M1 Strain Research Articles

Identification of four Armillaria strains and their effects on quality and yield of Gastrodia elata f. glauca

In order to improve the quality and yield of Gastrodia elata f. glauca,determine the suitable Armillaria strains for the accompanying experiment in Xiaocaoba,Yiliang,four Armillaria strains were selected. They were used for G. elata cultivation,and the gene sequence,r DNA-ITS,β-tubulin and EF1-α of four Armillaria strains,were compared and analyzed. The yield was mesured in November which was based on previous laboratory research. The tubers were washed and steamed,then dried and powdered. The content of gastrodin and p-hydroxybenzyl alcohol was determined by UPLC,the polysaccharide was determined by phenol-concentrated sulfuric acid method. The results showed that the strains M1,M2,M3 and M4 were Armillaria gallica group but there were differences in the yield and active ingredient content when they were cultivated with the same G. elata. The yield of G. elata( Jian Ma) was the lowest when cultivated with Armillaria strain M3,but it was not the same when used M1,0. 981 kg·m-2,the highest yield in the four stains.The content of gastrodin was 0. 581%,the total content of gastrodin and p-hydroxybenzyl alcohol was 0. 595%,when accompanied with M1 strains. It was higher than other strains. The content of G. elata polysaccharide was 2. 132%,which was similar to the content of M3 strain,higher than that of M2 and M4 strain. Selecting phylogenesis of Armillaria strians,the content of active ingredient,and the yield as indicators,it was concluded concerned that the M1 strain was the best of four strains. The results will provide a theoretical basis and guidance for higher yield and quality in cultivation of G. elata in Yiliang.

Transcriptomic and metabolic analysis of an astaxanthin-hyperproducing Haematococcus pluvialis mutant obtained by low-temperature plasma (LTP) mutagenesis under high light irradiation

Haematococcus pluvialis can accumulate sufficient levels of astaxanthin under various stress conditions. High light irradiation is essential for astaxanthin accumulation in Haematococcus pluvialis. However, a lack of genomic information limits the understanding of its physiological metabolism for high astaxanthin production. In this work, we investigated the wild-type (WT) strain and mutant strain (named as M3 which was obtained in our previous work) under high light irradiation and compared the difference in astaxanthin biosynthesis. We collected and analyzed the data of de novo transcriptome information of Haematococcus pluvialis at 24 h under high light stress. Our transcriptomic results indicated that M3 strain had higher utilization efficiency of CO2 to provide the precursors of carotenoid and fatty acid biosynthesis by increasing the expression levels of phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), malate dehydrogenase (ME), ribulose bisphosphate carboxylase/oxygenase (Rubisco) activase (RCA) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) while decreasing the expression levels of fructose-1, 6-bisphosphatase (FBP). The analysis of pigments, chlorophyll fluorescence and the quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that M3 strain maintained higher photosynthetic activity by regulating chlororespiration pathway and elevating non-photosynthetic pigment (lutein, β-carotene, and astaxanthin) content to alleviate photooxidative damage. Moreover, the M3 strain showed higher fatty acid content than the WT strain. Overall, combinative analysis of de novo transcriptomic and physiological data provided information necessary for not only a better understanding of the difference in astaxanthin biosynthesis between WT and M3 strains but also the feasibility of genetic engineering of Haematococcus pluvialis in the future.

Thermosensitive pilus production by FCT type 3 Streptococcus pyogenes controlled by Nra regulator translational efficiency.

Summary Streptococcus pyogenes produces a diverse variety of pili in a serotype‐dependent manner and thermosensitive expression of pilus biogenesis genes was previously observed in a serotype M49 strain. However, the precise mechanism and biological significance remain unclear. Herein, the pilus expression analysis revealed the thermosensitive pilus production only in strains possessing the transcriptional regulator Nra. Experimental data obtained for nra deletion and conditional nra‐expressing strains in the background of an M49 strain and the Lactococcus heterologous expression system, indicated that Nra is a positive regulator of pilus genes and also highlighted the importance of the level of intracellular Nra for the thermoregulation of pilus expression. While the nra mRNA level was not significantly influenced by a temperature shift, the Nra protein level was concomitantly increased when the culture temperature was decreased. Intriguingly, a putative stem‐loop structure within the coding region of nra mRNA was a factor related to the post‐transcriptional efficiency of nra mRNA translation. Either deletion of the stem‐loop structure or introduction of silent chromosomal mutations designed to melt the structure attenuated Nra levels, resulting in decreased pilus production. Consequently, the temperature‐dependent translational efficacy of nra mRNA influenced pilus thermoregulation, thereby potentially contributing to the fitness of nra‐positive S. pyogenes in human tissues.

Effects of Temperature on the Ability of Metabolites from Permafrost Microorganisms to Activate the Synthesis of Systemic Cytokines by Mononuclear Cells.

The effects of metabolites of Bacillus sp. strain M3 and Bacillus megaterium strain 8/75-1 isolated from permafrost formations, as well as a medicinal Bacillus cereus strain IP5832 on the secretion of TNFα, IL-1β, and IL-10 by mononuclear cells of human peripheral blood depending on the temperature of bacteria culturing (-16oC, -5oC, and 42oC) were studied. Metabolites of 8/75-1 and M3 strains cultured at 42oC produced more potent stimulating effect on TNFα and IL-10 synthesis than metabolites from these bacteria cultured at -16oC and -5oC (p<0.01). Temperature did not affect the ability of metabolites to modulate IL-1β synthesis in all bacterial strains and the ability of IP5832 strain metabolites to modulate TNFα production. IL-10 secretion was minimum under the effect of metabolites of IP5832 strain cultured at 42oC. The TNFα/IL-10 and IL-1β/IL-10 ratios indicated that metabolites of permafrost bacteria cultured at 42oC can shift the balance towards the synthesis of proinflammatory cytokines.

Reducing Viral Inhibition of Host Cellular Apoptosis Strengthens the Immunogenicity and Protective Efficacy of an Attenuated HSV-1 Strain.

Herpes simplex virus 1 (HSV-1), a member of α herpesviruses, shows a high infectivity rate of 30%-60% in populations of various ages. Some herpes simplex (HSV) vaccine candidates evaluated during the past 20years have not shown protective efficacy against viral infection. An improved understanding of the immune profile of infected individuals and the associated mechanism is needed. HSV uses an immune evasion strategy during viral replication, and various virus-encoded proteins, such as ICP47 and Vhs, participate in this process through limiting the ability of CD8+ cytotoxic T lymphocytes to recognize target cells. Other proteins, e.g., Us3 and Us5, also play a role in viral immune evasion via interfering with cellular apoptosis. In this work, to study the mechanism by which HSV-1 strain attenuation interferes with the viral immune evasion strategy, we constructed a mutant strain, M5, with deletions in the Us3 and Us5 genes. M5 was shown to induce higher neutralizing antibody titers and a stronger cellular immune response than our previously reported M3 strain, and to prevent virus infection more effectively than the M3 strain in an in vivo mouse challenge test.

Treatment of Primary and Secondary Domestic Wastewater Effluents by using Microalga Oscillatoria Sp

The scarcity of water all around the world been increasing and has resulted in the development of new water reuse technologies. But, the success of water reuse projects have not been so effective and also with so many disadvantages. Hence Laboratory-scale experiments were performed to develop a procedure for biological treatment of secondary and tertiary wastewater treatment using microalgae. Ten microalgae strains were isolated from Munnakal beach, Kerala and were identified through microscopic examination. Then, the ability of microalgae to remove nutrients and organic carbon from primary and secondary effluents were investigated. Among the isolated strains, M1 strain alone showed maximum reductions in soluble concentrations total nitrogen, phosphorus, and COD (27%, 91.7%, 88.6% and 25.5. 30.8%), in both for primary and secondary wastewater respectively. The high nutrient removal capacity of the M1(Oscillatoria sp.,) microalgae suggests that these microalgae have the potential to be used for tertiary treatment and treatment of side streams at treatment plants under simple and inexpensive operational conditions. Therefore, a microalgae-based treatment system can reduce or eliminate the need for chemical disinfection methods. The results of this study indicate that microalgae-based treatment systems can be incorporated in treatment plants in a very simple and inexpensive way without the need for providing CO2, nutrients, heating, pH adjustment, etc.

Biological Impact of a Large-Scale Genomic Inversion That Grossly Disrupts the Relative Positions of the Origin and Terminus Loci of the Streptococcus pyogenes Chromosome.

A large-scale genomic inversion encompassing 0.79 Mb of the 1.816-Mb-long Streptococcus pyogenes serotype M49 strain NZ131 chromosome spontaneously occurs in a minor subpopulation of cells, and in this report genetic selection was used to obtain a stable lineage with this chromosomal rearrangement. This inversion, which drastically displaces the ori site relative to the terminus, changes the relative length of the replication arms so that one replichore is approximately 0.41 Mb while the other is about 1.40 Mb in length. Genomic reversion to the original chromosome constellation is not observed in PCR-monitored analyses after 180 generations of growth in rich medium. Compared to the parental strain, the inversion surprisingly demonstrates a nearly identical growth pattern in the first phase of the exponential phase, but differences do occur when resources in the medium become limited. When cultured separately in rich medium during prolonged stationary phase or in an experimental acute infection animal model (Galleria mellonella), the parental strain and the invertant have equivalent survival rates. However, when they are coincubated together, both in vitro and in vivo, the survival of the invertant declines relative to the level for the parental strain. The accompanying aspect of the study suggests that inversions taking place near oriC always happen to secure the linkage of oriC to DNA sequences responsible for chromosome partition. The biological relevance of large-scale inversions is also discussed.IMPORTANCE Based on our previous work, we created to our knowledge the largest asymmetric inversion, covering 43.5% of the S. pyogenes genome. In spite of a drastic replacement of origin of replication and the unbalanced size of replichores (1.4 Mb versus 0.41 Mb), the invertant, when not challenged with its progenitor, showed impressive vitality for growth in vitro and in pathogenesis assays. The mutant supports the existing idea that slightly deleterious mutations can provide the setting for secondary adaptive changes. Furthermore, comparative analysis of the mutant with previously published data strongly indicates that even large genomic rearrangements survive provided that the integrity of the oriC and the chromosome partition cluster is preserved.

Remarkable Genome Stability among emm1 Group A Streptococcus in Belgium over 19 Years.

During the last two decades, there has been a public health concern of severe invasive infections caused by Group A Streptococcus (GAS) of the emm1 genotype. This study investigated the dynamics of emm1 GAS during 1994–2013 in Belgium. emm1 GAS isolated from blood, tissue, and wounds of patients with invasive infections (n = 23, S1–S23), and from patients with uncomplicated pharyngitis (n = 15, NS1–NS15) were subjected to whole-genome mapping (WGM; kpn) (Opgen). Whole-genome sequencing was performed on 25 strains (WGS; S1–S23 and NS6–NS7) (Illumina Inc.). Belgian GAS belonged to the M1T1 clone typified by the 36-kb chromosomal region encoding extracellular toxins, NAD+-glycohydrolase and streptolysin O. Strains from 1994–1999 clustered together with published strains (MGAS5005 and M1476). From 2001 onward, invasive GAS showed higher genomic divergence in the accessory genome and harbored on average 7% prophage content. Low evolutionary rate (2.49E-008; P > 0.05) was observed in this study, indicating a highly stable genome. The studied invasive and pharyngitis isolates were no genetically distinct populations based on the WGM and core genome phylogeny analyses. Two copies of the speJ superantigen were present in the 1999 and 2010 study strains (n = 3), one being chromosomal and one being truncated and associated with phage remnants.This study showed that emm1 GAS in Belgium, compared with Canada and UK M1 strains, were highly conserved by harboring a remarkable genome stability over a 19-year period with variations observed in the accessory genome.

Conserved and specific features of Streptococcus pyogenes and Streptococcus agalactiae transcriptional landscapes

BackgroundThe human pathogen Streptococcus pyogenes, or group A Streptococcus, is responsible for mild infections to life-threatening diseases. To facilitate the characterization of regulatory networks involved in the adaptation of this pathogen to its different environments and their evolution, we have determined the primary transcriptome of a serotype M1 S. pyogenes strain at single-nucleotide resolution and compared it with that of Streptococcus agalactiae, also from the pyogenic group of streptococci.ResultsBy using a combination of differential RNA-sequencing and oriented RNA-sequencing we have identified 892 transcription start sites (TSS) and 885 promoters in the S. pyogenes M1 strain S119. 8.6% of S. pyogenes mRNAs were leaderless, among which 81% were also classified as leaderless in S. agalactiae. 26% of S. pyogenes transcript 5′ untranslated regions (UTRs) were longer than 60 nt. Conservation of long 5′ UTRs with S. agalactiae allowed us to predict new potential regulatory sequences. In addition, based on the mapping of 643 transcript ends in the S. pyogenes strain S119, we constructed an operon map of 401 monocistrons and 349 operons covering 81.5% of the genome. One hundred fifty-six operons and 254 monocistrons retained the same organization, despite multiple genomic reorganizations between S. pyogenes and S. agalactiae. Genomic reorganization was found to more often go along with variable promoter sequences and 5′ UTR lengths. Finally, we identified 117 putative regulatory RNAs, among which nine were regulated in response to magnesium concentration.ConclusionsOur data provide insights into transcriptome evolution in pyogenic streptococci and will facilitate the analysis of genetic polymorphisms identified by comparative genomics in S. pyogenes.

A Controlled Human Infection Model of Group A Streptococcus Pharyngitis: Which Strain and Why?

Group A Streptococcus (GAS) is a major cause of global infection-related morbidity and mortality. A modern controlled human infection model (CHIM) of GAS pharyngitis can accelerate vaccine development and pathogenesis research. A robust rationale for strain selection is central to meeting ethical, scientific, and regulatory requirements. Multifaceted characterization studies were done to compare a preferred candidate emm75 (M75) GAS strain to three other strains: an alternative candidate emm12 (M12) strain, an M1 strain used in 1970s pharyngitis CHIM studies (SS-496), and a representative (5448) of the globally disseminated M1T1 clone. A range of approaches were used to explore strain growth, adherence, invasion, delivery characteristics, short- and long-term viability, phylogeny, virulence factors, vaccine antigens, resistance to killing by human neutrophils, and lethality in a murine invasive model. The strains grew reliably in a medium without animal-derived components, were consistently transferred using a swab method simulating the CHIM protocol, remained viable at -80°C, and carried genes for most candidate vaccine antigens. Considering GAS molecular epidemiology, virulence factors, in vitro assays, and results from the murine model, the contemporary strains show a spectrum of virulence, with M75 appearing the least virulent and 5448 the most. The virulence profile of SS-496, used safely in 1970s CHIM studies, was similar to that of 5448 in the animal model and virulence gene carriage. The results of this multifaceted characterization confirm the M75 strain as an appropriate choice for initial deployment in the CHIM, with the aim of safely and successfully causing pharyngitis in healthy adult volunteers.IMPORTANCE GAS (Streptococcus pyogenes) is a leading global cause of infection-related morbidity and mortality. A modern CHIM of GAS pharyngitis could help to accelerate vaccine development and drive pathogenesis research. Challenge strain selection is critical to the safety and success of any CHIM and especially so for an organism such as GAS, with its wide strain diversity and potential to cause severe life-threatening acute infections (e.g., toxic shock syndrome and necrotizing fasciitis) and postinfectious complications (e.g., acute rheumatic fever, rheumatic heart disease, and acute poststreptococcal glomerulonephritis). In this paper, we outline the rationale for selecting an emm75 strain for initial use in a GAS pharyngitis CHIM in healthy adult volunteers, drawing on the findings of a broad characterization effort spanning molecular epidemiology, in vitro assays, whole-genome sequencing, and animal model studies.

Gene fitness landscape of group A streptococcus during necrotizing myositis.

Necrotizing fasciitis and myositis are devastating infections characterized by high mortality. Group A streptococcus (GAS) is a common cause of these infections, but the molecular pathogenesis is poorly understood. We report a genome-wide analysis using serotype M1 and M28 strains that identified GAS genes contributing to necrotizing myositis in nonhuman primates (NHP), a clinically relevant model. Using transposon-directed insertion-site sequencing (TraDIS), we identified 126 and 116 GAS genes required for infection by serotype M1 and M28 organisms, respectively. For both M1 and M28 strains, more than 25% of the GAS genes required for necrotizing myositis encode known or putative transporters. Thirteen GAS transporters contributed to both M1 and M28 strain fitness in NHP myositis, including putative importers for amino acids, carbohydrates, and vitamins and exporters for toxins, quorum-sensing peptides, and uncharacterized molecules. Targeted deletion of genes encoding 5 transporters confirmed that each isogenic mutant strain was significantly (P < 0.05) impaired in causing necrotizing myositis in NHPs. Quantitative reverse-transcriptase PCR (qRT-PCR) analysis showed that these 5 genes are expressed in infected NHP and human skeletal muscle. Certain substrate-binding lipoproteins of these transporters, such as Spy0271 and Spy1728, were previously documented to be surface exposed, suggesting that our findings have translational research implications.

Fitness genes of group A streptococci in necrotizing fasciitis and myositis.

Necrotizing fasciitis and myositis caused by group A streptococci (GAS) are among the most fulminating infections, with a mortality rate of 20% to 30%. Although numerous regimens have been utilized in attempts to control these devastating infections, such as combinations of various antimicrobial agents and intravenous immunoglobulin (IVIG) as well as hyperbaric oxygen therapy, none have been the complete answer. Zhu and colleagues have utilized a transposon-directed insertion-site sequencing (TraDIS) protocol to identify 126 genes of M1 and 116 genes of M28 strains of GAS required for myositis, of which 25% encode transporters, which could be used as possible targets for future therapeutic protocols.

Hypervirulent group A Streptococcus emergence in an acaspular background is associated with marked remodeling of the bacterial cell surface.

Inactivating mutations in the control of virulence two-component regulatory system (covRS) often account for the hypervirulent phenotype in severe, invasive group A streptococcal (GAS) infections. As CovR represses production of the anti-phagocytic hyaluronic acid capsule, high level capsule production is generally considered critical to the hypervirulent phenotype induced by CovRS inactivation. There have recently been large outbreaks of GAS strains lacking capsule, but there are currently no data on the virulence of covRS-mutated, acapsular strains in vivo. We investigated the impact of CovRS inactivation in acapsular serotype M4 strains using a wild-type (M4-SC-1) and a naturally-occurring CovS-inactivated strain (M4-LC-1) that contains an 11bp covS insertion. M4-LC-1 was significantly more virulent in a mouse bacteremia model but caused smaller lesions in a subcutaneous mouse model. Over 10% of the genome showed significantly different transcript levels in M4-LC-1 vs. M4-SC-1 strain. Notably, the Mga regulon and multiple cell surface protein-encoding genes were strongly upregulated–a finding not observed for CovS-inactivated, encapsulated M1 or M3 GAS strains. Consistent with the transcriptomic data, transmission electron microscopy revealed markedly altered cell surface morphology of M4-LC-1 compared to M4-SC-1. Insertional inactivation of covS in M4-SC-1 recapitulated the transcriptome and cell surface morphology. Analysis of the cell surface following CovS-inactivation revealed that the upregulated proteins were part of the Mga regulon. Inactivation of mga in M4-LC-1 reduced transcript levels of multiple cell surface proteins and reversed the cell surface alterations consistent with the effect of CovS inactivation on cell surface composition being mediated by Mga. CovRS-inactivating mutations were detected in 20% of current invasive serotype M4 strains in the United States. Thus, we discovered that hypervirulent M4 GAS strains with covRS mutations can arise in an acapsular background and that such hypervirulence is associated with profound alteration of the cell surface.

Phosphatase activity of the control of virulence sensor kinase CovS is critical for the pathogenesis of group A streptococcus.

The control of virulence regulator/sensor kinase (CovRS) two-component system is critical to the infectivity of group A streptococcus (GAS), and CovRS inactivating mutations are frequently observed in GAS strains causing severe human infections. CovS modulates the phosphorylation status and with it the regulatory effect of its cognate regulator CovR via its kinase and phosphatase activity. However, the contribution of each aspect of CovS function to GAS pathogenesis is unknown. We created isoallelic GAS strains that differ only by defined mutations which either abrogate CovR phosphorylation, CovS kinase or CovS phosphatase activity in order to test the contribution of CovR phosphorylation levels to GAS virulence, emergence of hypervirulent CovS-inactivated strains during infection, and GAS global gene expression. These sets of strains were created in both serotype M1 and M3 backgrounds, two prevalent GAS disease-causing serotypes, to ascertain whether our observations were serotype-specific. In both serotypes, GAS strains lacking CovS phosphatase activity (CovS-T284A) were profoundly impaired in their ability to cause skin infection or colonize the oropharynx in mice and to survive neutrophil killing in human blood. Further, response to the human cathelicidin LL-37 was abrogated. Hypervirulent GAS isolates harboring inactivating CovRS mutations were not recovered from mice infected with M1 strain M1-CovS-T284A and only sparsely recovered from mice infected with M3 strain M3-CovS-T284A late in the infection course. Consistent with our virulence data, transcriptome analyses revealed increased repression of a broad array of virulence genes in the CovS phosphatase deficient strains, including the genes encoding the key anti-phagocytic M protein and its positive regulator Mga, which are not typically part of the CovRS transcriptome. Taken together, these data establish a key role for CovS phosphatase activity in GAS pathogenesis and suggest that CovS phosphatase activity could be a promising therapeutic target in GAS without promoting emergence of hypervirulent CovS-inactivated strains.

Biomass and lipid production of a novel freshwater thermo-tolerant mutant strain of Chlorella pyrenoidosa NCIM 2738 in seawater salinity recycled medium

Micro-algae have significant potential for the production of biofuel. It has been previously shown that existing processes of producing micro-algal biofuels are not yet economically viable at commercial scale. Fundamentally, this process will require the implementation of inexpensive harvesting methods and productive algal strains that are tolerant to harsh conditions. The use of freshwater in the large-scale cultivation of microalgae is currently unsustainable; hence, the studies which target the use of seawater medium can reduce the demand of freshwater. Chlorella pyrenoidosa has been extensively studied in freshwater. However, information on the cultivation of C. pyrenoidosa for growth productivity in recycled seawater medium, generated after harvesting through autoflocculation is scarce. In this context, the present study investigates the effect of nutrients sufficient seawater medium following reuse of nutrients exhausted seawater medium on the biochemical composition, biomass and lipid productivities of an in-house developed, thermotolerant strain of C. pyrenoidosa under high temperature (45 °C), outdoor culture conditions. The strain C. pyrenoidosa M18 was found to thrive in seawater medium resulting in increased biomass and lipid productivity. Lipid productivity in seawater medium exceeded 51 mg/Ld−1 which was nearly 2-fold greater than freshwater. Furthermore, the strain was able to grow well and autoflocculate at recycled seawater medium giving biomass and lipid productivities, respectively of 338 mgL−1d−1 and 66 mgL−1d−1. The dry cell weight comprised of 28–32% carbohydrate content when cultivated in recycled seawater medium. Additionally, exposure to high salinity led to an enhanced chlorophyll content as well as increased Fv/Fm ratio. The auto-flocculating property of thermotolerant C. pyrenoidosa M18 strain, in addition to the high biomass and lipid productivities in nutrient exhausted recycled seawater medium, make this microalga an excellent candidate for large-scale outdoor cultivation for biodiesel production.

A novel small RNA Bmsr1 enhances virulence in Brucella melitensis M28

Brucellosis, caused by Brucella spp., is one of the most serious zoonotic bacterial diseases. Small RNAs (sRNAs) are recognized as a key player in bacterial post-transcription regulation, since they participate in many biological processes with high efficiency and may govern the intracellular biochemistry and virulence of some pathogenic bacteria. Here, a novel small regulatory RNA, Bmsr1 (Brucella melitensis M28 small RNA 1), was identified in a virulent Brucella melitensis M28 strain based on bioinformatic analysis, reverse transcription PCR (RT-PCR), and Northern blot. The Bmsr1 expression level was highly induced after infection of macrophage cells RAW264.7 at 48 h, suggesting a role for Bmsr1 during in vitro infection. Indeed, bmsr1 deletion mutant of M28 attenuated its intracellular survival in RAW264.7 at 24 h and 48 h post-infection. In a mouse model of chronic infection, bmsr1 deletion strain displayed decreased colonization in the spleen while Bmsr1-overexpressed strain showed higher colonization levels than wild type pathogen. Isobaric tags for relative and absolute quantification (iTRAQ) revealed that 314 proteins were differentially expressed in M28Δbmsr1 compared with wild type. Functional annotation analysis demonstrated that most of those proteins are involved in biological processes and those proteins in the ribosome and nitrogen metabolism pathways were enriched. iTRAQ results combined with target prediction identified several potential target genes related to virulence, including virB2, virB9, virB10, virB11, and vjbR and many metabolism genes. Taken together, this study revealed the contribution of a novel sRNA Bmsr1 to virulence of B. melitensis M28, probably by influencing genes involved in T4SS, virulence regulator VjbR and other metabolism genes.

Human IgG Increases Virulence of Streptococcus pyogenes through Complement Evasion

Streptococcus pyogenes is an exclusively human pathogen that can provoke mild skin and throat infections but can also cause fatal septicemia. This gram-positive bacterium has developed several strategies to evade the human immune system, enabling S. pyogenes to survive in the host. These strategies include recruiting several human plasma proteins, such as the complement inhibitor, C4b-binding protein (C4BP), and human (hu)-IgG through its Fc region to the bacterial surface to evade immune recognition. We identified a novel virulence mechanism whereby IgG-enhanced binding of C4BP to five of 12 tested S. pyogenes strains expressed diverse M proteins that are important surface-expressed virulence factors. Importantly, all strains that bound C4BP in the absence of IgG bound more C4BP when IgG was present. Further studies with an M1 strain that additionally expressed protein H, also a member of the M protein family, revealed that binding of hu-IgG Fc to protein H increased the affinity of protein H for C4BP. Increased C4BP binding accentuated complement downregulation, resulting in diminished bacterial killing. Accordingly, mortality from S. pyogenes infection in hu-C4BP transgenic mice was increased when hu-IgG or its Fc portion alone was administered concomitantly. Electron microscopy analysis of human tissue samples with necrotizing fasciitis confirmed increased C4BP binding to S. pyogenes when IgG was present. Our findings provide evidence of a paradoxical function of hu-IgG bound through Fc to diverse S. pyogenes isolates that increases their virulence and may counteract the beneficial effects of IgG opsonization.

Molecular Characterisation of Virulent Gene vacA in Helicobacter pylori Clinical Isolates from Patients with Gastroduodenal Diseases in Assam, India

Background:Helicobacter pylori, the gastric bacterium, is widely known to be one of the most genetically diverse group of organisms whose pathogenesis as well as the diversity in infection outcome may be attributed to a variety of virulent genes. Aim: This study aimed to study the molecular profile of H. pylori vacA gene by determining the phylogenetic relatedness and genetic diversity of the strains isolated in this region with those of other geographical regions. Materials and Methods: A total of twenty H. pylori clinical strains were isolated from randomly selected 100 patients suffering from gastroduodenal diseases as well as endoscopically normal patients in a cross-sectional hospital-based setting from January 2016 to May 2017. VacA signal sequence and mid regions of H. pylori were amplified by polymerase chain reaction followed by DNA sequencing and phylogenetic analysis. Results:VacA s1m1 allelic variant was more prevalent in our study, regardless of the clinical outcomes. Phylogenetic analysis of VacA s1 strains revealed clustering of most of the strains. VacA m1 strains clustered with Bangladesh strains which is a country nearest to India. Conclusion: Prevalence of VacA s1m1 strains may account for high risk of transmission of this gastric pathogen and the overall risk of acquiring infection. Phylogenetic analysis results suggests the prevalence of high genetic diversity in our region. Our findings may aid in developing a better understanding of the genetic structure of H. pylori and the pathophysiology of associated diseases, thus facilitating the implementation of various treatment options.

A Glycine Riboswitch in Streptococcus pyogenes Controls Expression of a Sodium:Alanine Symporter Family Protein Gene.

Regulatory RNAs play important roles in the control of bacterial gene expression. In this study, we investigated gene expression regulation by a putative glycine riboswitch located in the 5′-untranslated region of a sodium:alanine symporter family (SAF) protein gene in the group A Streptococcus pyogenes serotype M49 strain 591. Glycine-dependent gene expression mediated by riboswitch activity was studied using a luciferase reporter gene system. Maximal reporter gene expression was observed in the absence of glycine and in the presence of low glycine concentrations. Differences in glycine-dependent gene expression were not based on differential promoter activity. Expression of the SAF protein gene and the downstream putative cation efflux protein gene was investigated in wild-type bacteria by RT-qPCR transcript analyses. During growth in the presence of glycine (≥1 mM), expression of the genes were downregulated. Northern blot analyses revealed premature transcription termination in the presence of high glycine concentrations. Growth in the presence of 0.1 mM glycine led to the production of a full-length transcript. Furthermore, stability of the SAF protein gene transcript was drastically reduced in the presence of glycine. We conclude that the putative glycine riboswitch in S. pyogenes serotype M49 strain 591 represses expression of the SAF protein gene and the downstream putative cation efflux protein gene in the presence of high glycine concentrations. Sequence and secondary structure comparisons indicated that the streptococcal riboswitch belongs to the class of tandem aptamer glycine riboswitches.

Chronic alcohol consumption alters transcriptional profiles and mucosal cytokine production of intestinal lamina propria lymphocytes

Micro-algae have significant potential for the production of biofuel. It has been previously shown that existing processes of producing micro-algal biofuels are not yet economically viable at commercial scale. Fundamentally, this process will require the implementation of inexpensive harvesting methods and productive algal strains that are tolerant to harsh conditions. The use of freshwater in the large-scale cultivation of microalgae is currently unsustainable; hence, the studies which target the use of seawater medium can reduce the demand of freshwater. Chlorella pyrenoidosa has been extensively studied in freshwater. However, information on the cultivation of C. pyrenoidosa for growth productivity in recycled seawater medium, generated after harvesting through autoflocculation is scarce. In this context, the present study investigates the effect of nutrients sufficient seawater medium following reuse of nutrients exhausted seawater medium on the biochemical composition, biomass and lipid productivities of an in-house developed, thermotolerant strain of C. pyrenoidosa under high temperature (45 °C), outdoor culture conditions. The strain C. pyrenoidosa M18 was found to thrive in seawater medium resulting in increased biomass and lipid productivity. Lipid productivity in seawater medium exceeded 51 mg/Ld−1 which was nearly 2-fold greater than freshwater. Furthermore, the strain was able to grow well and autoflocculate at recycled seawater medium giving biomass and lipid productivities, respectively of 338 mgL−1d−1 and 66 mgL−1d−1. The dry cell weight comprised of 28–32% carbohydrate content when cultivated in recycled seawater medium. Additionally, exposure to high salinity led to an enhanced chlorophyll content as well as increased Fv/Fm ratio. The auto-flocculating property of thermotolerant C. pyrenoidosa M18 strain, in addition to the high biomass and lipid productivities in nutrient exhausted recycled seawater medium, make this microalga an excellent candidate for large-scale outdoor cultivation for biodiesel production.