein. The purified protein also showed a zone of inhibition when plated together with Lelliottia amnigena RCE (MZ712952.1). Searches of the Conserved Domain Database suggested that this protein belonged to the Metallo-beta-lactamase superfamily and is closely related to Aiia from B. thuringiensis serovar kurstaki. Modeling of the protein structure was done using I-TASSER; a C-score of 0.55 suggested that the model was of good quality. To be used commercially, this recombinant protein needs to be purified at an industrial scale; it can then be used to repress the growth of soft rot causing bacteria in horticultural crops during their storage period.

Effect of Lactic Acid Bacteria on Bacterial Community Structure and Characteristics of Sugarcane Juice.

Fermentation technology is of great significance for food preservation; through fermentation, while extending the shelf life of food, it can also improve the sensory quality of food and increase its nutritional value. Compared with natural fermentation, the use of specific microorganisms for fermentation can be used to determine the direction of fermentation. Therefore, in order to better explore the effect of bacterial community structure on the quality of sugarcane juice naturally fermented and inoculated with different lactic acid bacteria in the fermentation process, the most suitable method for sugarcane juice fermentation was found, which provided a theoretical basis for the safe production of fermented sugarcane juice. In this experiment, the sugarcane juice was treated differently and divided into four groups: natural fermentation, fermentation with Lactobacillus HNK10, fermentation with Lactococcus HNK21, and HNK10 + HNK21 compound fermentation. The changes in bacterial community structure of different treatments of sugarcane juice during fermentation were analyzed by high-throughput sequencing technology, and the quality change of different treatments of sugarcane juice during fermentation was analyzed by high-performance liquid chromatography, and the change in its bacteriostatic ability was explored. The results showed that after the sugarcane juice treated with Lactobacillus HNK10 was fermented at 37 °C for 48 h, the final fermented sugarcane juice had a large abundance of lactic acid bacteria and high-quality and strong antibacterial activity. Conclusions: changes in the bacterial community structure during the fermentation of sugarcane juice affect the formation of organic acids and the change of bacteriostatic ability and directly determine the quality and shelf life of fermented sugarcane juice.

Long-term excessive application of K2SO4 fertilizer alters bacterial community and functional pathway of tobacco-planting soil.

To improve tobacco leaf quality, excessive K2SO4 fertilizers were applied to soils in major tobacco-planting areas in China. However, the effects of K2SO4 application on soil microbial community and functions are still unclear. An eight-year field experiment with three kinds of K2SO4 amounts (low amount, K2O 82.57 kg hm-2, LK; moderate amount, K2O 165.07 kg hm-2, MK; high amount, K2O 247.58 kg hm-2, HK) was established to assess the effects of K2SO4 application on the chemical and bacterial characteristics of tobacco-planting soil using 16S rRNA gene and metagenomic sequencing approaches. Results showed that HK led to lower pH and higher nitrogen (N), potassium (K), sulfur(S) and organic matter contents of the soil than LK. The bacterial community composition of HK was significantly different from those of MK and LK, while these of MK and LK were similar. Compared to LK, HK increased the relative abundance of predicted copiotrophic groups (e.g. Burkholderiaceae, Rhodospirillaceae families and Ellin6067 genus) and potentially beneficial bacteria (e.g. Gemmatimonadetes phylum and Bacillus genus) associated with pathogens and heavy metal resistance, N fixation, dissolution of phosphorus and K. While some oligotrophic taxa (e.g. Acidobacteria phylum) related to carbon, N metabolism exhibited adverse responses to HK. Metagenomic analysis suggested that the improvement of pathways related to carbohydrate metabolism and genetic information processing by HK might be the self-protection mechanism of microorganisms against environmental stress. Besides, the redundancy analysis and variation partitioning analysis showed that soil pH, available K and S were the primary soil factors in shifting the bacterial community and KEGG pathways. This study provides a clear understanding of the responses of soil microbial communities and potential functions to excessive application of K2SO4 in tobacco-planting soil.

Effects of nonthermal dielectric barrier discharge plasma against Listeria monocytogenes and quality of smoked salmon fillets

AbstractThe objective was to explore the effects of dielectric barrier discharge (DBD) plasma on bacterial reduction, physiological characteristics (pH and moisture), and sensorial quality against Listeria monocytogenes on the surface of smoked salmon. Reductions were treated with 5, 10, 20, 30, 40, 50, and 60 min with DBD plasma varied from 0.17, 0.25, 0.32, 0.70, 0.81, 1.05, and 1.25 log10 CFU/g, respectively. The R2 and D‐value of L. monocytogenes was .98 and 49.01 min, respectively. However, moisture levels were significantly different after 30 and 60 min of treatment compared with the control but pH and the sensory qualities were not. This study found that treated with 60 min DBD plasma reduced L. monocytogenes by more than 90% without negatively affecting the smoked salmon. Based on these results, antibacterial treatment for smoked salmon, and this strategy could be explored in the seafood industry to increase food safety.

High-Energy-Density Organic Amendments Enhance Soil Health.

Soil microbial biomass (SMB) and soil microbial communities (SMCs) are the key factors in soil health and agricultural sustainability. We hypothesized that low bioavailable carbon (C) and energy were the key limiting factors influencing soil microbial growth and developed a new fertilization system to address this: the simultaneous application of mineral fertilizers and high-energy-density organic amendments (HED-OAs). A microcosm soil incubation experiment and a Brassica rapa subsp. chinensis pot culture experiment were used to test the effects of this new system. Compared to mineral fertilizer application alone, the simultaneous input of fertilizers and vegetable oil (SIFVO) achieved a bacterial abundance, fungal abundance, and fungal:bacterial ratio that were two orders of magnitude higher, significantly higher organic C and nitrogen (N) content, significantly lower N loss, and nearly net-zero N2O emissions. We proposed an energy and nutrient threshold theory to explain the observed bacterial and fungal growth characteristics, challenging the previously established C:N ratio determination theory. Furthermore, SIFVO led to microbial community improvements (an increased fungal:bacterial ratio, enriched rhizosphere bacteria and fungi, and reduced N-transformation bacteria) that were beneficial for agricultural sustainability. A low vegetable oil rate (5 g/kg) significantly promoted Brassica rapa subsp. chinensis growth and decreased the shoot N content by 35%, while a high rate caused severe N deficiency and significantly inhibited growth of the crop, confirming the exceptionally high microbial abundance and indicating severe microbe–crop competition for nutrients in the soil.

Impact of tumoral structure and bacterial species on growth and biodistribution of live bacterial therapeutics in xenografted tumours

Live bacterial therapeutics is gaining attention, especially for cancer therapy, because anaerobic bacteria selectively grow inside the solid tumours. However, the effect of tumour structure and bacterial characteristics on the pharmacokinetics of tumours is unclear; therefore, we aimed to elucidate the effects of tumour structure and types of bacteria on tumoral bacterial growth. Using six mouse xenograft models, including stroma-rich tumours similar to clinical tumours, and two models of live bacterial therapeutics, Salmonella typhimurium VNP20009 and Escherichia coli DH5α, we investigated bacterial growth and distribution in tumours after intravenous administration. Rapid growth of E. coli was observed in HCT116 and other tumours with few collagens, blood vessels not covered by mural cells, and a cancer cell area proliferated disorderly, whereas tumours with contrasting features, such as BxPC-3, showed lower bacterial growth and a limited intratumor distribution. Alternatively, Salmonella typhimurium VNP20009, when successfully proliferated (the probability was approximately 50%), grew to 108 colony forming units/g tissue even in BxPC-3 tumours, and its intratumor distribution was extensive. This study suggests that the development of new methods to modify tumour structure will be essential for the development of anti-tumour clinical therapies based on live bacterial therapeutics.