Identification of Burkholderia cepacia strains that express a Burkholderia pseudomallei-like capsular polysaccharide.

Burkholderia pseudomallei and Burkholderia cepacia are Gram-negative, soil-dwelling bacteria that are found in a wide variety of environmental niches. While B. pseudomallei is the causative agent of melioidosis in humans and animals, members of the B. cepacia complex typically only cause disease in immunocompromised hosts. In this study, we report the identification of B. cepacia strains isolated from either patients or soil in Laos and Thailand that express a B. pseudomallei-like 6-deoxyheptan capsular polysaccharide (CPS). These B. cepacia strains were initially identified based on their positive reactivity in a latex agglutination assay that uses the CPS-specific monoclonal antibody (mAb) 4B11. Mass spectrometry and recA sequencing confirmed the identity of these isolates as B. cepacia (formerly genomovar I). Total carbohydrates extracted from B. cepacia cell pellets reacted with B. pseudomallei CPS-specific mAbs MCA147, 3C5, and 4C4, but did not react with the B. pseudomallei lipopolysaccharide-specific mAb Pp-PS-W. Whole genome sequencing of the B. cepacia isolates revealed the presence of genes demonstrating significant homology to those comprising the B. pseudomallei CPS biosynthetic gene cluster. Collectively, our results provide compelling evidence that B. cepacia strains expressing the same CPS as B. pseudomallei co-exist in the environment alongside B. pseudomallei. Since CPS is a target that is often used for presumptive identification of B. pseudomallei, it is possible that the occurrence of these unique B. cepacia strains may complicate the diagnosis of melioidosis.IMPORTANCEBurkholderia pseudomallei, the etiologic agent of melioidosis, is an important cause of morbidity and mortality in tropical and subtropical regions worldwide. The 6-deoxyheptan capsular polysaccharide (CPS) expressed by this bacterial pathogen is a promising target antigen that is useful for rapidly diagnosing melioidosis. Using assays incorporating CPS-specific monoclonal antibodies, we identified both clinical and environmental isolates of Burkholderia cepacia that express the same CPS antigen as B. pseudomallei. Because of this, it is important that staff working in melioidosis-endemic areas are aware that these strains co-exist in the same niches as B. pseudomallei and do not solely rely on CPS-based assays such as latex-agglutination, AMD Plus Rapid Tests, or immunofluorescence tests for the definitive identification of B. pseudomallei isolates.

Outbreak investigation of NDM-producing Burkholderia cepacia causing neonatal sepsis in Pakistan.

Aim: To investigate the outbreak of Burkholderia cepacia complex (BCC), mortality, antimicrobial resistance and associated risk factors in the neonatal intensive care unit. Method: Eighteen blood culture samples from neonates and twenty swab samples from different neonatal intensive care unit surfaces were collected. The VITEK 2 was used to confirm the isolates and generate the antibiogram. PCR was used to identify blaNDM. Results: Eighteen samples tested positive for BCC, and 10/18 (55.5%) of the neonates died. 13/18 (72%) of the neonates had late-onset neonatal sepsis, and 10/18 (55%) had low birth weight. Resistance to minocycline and chloramphenicol was 100%, 72.2% to meropenem; 72.2% NDM gene was found in neonates and was 20% from the environment. Conclusion: Outbreak of NDM-producing BCC resulting in high neonatal mortality in NICU.

Neonatal septicemia, or blood poisoning, is a dangerous illness in newborns. It is caused by bacteria or other infections entering the blood and spreading. Pregnancy, labor, delivery and exposure after birth can result in infection of the newborn. Neonatal septicemia kills 700,000 babies worldwide, mostly in low- and middle-income countries. Burkholderia cepacia complex bacteria can cause infections in people with weaker immune systems or other disorders. They are particularly dangerous in hospitals, as they can cause chronic lung problems. This study collected blood samples from newborns with blood poisoning. Most samples that contained Burkholderia cepacia complex were not susceptible to drugs. Four of the newborns carried the same bacteria, indicating that hospital staff should practice hand washing and equipment and environmental cleaning to prevent the spread of the bacteria.

Burkholderia vietnamiensis causing infections in noncystic fibrosis patients in a tertiary care hospital in Mexico.

Burkholderia cepacia complex (Bcc) species are opportunistic pathogens widely distributed in the environment and often infect people with cystic fibrosis (CF). This study aims to determine which genomovars of the Bcc can cause infections in non-CF patients from a tertiary care hospital in Mexico and if they carry virulence factors that could increase their pathogenicity. We identified 23 clinical isolates that carry the recA gene. Twenty-two of them belongs to the genomovar V (B. vietnamiensis) and one to the genomovar II (B. multivorans). Thirteen pulsotypes were identified among 22 B. vietnamiensis isolates. All clinical isolates produced biofilm were motile and cytotoxic on murine macrophage-like RAW264.7 and in A549 human lung epithelial cells. In conclusion, B. vietnamiensis causes infections in non-CF patients in a tertiary care hospital in Mexico, rapid identification of this pathogen can help physicians to establish a better antimicrobial treatment.

Molecular Research Comparing the Probabilities of Burkholderia Cepacia Bacterium Diagnosis Procedures.

Burkholderia cepacia is found as part of the B. cepacia complex (Bcc), a collection of highly pathogenic organisms. The Bcc is present almost everywhere in nature; however, it is most prevalent in damp settings, plant roots, and soils. Moreover, Bcc is a major source of morbidity and death in patients due to its high intrinsic antibiotic resistance. The present study aims to isolate and identify gram-negative aerobic bacteria from clinical samples derived from a variety of pathological diseases and investigate the bacterium's virulence factors and genes. The current study included 250 specimens collected from patients suffering from diabetic foot ulcers, urine, burn, wound, sputum, and discharge from the eyes. The samples were collected from both sexes with the age range of 1-75 years. The recorded data showed that males had a higher frequency of infection (79.2%) than females (52%). The results revealed that 7.6% of infected females were between 1-15 years old, while 22% of infected males were aged between 31-45 years. In addition, 26.8% of infected patients (both males and females) were aged between 31-45 years.

Diagnostic Uncertainty, Microbes, and the Isolation of People with Cystic Fibrosis.

The framing of cystic fibrosis (CF) changed from a strictly genetic disease in the mid- to late-twentieth century to a genetic/infectious hybrid of sorts by the early twenty-first century, providing an opportunity to examine the nature of disease definition in medicine. Respiratory infections had long been associated with CF, yet it was not until the late twentieth century that many physicians became concerned about the possibility of patient-to-patient transmission of a particularly pathogenic microorganism. Initially termed Pseudomonas cepacia, the microbe was linked to rapid decline and even death in some people with CF, and early efforts to prevent its spread included the segregation of infected individuals. However, soon after segregation was implemented in a range of medical and social contexts, physicians began to suspect that people with CF did not always test positive for P. cepacia in the setting of infection, due to challenges isolating and identifying the microorganism in the laboratory. These sources of diagnostic uncertainty, coupled with the severe health outcomes associated with P. cepacia infection, prompted those in leadership positions to treat all people with CF as a potential source of contagion and restrict their in-person interactions, a practice that has had a profound impact on the CF community.

Enhancement of protein thermostability by three consecutive mutations using loop-walking method and machine learning.

We developed a method to improve protein thermostability, "loop-walking method". Three consecutive positions in 12 loops of Burkholderia cepacia lipase were subjected to random mutagenesis to make 12 libraries. Screening allowed us to identify L7 as a hot-spot loop having an impact on thermostability, and the P233G/L234E/V235M mutant was found from 214 variants in the L7 library. Although a more excellent mutant might be discovered by screening all the 8000 P233X/L234X/V235X mutants, it was difficult to assay all of them. We therefore employed machine learning. Using thermostability data of the 214 mutants, a computational discrimination model was constructed to predict thermostability potentials. Among 7786 combinations ranked in silico, 20 promising candidates were selected and assayed. The P233D/L234P/V235S mutant retained 66% activity after heat treatment at 60 °C for 30 min, which was higher than those of the wild-type enzyme (5%) and the P233G/L234E/V235M mutant (35%).

Co-Expression of a Thermally Stable and Methanol-Resistant Lipase and Its Chaperone from Burkholderia cepacia G63 in Escherichia coli.

Biodiesel biosynthesis with enzymatic transesterification is considered green, sustainable, and environmentally friendly method. Lipase from Burkholderia cepacia G63 has excellent catalytic properties in biodiesel production. Lipase chaperones promote secretion and folding of enzymes, thereby enhancing enzymatic activity. In the current study, heterologous co-expression of lipase (lipA) and chaperone (lipB) was achieved in Escherichia coli through codon optimization. The enzymatic activity of purified and renatured lipAB was 2080.23 ± 19.18 U/g at 50 °C and pH 8.0. Moreover, lipAB showed increased resistance to pH and temperature changes, and lipAB retained stable catalytic properties after treatment with metal ions, organic solvents, and surfactants, namely Mg2+, methanol, and Triton-100X. Besides, using recombinant lipase lipAB as catalysts, biodiesel was synthesized using rapeseed oil under 50 °C for 72 h with a yield of 90.23%. Thus, the current study confirmed that co-expression of lipase and its chaperone is an effective strategy to enhance enzyme activity and improve the biochemical profile, meanwhile, showing that lipAB is a promising biocatalyst for biodiesel production.

Outbreak of Stenotrophomonas maltophilia and Burkholderia cepacia Bloodstream Infections at a Hemodialysis Center.

Patients undergoing hemodialysis are at an increased risk for bloodstream infections (BSIs). Infection usually occurs because of contamination of water supply, water treatment, distribution systems, or reprocessing dialyzers. Here, we report an outbreak of BSIs caused by Stenotrophomonas maltophilia (n = 21) and Burkholderia cepacia (n = 22) among dialyzed patients at a large hemodialysis center in Brazil. Overall, three patients died (7%), two of which had bacteremia caused by S. maltophilia and the other had a B. cepacia infection. We collected water samples from different points of the hemodialysis system for culture and typing. Genetic patterns were identified through polymerase chain reaction-random amplified polymorphic DNA (PCR-RAPD) and pulsed-field gel electrophoresis. The same genotypes of S. maltophilia and B. cepacia recovered from blood cultures were found in dialysis water. Also, multiple genetic profiles were identified among water isolates, suggesting heavy contamination. Bacteremia cases persisted even after implementing standard control measures, which led us to believe that the piping system was contaminated with microbial biofilms. Soon after we changed the entire plumbing system, reported cases dropped back to the number typically expected, and the outbreak came to an end.

Cloning, expression and characterization of catechol 1,2-dioxygenase from Burkholderia cepacia.

The present study reports on the cloning, expression and characterization of catechol 1,2-dioxygenase (CAT) of bacterial strains isolated from dioxin-contaminated soils in Vietnam. Two isolated bacterial strains DF2 and DF4 were identified as Burkholderia cepacia based on their 16S rRNA sequences. Their genes coding CAT was amplified with a specific pair of primers. Recombinant CAT (rCAT) was expressed in E. coli M15 cells and its activity was confirmed by the detection of cis,cis-muconic acid, a product from catechol, by high-performance liquid chromatography (HPLC) analysis. The rCAT of DF4 had an optimal pH and temperature of 7 and 30°C, respectively. Metal ions, such as Zn2+ and Mn2+, and surfactants, such as SDS, Tween 20 and Triton X100, strongly inhibited enzyme activity, while K+ slightly increased the activity.

Epidemiological investigation and successful management of a Burkholderia cepacia outbreak in a neurotrauma intensive care unit.

OBJECTIVE: The detailed epidemiological and molecular characterization of an outbreak of Burkholderia cepacia at a neurotrauma intensive care unit of a level 1 trauma centre is described. The stringent infection control interventions taken to successfully curb this outbreak are emphasized. METHODS: The clinical and microbiological data for those patients who had more than one blood culture that grew B. cepacia were reviewed. Bacterial identification and antimicrobial susceptibility testing was done using automated Vitek 2 systems. Prospective surveillance, environmental sampling, and multilocus sequence typing (MLST) were performed for extensive source tracking. Intensive infection control measures were taken to further control the hospital spread. RESULTS: Out of a total 48 patients with B. cepacia bacteraemia, 15 (31%) had central line-associated blood stream infections. Two hundred and thirty-one environmental samples were collected and screened, and only two water samples grew B. cepacia with similar phenotypic characteristics. The clinical strains characterized by MLST typing were clonal. However, isolates from the water represented a novel strain type (ST-1289). Intensive terminal cleaning, disinfection of the water supply, and the augmentation of infection control activities were done to curb the outbreak. A subsequent reduction in bacteraemia cases was observed. CONCLUSION: Early diagnosis and appropriate therapy, along with the rigorous implementation of essential hospital infection control practices is required for successful containment of this pathogen and to curb such an outbreak.

Transcriptional analysis of the laccase-like gene from Burkholderia cepacia BNS and expression in Escherichia coli.

Bacterial laccases have received considerable attention because of several advantages associated with the higher environmental stability of these enzymes compared with fungal laccases. In this study, a laccase-like gene from Burkholderia cepacia BNS was successfully cloned. This gene was found to encode a mature protein of 279 amino acids that exhibited laccase activity in dimer form. The mature protein was found to contain approximately 4 mol of copper per monomer, and the metal ion-binding sites were predicted. BC_lacL gene transcription levels were analyzed by qRT-PCR to study expression patterns in the presence of different putative inducers (copper ions, guaiacol, veratryl alcohol, vanillin, coniferaldehyde, p-coumaric acid, sinapic acid, and ferulic acid). Copper ions had a positive effect on both transcription levels and intracellular laccase activity. Interestingly, upon induction with sinapic acid, BC_lacL gene transcription was lower than in the presence of copper ions, but laccase activity was highest under these conditions. The BC_lacL protein expressed in Escherichia coli exhibited a specific activity of 7.81 U/mg with 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as the substrate and 12.3 U/mg with 2,6-dimethoxyphenol (2,6-DMP) as the substrate after purification through Ni-affinity chromatography. The optimal activity and kinetic parameters of the recombinant BC_lacL protein were observed (kcat/Km = 3.96 s-1 µM-1) at a pH of 4.0 at 55 °C for ABTS oxidization and (kcat/Km = 11.6 s-1 µM-1) at a pH of 10.0 at 75 °C for 2,6-DMP oxidization. The protein exhibited high stability in an alkaline environment, with a half-life of more than 12 h. The same results were obtained via decolorization of eight dyes. Hence, this laccase-like enzyme may have potential industrial applications.

Evolving metabolism of 2,4-dinitrotoluene triggers SOS-independent diversification of host cells.

The molecular mechanisms behind the mutagenic effect of reactive oxygen species (ROS) released by defective metabolization of xenobiotic 2,4-dinitrotoluene (DNT) by a still-evolving degradation pathway were studied. To this end, the genes required for biodegradation of DNT from Burkholderia cepacia R34 were implanted in Escherichia coli and the effect of catabolizing the nitroaromatic compound monitored with stress-related markers and reporters. Such a proxy of the naturally-occurring scenario faithfully recreated the known accumulation of ROS caused by faulty metabolism of DNT and the ensuing onset of an intense mutagenesis regime. While ROS triggered an oxidative stress response, neither homologous recombination was stimulated nor the recA promoter activity increased during DNT catabolism. Analysis of single-nucleotide changes occurring in rpoB during DNT degradation suggested a relaxation of DNA replication fidelity rather than direct damage to DNA. Mutants frequencies were determined in strains defective in either converting DNA damage into mutagenesis or mediating inhibition of mismatch repair through a general stress response. The results revealed that the mutagenic effect of ROS was largely SOS-independent and stemmed instead from stress-induced changes of rpoS functionality. Evolution of novel metabolic properties thus resembles the way sublethal antibiotic concentrations stimulate the appearance of novel resistance genes.

Prevalencia de especies del complejo Burkholderia cepacia en pacientes con fibrosis quística en Argentina durante el período 2011-2015 / Prevalence of Burkholderia cepacia complex species in cystic fibrosis patients in Argentina during the period 2011-2015

Introducción: En la actualidad el complejo Burkholderia cepacia (B. cepacia) está compuesto por 20 especies filogenéticamente muy relacionadas. Algunas especies han emergido como patógenos oportunistas en pacientes inmunocomprometidos y son responsables de brotes intrahospitalarios. El complejo B. cepacia es un reconocido patógeno respiratorio en pacientes con fibrosis quística. B. cenocepacia y Burkholderia multivorans (B. multivorans) son las especies prevalentes en el mundo, según la literatura. Sin embargo, grupos de investigación en Argentina han descripto una epidemiología local particular, con prevalencia de la especie Burkholderia contaminans (B. contaminans). Métodos: Se estudiaron 68 aislamientos del complejo B. cepacia aislados de 46 pacientes con fibrosis quística de 14 hospitales distribuidos en 9 provincias del país. La identificación se llevó a cabo por métodos fenotípicos convencionales y fue confirmada por secuenciación parcial del gen recA. Los alineamientos de las secuencias se realizaron mediante el programa BLAST y fueron comparadas con las secuencias de las cepas tipo de cada una de las especies del complejo B. cepacia. Se determinó el perfil de sensibilidad a 4 agentes antimicrobianos para los aislamientos de las especies más prevalentes, según lo recomendado por la norma CLSI M45. Resultados: La especie prevalente resultó B. contaminans (49%, n = 33) seguida por B. cenocepacia (25%; n = 17). El resto de las especies identificadas fueron: Burkholderia seminalis (B. seminalis) (7%; n = 5), B. cepacia (7%; n = 5), B. multivorans (6%; n = 4), Burkholderia vietnamensis (5%, n = 3) y Burkholderia pyrrocinia (1%; n = 1). El 46% de los aislamientos de B. contaminans fueron resistentes a SXT y el 76% sensible a MIN, MEM y CAZ. Los aislamientos de B. cenocepacia fueron 100% resistentes a SXT y MIN, y el 47% a CAZ y MEM. En B. seminalis se observa un alto nivel de resistencia a TMS (80%), CAZ (60%) y MIN (60%), y un 60% de los aislamientos mostraron sensibilidad intermedia a MEM. Conclusión: Los únicos países que han documentado la prevalencia de B. contaminans en infecciones respiratorias de pacientes fibroquísticos por complejo B. cepacia son Argentina, España y Portugal, y recientemente se reportó un caso de 2 pacientes con fibrosis quística en Irlanda. Debido a la alta frecuencia con que B. contaminans es aislada en nuestro país, es necesario promover la investigación de las posibles fuentes de infección y comprender los factores y mecanismos implicados en la aparente mayor transmisibilidad de esta especie. Se observaron distintos patrones de sensibilidad entre las especies estudiadas

Introduction: Burkholderia cepacia (B. cepacia) complex is composed of 20 phylogenetically closely related bacterial species. Some species have emerged as opportunistic pathogens in immunocompromised patients and are responsible for nosocomial outbreaks. The B. cepacia complex is a recognized respiratory pathogen in patients with cystic fibrosis. Burkholderia cenocepacia and Burkholderia multivorans (B. multivorans) are the most prevalent species in the world, according to the literature. However, research groups in Argentina have described a particular local epidemiology, with prevalence of Burkholderia contaminans (B. contaminans). Methods: A total of 68 isolates of B. cepacia complex recovered of 46 cystic fibrosis patients attended at 14 hospitals distributed in 9 provinces of the country were studied. Identification was carried out by conventional phenotypic methods and was confirmed by recA gene sequencing. Sequences were analysed using the BLASTN program and comparing with B. cepacia complex type strains sequences deposited in GenBank. Antibiotic susceptibility tests were performed on isolates of the most prevalent species according to CLSI M45 guidelines. Results: The prevalent specie was B. contaminans (49%, n = 33) followed by B. cenocepacia (25%; n = 17). The remaining species were Burkholderia seminalis (B. seminalis) (7%, n = 5), B. cepacia (7%, n = 5), B. multivorans (6%, n = 4), Burkholderia vietnamensis (5%, n=3) and Burkholderia pyrrocinia (1%; n = 1). The 46% of B. contaminans isolates were resistant to SXT and 76% sensitive to MIN, MEM and CAZ. The isolates of B. cenocepacia were 100% resistant to SXT and MIN and 47% to CAZ and MEM. B. seminalis showed high levels of resistance to TMS (80%), CAZ (60%) and MIN (60%), and 60% of the isolates showed intermediate sensitivity to MEM. Conclusion: Previous reports have described the prevalence of B. contaminans isolation from cystic fibrosis patients in Argentina, Spain and Portugal, and a case of two patients with cystic fibrosis in Ireland has recently been reported. Due to the high frequency with which B. contaminans is isolated in our country, it is necessary to promote the investigation of possible sources of infection and to understand the factors and mechanisms involved in the apparent greater transmissibility of this species. Different antimicrobial resistance profiles were detected between the species

Evaluating the use of whole-genome sequencing for outbreak investigations in the lack of closely related reference genome.

Whole-genome sequencing (WGS) has emerged as a powerful molecular typing method for outbreak analysis enabling the rapid discrimination between outbreak and non-outbreak isolates. However, such analysis can be challenging in the absence of closely related reference genomes. In this study, we assessed the use of WGS in investigating an outbreak of a relatively understudied bacterial pathogen with no publicly available closely related reference genome. Eleven Burkholderia cepacia complex (Bcc) isolates (seven from patients and four from disposable dermal gloves packages) that were collected during an outbreak were sequenced using the Illumina MiSeq platform. Our results showed that mapping the 11 sequenced Bcc outbreak isolates against a genetically distant reference genome yield loses coverage (31.6-48.3%) and a high number of detected false single-nucleotide polymorphisms (SNPs) (1123-2139). Therefore, a reference genome consensus from an outbreak clinical isolate was generated by combining both de novo assembly and mapping approaches. Based on this approach, we were able to demonstrate that the Bcc outbreak isolates were closely related and were phylogenetically distinct from the 11 publically available Bcc genomes. In addition, the pairwise SNP distance analysis detected only 1 to 6 SNPs differences among the outbreak isolates, confirming that contaminated disposable dermal gloves were the cause of the outbreak.

Outbreak of Burkholderia cepacia bacteraemia in a tertiary care centre due to contaminated ultrasound probe gel.

BACKGROUND: Burkholderia cepacia is an important opportunistic organism in hospitalized and immunocompromised patients, particularly in cystic fibrosis. AIMS: To describe the epidemiological investigation of an outbreak of B. cepacia bacteraemia. METHODS: The study examined 14 patients during their admission to three intensive care units in a tertiary care hospital between January and June 2016. The outbreak involved nine (57%) female and six (43%) male patients. All patients were adults of ages ranging from 19 to 85 years with a median age of 52 years. Patients' medical charts, laboratory cultures, exposures, and central line insertion procedures were reviewed. FINDINGS: B. cepacia was isolated from the blood cultures of 14 patients resulting from contamination of the gel applied to the ultrasound probe used to guide the insertion of a central venous catheter. Molecular pathogen typing using pulsed-field gel electrophoresis showed 95% similarity between the B. cepacia isolates from the blood of these patients and those isolated from the ultrasound gel. CONCLUSION: Ongoing surveillance and prompt investigation of unusual disease outbreaks are vital for identifying sources of contamination of B. cepacia and protecting at-risk patients. Sound epidemiological methods are very important for identifying the source of any hospital infection outbreak.

Outbreak of Burkholderia cepacia pseudobacteraemia caused by intrinsically contaminated commercial 0.5% chlorhexidine solution in neonatal intensive care units.

BACKGROUND: Burkholderia cepacia is intrinsically resistant to certain antiseptics. The authors noted a sudden increase in the frequency of isolation of B. cepacia from blood cultures in a neonatal intensive care unit (NICU) of a university-affiliated hospital. AIM: To identify the source and intervene in the ongoing infections. METHODS: The cases were defined as patients with positive blood cultures for B. cepacia in an NICU between November 2014 and January 2015. Medical records were reviewed and NICU healthcare workers were interviewed. Samples of suspected antiseptics, blood culture bottles, cotton balls, gauze and a needle used in the NICU were analysed microbiologically. FINDINGS: During the outbreak period, B. cepacia was identified in 25 blood cultures obtained from 21 patients. The clinical features of the patients were suggestive of pseudobacteraemia. Regarding environmental samples, B. cepacia was cultured from 0.5% chlorhexidine gluconate (CHG) solution products that had been used as a skin antiseptic during blood drawing in the NICU. The clinical B. cepacia isolate and two strains obtained from 0.5% CHG exhibited identical pulsed-field gel electrophoresis patterns. After the CHG products were withdrawn, the outbreak was resolved. CONCLUSIONS: The pseudobacteraemia cases were caused by contaminated 0.5% CHG produced by a single manufacturer. Stricter government regulation is needed to prevent contamination of disinfectants during manufacturing. In addition, microbial contamination of antiseptics and disinfectants should be suspected when a B. cepacia outbreak occurs in hospitalized patients.

Metabolism-mediated induction of zinc tolerance in Brassica rapa by Burkholderia cepacia CS2-1.

Brassica rapa (Chinese cabbage) is an essential component of traditional Korean food. However, the crop is often subject to zinc (Zn+) toxicity from contaminated irrigation water, which, as a result, compromises plant growth and production, as well as the health of human consumers. The present study investigated the bioaccumulation of Zn+ by Burkholderia cepacia CS2-1 and its effect on the heavy metal tolerance of Chinese cabbage. Strain CS2-1 was identified and characterized on the basis of 16S rRNA sequences and phylogenetic analysis. The strain actively produced indole-3-acetic acid (3.08 ± 0.21 µg/ml) and was also able to produce siderophore, solubilize minerals, and tolerate various concentrations of Zn+. The heavy metal tolerance of B. rapa plants was enhanced by CS2-1 inoculation, as indicated by growth attributes, Zn+ uptake, amino acid synthesis, antioxidant levels, and endogenous hormone (ABA and SA) synthesis. Without inoculation, the application of Zn+ negatively affected the growth and physiology of B. rapa plants. However, CS2-1 inoculation improved plant growth, lowered Zn+ uptake, altered both amino acid regulation and levels of flavonoids and phenolics, and significantly decreased levels of superoxide dismutase, endogenous abscisic acid, and salicylic acid. These findings indicate that B. cepacia CS2-1 is suitable for bioremediation against Zn+-induced oxidative stress.

Analysis of ParB-centromere interactions by multiplex SPR imaging reveals specific patterns for binding ParB in six centromeres of Burkholderiales chromosomes and plasmids.

Bacterial centromeres-also called parS, are cis-acting DNA sequences which, together with the proteins ParA and ParB, are involved in the segregation of chromosomes and plasmids. The specific binding of ParB to parS nucleates the assembly of a large ParB/DNA complex from which ParA-the motor protein, segregates the sister replicons. Closely related families of partition systems, called Bsr, were identified on the chromosomes and large plasmids of the multi-chromosomal bacterium Burkholderia cenocepacia and other species from the order Burkholeriales. The centromeres of the Bsr partition families are 16 bp palindromes, displaying similar base compositions, notably a central CG dinucleotide. Despite centromeres bind the cognate ParB with a narrow specificity, weak ParB-parS non cognate interactions were nevertheless detected between few Bsr partition systems of replicons not belonging to the same genome. These observations suggested that Bsr partition systems could have a common ancestry but that evolution mostly erased the possibilities of cross-reactions between them, in particular to prevent replicon incompatibility. To detect novel similarities between Bsr partition systems, we have analyzed the binding of six Bsr parS sequences and a wide collection of modified derivatives, to their cognate ParB. The study was carried out by Surface Plasmon Resonance imaging (SPRi) mulitplex analysis enabling a systematic survey of each nucleotide position within the centromere. We found that in each parS some positions could be changed while maintaining binding to ParB. Each centromere displays its own pattern of changes, but some positions are shared more or less widely. In addition from these changes we could speculate evolutionary links between these centromeres.

Contribution of native phosphorous-solubilizing bacteria of acid soils on phosphorous acquisition in peanut (Arachis hypogaea L.).

The present investigation analyzes the in vitro P solubilization [Ca-P, Al-P, Fe(II)-P, and Fe(III)-P] efficiency of native PSB strains from acid soils of Odisha and exploitation of the same through biofertilization in peanut (Arachis hypogaea L.) growth and P acquisition. One hundred six numbers of soil samples with pH ≤ 5.50 were collected from five districts of Odisha viz., Balasore, Cuttack, Khordha, Keonjhar, and Mayurbhanj. One bacterial isolate from each district were selected and analyzed for their P solubilization efficiency in National Botanical Research Institute Phosphate broths with Ca, Al, and Fe-complexed phosphates. CTC12 and KHD08 transformed more amount of soluble P from Ca-P (CTC12 393.30 mg/L; KHD08 465.25 mg/L), Al-P (CTC12 40.00 mg/L; KHD08 34.50 mg/L), Fe(III)-P (CTC12 175.50 mg/L; KHD08 168.75 mg/L), and Fe(II)-P (CTC12 47.40 mg/L; KHD08 42.00 mg/L) after 8 days of incubation. The bioconversion of P by all the five strains in the broth medium followed the order Ca-P > Fe(III)-P > Fe(II)-P > Al-P. The identified five strains were Bacillus cereus BLS18 (KT582541), Bacillus amyloliquefaciens CTC12 (KT633845), Burkholderia cepacia KHD08 (KT717633), B. cepacia KJR03 (KT717634), and B. cepacia K1 (KM030037) and further studied for biofertilization effects on peanut. CTC12 and KHD08 enhanced the soil available P around 65 and 58% and reduced the amount of each Al3+ about 79 and 81%, respectively, over the uninoculated control pots in the peanut rhizosphere. Moreover, all tested PSB strains could be able to successfully mobilize P from inorganic P fractions (non-occluded Al-P and Fe-P). The strains CTC12 and KHD08 increased the pod yield (114 and 113%), shoot P (92 and 94%), and kernel P (100 and 101%), respectively, over the control. However, B. amyloliquefaciens CTC12 and B. cepacia KHD08 proved to be the potent P solubilizers in promoting peanut growth and yield.