Comparative genomics reveals diverse capsular polysaccharide synthesis gene clusters in emerging Raoultella planticola

Raoultella planticola is an emerging zoonotic pathogen that is associated with rare but life-threatening cases of bacteremia, biliary tract infections, and urinary tract infections. Moreover, increasing antimicrobial resistance in the organism poses a potential threat to public health. In spite of its importance as a human pathogen, the genome of R. planticola remains largely unexplored and little is known about its virulence factors. Although lipopolysaccharides has been detected in R. planticola and implicated in the virulence in earlier studies, the genetic background is unknown. Here, we report the complete genome and comparative analysis of the multidrug-resistant clinical isolate R. planticola GODA. The complete genome sequence of R. planticola GODA was sequenced using single-molecule real-time DNA sequencing. Comparative genomic analysis reveals distinct capsular polysaccharide synthesis gene clusters in R. planticola GODA. In addition, we found bla TEM-57 and multiple transporters related to multidrug resistance. The availability of genomic data in open databases of this emerging zoonotic pathogen, in tandem with our comparative study, provides better understanding of R. planticola and the basis for future work.

Yield and rheological properties of exopolysaccharide from a local isolate: Xanthomonas axonopodis pv. vesicatoria

Background: The aim of the present study was to evaluate gum productivity of a local strain, Xanthomonas axonopodis pv. vesicatoria, isolated from pepper plant, and its rheological behavior for the first time compared to the standard strain, Xanthomonas campestris DSM 19000 (NRRL B-1459). The influence of operational conditions (agitation rate and inoculum volume) on gum production and rheological properties of gums from the Xanthomonas strains were investigated. Results: The isolated strain of Xanthomonas showed similar xanthan yield compared to the standard strain. Furthermore, this study clearly confirmed that gum yield depended on bacterial strain, agitation rate, and inoculum size. The most suitable conditions for the gum production in an orbital shaker in terms of agitation rate and inoculum size were 180 rpm and 5%, respectively, resulting in an average production of 10.96 and 11.19 g/L for X. axonopodis pv.vesicatoria and X. campestris DSM 19000, respectively. Regarding the rheological properties, Ostwald-de-Waele and power law models were used to describe flow and oscillatory behavior of the gum solutions, respectively. Consistency of the novel gum solution remarkably was much higher than the commercial xanthan gum solution. Flow and oscillatory behavior and their temperature ramps showed that weak gel-like structure could be obtained with less gum concentrations when the novel gum was used. Conclusion: Therefore, yield and technological properties of the aqueous solutions of the exopolysaccharide synthesized by X. axonopodis pv. vesicatoria were observed to be more suitable for industrial production.

Selection of superior bifidobacteria in the presence of rotavirus

The main purpose of this study was to investigate bifidobacteria flora in fecal samples from children with rotavirus infection and determine the significance of their selected probiotic properties for improvement of health status. Enzyme-linked immunosorbent assay was used to identify rotavirus antigen in fecal samples from 94 patients with gastroenteritis and from 30 without gastroenteritis. Bifidobacteria were identified by selective media, gram reaction, colony morphology, fructose-6-phosphate phosphoketolase enzyme activity and classical identification tests. Exopolysaccharide (EPS) production was identified by phenol-sulphuric acid method. The modified method was then used to identify the quantity of taurocholic and glycocholic acid deconjugation and cholesterol elimination of the strains. Thirty-five of the 94 fecal samples were found positive for rotavirus antigen (37.23%). Bifidobacteria were identified in 59 of the samples. The EPS production ranges were 29.56-102.21 mg/L. The cholesterol elimination rates ranged between 8.36-39.22%. Furthermore, a positive and strong correlation was determined between EPS production and the presence of cholesterol (r=0.984, P<0.001). The deconjugation rates for the sodium glycocholate group was higher than the sodium taurocholate group. Rotavirus (+) bifidobacteria strains had higher EPS production, deconjugation rate and cholesterol elimination compared to bifidobacteria strains isolated from children in the rotavirus (-) sample and without gastroenteritis. Significant differences were observed among groups in all parameters (P<0.05). Given the increased number of rotavirus cases in Turkey and worldwide, it is very important to add superior bifidobacteria in the diets of infected children to improve the intestinal and vital functions.

Plant Growth Promotion and Root Colonization by EPS Producing Enterobacter sp. RZS5 under Heavy Metal Contaminated Soil.

The heavy metal resistant bacterium isolated from field soil and identified as Enterobacter sp. RZS5 tolerates a high concentration (100-2000 mM) of various heavy metal ions such as Mn2+, Ni2+, Zn2+, Cu2+, CO2+ and Fe2+ when grown in such environment and produces exopolysaccharides (EPS). Here, we have demonstrated EPS production by Enterobacter sp. RZS5 during 60 h of growth in yeast extract mannitol broth (YEMB). The yield increased by two fold after the addition of 60 M of Ca2+; 50 M of Fe2+ and 60 M of Mg2+ ions in YEMB, and the optimization of physico-chemical parameters. EPS was extracted with 30% (v/v) of isopropanol as against the commonly used 50% (v/v) isopropanol method. EPS-rich broth promoted seed germination, shoot height, root length, number of leaves and chlorophyll content of wheat (Triticum aestivum) and peanut (Arachis hypogaea) seeds. The higher colony-forming unit of Enterobacter sp. in soil inoculated with EPS rich broth of Enterobacter sp. indicated the root colonizing potential and rhizosphere competence of the isolate. The FTIR spectra of the EPS extract confirmed the presence of the functional group characteristics of EPS known to exhibit a high binding affinity towards certain metal ions. This overall growth and vigour in plants along with the effective root colonization, reflected the potential of the isolate as an efficient bio-inoculant in bioremediation.

Optimization of surfactin production by Bacillus subtilis ATCC 6633 in a miniaturized bioreactor

In recent years, biosurfactants due to wide applications in chemical, petroleum, food and pharmaceutical industries, have been widely considered by researchers. Biosurfactants are produced by a series of microorganisms, so it is important to screen culture medium and operating conditions in miniaturized bioreactors prior to scaling up to large bioreactors.In this study, using a kind of miniaturized bioreactor called ventilation flask, optimal production conditions, including filling volume and shaking frequency to produce a surfactin-type biosurfactant by Bacillus subtilis ATCC 6633, were examined. Moreover, the effect of oxygen transfer rate [OTR] on the surfactin production was investigated according to Amoabediny and Buchs model. The results indicated that the maximum biomass and biosurfactant yield which obtained under optimal conditions [filling volume of 15 mL and shaking frequency of 300 rpm] were evaluated 0.3 g/L/h and 0.0485 g/L/h, respectively. Also, at the same conditions, the amount of surface tension decreased from 60.5 mN/m to 31.7 mN/m and the maximum oxygen transfer rate [OTR[max]] obtained as 0.01 mol/L/h

Influence of agitation and aeration in xanthan production by Xanthomonas campestris pv pruni strain 101 / Influencia de la agitación y la aireación en la producción de xantano por Xanthomonas campestris pv. pruni cepa 101

Production, viscosity, and chemical composition of xanthan synthesized by bacterium Xanthomonas campestris pv pruni strain 101 were evaluated in bioreactor systems. During the process, the volumetric oxygen mass transfer coefficient (kLa) and the biomass were determined and the pH was monitored. The cultures were grown in a 3 l bioreactor, with aeration and agitation varying as follows: conditions (A) 300 rpm, 3 vvm and (B) 200 rpm, 2 vvm, at 28 °C. Our results showed that gum production was dependent on kLa, with a maximum yield of 8.15 g/l at 300 rpm, 3 vvm, 54 h of fermentation, kLa 21.4/h, while biomass was not affected. All aqueous solutions of 3% (w/v) xanthans synthesized showed a pseudoplastic behavior. The highest viscosity was reached under the strongest aeration/agitation conditions. All xanthan samples contained glucose, mannose, rhamnose, and glucuronic acid as their main components. The highest agitation and aeration rates used under condition A (300 rpm and 3 vvm) favorably influenced the yield and viscosity of the xanthan produced by bacterium X. campestris pv pruni 101 at different fermentation times.

Se evaluó la producción, viscosidad y composición química del xantano sintetizado por la bacteria Xanthomonas campestris pv. pruni cepa 101 en un fermentador. Durante el proceso se controló el pH y se determinaron el coeficiente de transferencia de masa de oxígeno (kLa) y la producción de masa celular seca. Los cultivos se realizaron en un fermentador de 3 l variando la aireación y la agitación, en las siguientes condiciones: (A) 300 rpm, 3 vvm y (B) 200 rpm, 2 vvm; a 28 °C. Nuestros resultados mostraron que la producción de goma fue dependiente del kLa, con un rendimiento máximo de 8,15 g/l a 300 rpm y 3 vvm a las 54 h de fermentación, kLa de 21,4/h, mientras que la producción de biomasa no se afectó. Todas las soluciones acuosas de xantano al 3% (m/v) sintetizadas presentaron comportamiento pseudoplástico. La mayor viscosidad se alcanzó en la condición de aireación/agitación más intensa. Todas las muestras de xantano contenían glucosa, manosa, ramnosa y ácido glucurónico como constituyentes principales. La mayor tasa de agitación y aireación utilizada en la condición A (300 rpm y 3 vvm) influyó favorablemente en el rendimiento y la viscosidad del xantano producido por la bacteria X. campestris pv. pruni 101 a diferentes tiempos de fermentación.

Fermentation technologies for the production of exopolysaccharide-synthesizing Lactobacillus rhamnosus concentrated cultures

The exopolysaccharide (EPS)-producing cultures such as Lactobacillus rhamnosus RW-9595M present a challenge for the culture producers because the high viscosity of the fermented growth medium makes it difficult to recover the cells by centrifugation or filtration. This study examined four approaches to reduce viscosity of the medium while producing high cell densities: incubation temperature, extended incubation in the stationary growth phase, production in alginate gel beads and fed-batch fermentation technology. Automated spectrophotometry (AS) was used to study the effects of temperature, pH and lactate level on growth of the strain. In AS assays, there was no significant difference in final maximal biomass production at temperatures ranging between 34 ºC to 44 ºC, but lower yields were noted at 46 C. A pH below 6.0 and a lactate concentration higher than 4 percent almost completely prevented growth. Under batch fermentation conditions, the viscosity of the medium obtained at 37 C was two fold higher than for 44 ºC. For cultures produced at 37 ºC, centrifugation at 10000 g during 5 min did not allow complete recovery of cells, in contrast to cultures grown at 44 ºC. An extended period of incubation (5 hrs) in the stationary growth phase did not reduce the final viscosity of the growth medium. For similar biomass levels, the glucose-based fed-batch fermentation allowed a 40 percent reduction in viscosity of the fermented medium in comparison to traditional batch cultures. High-density cell populations (3 x 10(10) CFU/g) were obtained when L. rhamnosus RW-9595M was grown in alginate beads. However, overall biomass yields in the immobilized cell bioreactor were half of those obtained in free-cell fermentations. Therefore three methods of producing concentrated EPS-producing cultures are proposed.

Exopolissacarídeos bacterianos: produção e composição / Bacterial exopolysaccharides: production and composition

Os polissacarídeos de origem microbiana, chamados de biopolímeros ou gomas, apresentam muitas vantagens em relação aos hidrocolóides derivados de algas e plantas. Este trabalho discute a importância dos exopolissacarídeos bacterianos, sua síntese, produção e fatores que afetam esta mesma produção, bem como sua composição química.

A simple alternative method for rapid detection of slime produced by Staphylococcus epidermidis isolates in bacterial keratitis.

BACKGROUND & OBJECTIVES: Slime is a known virulence factor of Staphylococcus epidermidis. The conventional Christensen's method for detection of slime in the laboratory takes at least 48 h. We, therefore, tried to evaluate the efficacy of the Congo red agar method as a routine procedure for detecting slime among isolates from corneal ulcers. METHODS: A total of 244 isolates from corneal ulcers were identified as S. epidermidis by the standard procedures. Slime was detected both by the conventional Christensen's method as well as by the Congo red agar method. RESULTS: Ninety two (37.7%) isolates were positive and 86 (35.2%) were negative for slime by both the techniques. Fifty four (22.1%) isolates were positive in Congo red agar, but negative by Christensen's method; whereas only 12 (4.9%) were negative by Congo red but positive by Christensen's method. Detection of slime by Congo red agar method was rapid i.e., all the 146 strains were positive within 24 h of incubation. On the other hand, Christensen's method had a delayed response; 42.3 per cent (44/104) strains being negative during the first 24 h of incubation. INTERPRETATION & CONCLUSION: Our results suggested that culture on Congo red agar was a sensitive and rapid test for detecting slime. This might help in the quick identification in a routine laboratory of slime positive isolates in bacterial keratitis.

Extracellular polysaccharide production by Azorhizobium caulinodans from stem nodules of leguminous emergent hydrophyte Aeschynomene aspera.

The Azorhizobium caulinodans isolated from the stem nodules of a leguminous emergent hydrophyte, Aeschynomene aspera, produced a large amount of extracellular polysaccharides (EPS) in yeast extract basal medium. Maximum EPS production was at the stationary phase of growth. EPS production was increased by 919% over control when the medium was supplemented with sucrose (1.5%), D-biotin (1 microgram/ml) and casamino acid (0.1%). EPS contained rhamnose and arabinose. Possible role of the azorhizobial EPS production in the stem nodule symbiosis is discussed.

Produccion de xantano por Xanthomonas campestris en un medio de cultivo no convencional / Xanthan production by Xanthomonas campestris in no-conventional culture medium

Se determinó que X. campestris vp. Ocumo, exhibió mayor capacidad para crecer y producir xantano que las otras dos variedades de X. campestris analizadas. Utiliza una amplia diversidad de fuentes de carbohidratos. Sin embargo, la cepa no produce el exopolisacárido cuando la fuente de carbohidrato proviente de materiales ricos en lignocelulosa. El Jarabe Glucosado FAVEPRO (JGF) fue la fuente de carbono con la que se logró el mayor rendimiento de xantano (23g/l) con la mayor viscosidad (7000 cps). Las condiciones óptimas de producción determinadas en fiolas de 1 L (volumen de trabajo 10 L) fueron las siguientes: 5 por ciento de azúcares totales, 0,05 por ciento de urea como fuente de nitrógeno, 0.5 por ciento de fosfato dipotásico, pH 7.5, 10 por ciento de inóculo, temperatura 30 grados Celsius, agitación entre 250-1000 rpm y aireación entre 0.3-1.0 vvm. X. campestris vp. Ocumo, fue también capaz de producir xantano (10g/l), y aumentar la viscosidad (hasta 1500 cps) de un medio basado en el extracto ácido soluble de corteza de yuca molida (EACY).

Slime producing Staphylococci from clinical specimens - a simple diagnostic test.

Coagulase negative Staphylococci are now being increasingly recognised as pathogens. Some strains produce a viscous extracellular material or slime. These strains are uniquely adapted for adherence to even smooth surfaces. Present study is a preliminary report of 101 isolates of coagulase negative Staphylococci from different clinical specimens. Forty three of these 101 isolates (42.5%) were slime producers. The percentage of slime producing Staphylococci ranged from 20% in peritoneal fluid to 66.6% in Cerebrospinal fluid. The test for slime production may have an important application in deciding the pathogenecity of the strains of coagulase negative Staphylococci and should be done routinely in a diagnostic laboratory.

Producción de gomas xánticas / Production of xanthan gums

En el período que va desde febrero has agosto de 1990, se realizó un relevamiento de Xanthomonas campestris en la zona de Luján, provincia de Buenos Aires, de 70 muestras de vegetales infectados. Se comprobó si las 50 cepas de Xanthomonas campestris obtenidas presentaban la capacidad de producir goma xantan, así como el porcentaje de conversión de sustrato en goma y el recuento de Xanthomonas campestris viables/ml de cultivo. Los mayores números de cepas productoras del polisacárido extracelular se obtuvieron de alfalfa. Asimismo, la Xanthomonas campestris pv. alfalfae presentó elevados números de células viables y porcentajes de conversión de glucosa en goma xántica

Pesquisa de imunocomplexos circulantes em pacientes com meninogococcemia / Research of circulating immune complex in patients with meningococcemia

Pesquisa de imunocomplexos circulantes foi realizada em 15 pacientes com meningococcemia apresentando complicaçöes alérgicas, empregando o método de precipitaçäo com polietilenoglicol. Os resultados foram expressos pela comparaçäo das densidades ópticas (DO) dos eluatos e caracterizaçäo do antígeno polissacarídico nos imunocomplexos. Os pacientes analisados com meningococcemia apresentaram densidades ópticas aumentadas (0,570 a 0,257), quando comparadas àquela obtida em 33 soros controles (0,108) provenientes de doadores de Banco de Sangue. Foi possível em 12 casos a recuperaçäo do antígeno polissacarídico da N. meningitidis destes complexos através da dissociaçäo ácida e identificaçäo pela reaçäo de inibiçäo de hemaglutinaçäo