Proteomic Analysis of Salmonella-modified Membranes Reveals Adaptations to Macrophage Hosts

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Highlights

• •Affinity-based proteomics of infected macrophage cells.
• •Salmonella-modified membranes exhibit host-specific composition.
• •Proteome differences explain some host-dependent pathophysiological differences.

     

Isolation of microbes associated with field-collected populations of the egg parasitoid,Trichogramma chilonis capable of enhancing biotic fitness

Four bacterial and one yeast species, cultured and identified as Stenotrophomonas maltophilia, Acinetobacter sp., Pseudomonas sp. and Ochrobactrum sp. and the yeast as Metschnikowia reukaufii, were isolated from the internal organs of four collections of field-sourced egg parasitoid, Trichogramma chilonis, obtained as parasitised Helicoverpa armigera eggs. Bacteria were identified through 16 rRNA amplification and sequencing. The single species of yeast was identified through internal transcribed spacer sequences. A single bacterial species could be isolated from each of the four T. chilonis collections; however, all four T. chilonis collections yielded the yeast, M. reukaufii. In order to study the influence of the association of each of the bacterial species and the yeast, microbe-free laboratory-bred populations of T. chilonis were fed with the individual cultures and fitness parameters as parasitisation vigour and female bias were studied in T. chilonis over 10 generations. T. chilonis fed with either S. maltophilia or Acinetobacter sp. and Pseudomonas sp. showed a mean percent increase in female ratio of 26.2%, 30% and 30.3% and mean percent parasitisation of H. armigera eggs significantly increased by 38%, 32.2% and 31.3%, respectively. However, T. chilonis fed with Acinetobacter sp. did not positively influence the two T. chilonis fitness factors. The ubiquitous yeast, M. reukaufii, which could be isolated from all four collections of T. chilonis, could significantly increase both female count and percent parasitism ratio by 22% and 65%, respectively. This study has opened the possibility of modulating the parasitisation fitness of laboratory-bred T. chilonis, prior to field release, using microbes associated with them in the wild.     

Antibacterial activities of the methanol extracts of Canarium schweinfurthii and four other Cameroonian dietary plants against multi-drug resistant Gram-negative bacteria

Bacterial infections are among the major cause of morbidity and mortality worldwide. The present study was designed to evaluate the in vitro antibacterial activities of the methanol extracts of five Cameroonian edible plants namely Colocasia esculenta, Triumfetta pentandra, Hibiscus esculentus, Canarium schweinfurthii and Annona muricata against a panel of 19 multidrug resistant Gram-negative bacterial strains. The liquid broth microdilution was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the extracts. The preliminary phytochemical screening of the extracts was conducted according to the standard phytochemical methods. Results showed that all extracts contained compounds belonging to the classes of polyphenols, triterpenes and steroids, other classes of chemicals being selectively distributed. Canarium schweinfurthii extract showed the best activity with MIC values ranging from 64 to 1024 μg/mL against 89.5% of the 19 tested bacteria strains. MIC values below or equal to 1024 μg/mL were also recorded with Triumfetta pentandra, Annona muricata, Colocasia esculenta and Hibiscus esculentus extracts respectively against 15/19 (78.9%), 11/19 (57.9%), 10/19 (52.6%) and 10/19 (52.6%) tested bacteria. Extract from C. schweinfurthii displayed the lowest MIC value (64 μg/mL) against Escherichia coli AG100A_Tet. Finally, the results of this work provide baseline information for the use of C. esculenta, T. pentandra, H. esculentus, C. schweinfurthii and A. muricata in the treatment of bacterial infections including multidrug resistant phenotypes.     

Phylogenetic position of Gluconobacter species as a coherent cluster separated from all Acetobacter species on the basis of 16S ribosomal RNA sequences

Abstract The 16S rRNA sequences from the Gluconobacter species G. asaii G. cerinus and G. frateurii were determined and compared with homologous sequences from published databases and sequences of G. oxydans and Acetobacter species previously described [Sievers M., Ludwig W. and Teuber M. (1994) System. Appl. Microbiol. 17, 189–196]. The Gluconobacter species have unique 16S rRNA sequences and exhibit sequence similarity values of 97.4 to 99.1%, corresponding to 36 to 14 base differences. The phylogenetic tree inferring methods (distance matrix, maximum parsimony and maximum likelihood) show that the species of Gluconobacter form a coherent, closely related cluster. Based on the distance matrix method including Rhodopila globiformis as an outgroup reference organism, Gluconobacter is well separated from Acetobacter .     

Nickel resistance in Escherichia coli V38 is dependent on the concentration used for induction

Strain Escherichia coli V38 resistant to 4 mM NiCl₂ was isolated from the city sewage sludge. It showed low nickel accumulation by cells and nickel ion efflux. Cells were pregrown (induced) overnight in the presence of Ni²⁺, then the culture was kept on ice for 20–30 min and transferred to 37°C for further incubation. When the Ni²⁺ concentration during growth was the same as during incubation, there was no noticeable accumulation of Ni²⁺. When the Ni²⁺ concentration during incubation was higher than that used for induction, uptake of ⁶³Ni²⁺ and delayed efflux were seen. The uptake and delay of both efflux and growth were directly proportional to the difference between the concentrations used for induction and incubation. Active nickel ion uptake was seen in cells taken from cultures in the delayed efflux period.     

Conversion of two distinct Rhodopseudomonas capsulata isolates to the glycerol-utilizing phenotype

Abstract Previous studies employing a single strain of the photosynthetic bacterium Rhodopseudomonas capsulata have demonstrated that this organism, which normally is not capable of growth on glycerol, can gain glycerol-utilizing ability through mutational events. We have examined other strains of R. capsulata of divergent geographic origin, and have found that they could also be converted to a glycerol-catabolic phenotype. Mutant derivatives were found to express high constitutive levels of glycerophosphate dehydrogenase (GPD) and glycerokinase (GK) which were barely detectable in the parental strains. These results suggest that the ability to utilize glycerol after undergoing a gain of function mutation is a widespread property of R. capsulata .     

五株乳酸菌和三株芽孢杆菌的生物学特性和功能

【背景】乳酸菌和芽孢杆菌是应用于生产最多的益生菌,但不同菌株间的生长特性均不相同,因此了解菌株的生物学特性具有重要意义。【目的】研究菌株的生物学特性,能合理地开发和利用菌株,以保证菌株生产应用的安全性。【方法】活化后鉴定5株乳酸菌和3株芽孢杆菌并对其形态进行观察,探究菌株的生长曲线、产酸能力及最适生长条件,测定菌株的抑菌活性和产酶性能,同时探究菌株的益生性和安全性。【结果】五株乳酸菌分别编号鉴定为干酪乳杆菌R1、副干酪乳杆菌R2、香肠乳杆菌R3、福莱乳杆菌R4和唾液乳杆菌R5;3株芽孢杆菌分别编号命名为贝莱斯芽孢杆菌Y1、枯草芽孢杆菌Y2和地衣芽孢杆菌Y3。八株菌形态结构均不相同但都为杆状,均在2–10 h为对数生长期,18–24 h为稳定期,培养24 h时乳酸菌和芽孢杆菌的活菌数均保持在10⁹和10⁸ CFU/mL,最适生长温度为37.0℃。乳酸菌具有较强的产酸能力和抑菌活性,芽孢杆菌有较强的产酶性,在人工胃液中都有较强的耐受性。八株菌都无溶血活性、无毒力基因、对抗生素都保持中度敏感以上;其中唾液乳杆菌有四环素耐药基因,但对四环素抗性为中度敏感。【结论】八株菌生长繁殖速度快,乳酸菌产酸能力和抑菌活性较强,芽孢杆菌具有较强的产酶性能,在体外具有较好的益生性和安全性,可应用于生产实践。     

荒漠草原盐沼湿地苦豆子土壤细菌群落构建机制及其影响因素

【背景】荒漠草原盐沼湿地是陆地生态系统的重要组成部分,土壤水分和盐分变化是影响该生态系统土壤细菌群落构建的重要因素。【目的】土壤细菌群落构建是由确定性和随机性主导的连续生态过程,阐明荒漠草原盐沼湿地土壤细菌群落的构建机制对于加深微生物作为关键生态系统因子重要性的理解具有积极意义。【方法】以宁夏中部典型荒漠草原盐沼苦水湖湿地为研究对象,对近湖边（near the lake,NL）和远离湖边（far from the lake,FL）苦豆子群落土壤理化特性进行测定并结合土壤细菌高通量测序分析。【结果】NL和FL样地具有明显的水盐梯度变化,NL样地土壤pH、含水量和电导率均显著高于FL样地;变形菌门、放线菌门、厚壁菌门、拟杆菌门和黏菌门是研究区域土壤细菌群落的优势菌门,变形菌门相对丰度随水盐梯度上升而升高,放线菌门和厚壁菌门相对丰度则随之下降,门下成员大多与水盐变化具有明显的相关性;此外,FL样地土壤细菌网络则具有稳定的网络关系;随着NL样地向FL样地的延伸,土壤细菌群落由随机过程主导,并且受pH、电导率和环境变量的影响。【结论】荒漠草原盐沼湿地水分和盐分的变化改变了土壤细菌群落结构;土壤细菌群落通过生态位占据等策略提高逆境下的生存能力;细菌群落构建是随机过程和确定性过程组成的连续统一体,同样受环境变化的影响。本结果揭示了荒漠草原盐沼湿地细菌群落结构和相互关系对环境变化的响应特征,同时阐明了该区土壤细菌群落的构建机制及影响因素,也为相关科学研究提供了一定理论参考。     

Cytotoxic Spliceostatin Analogs from Pseudomonas sp.

Two new spliceostatin analogs, designed as spliceostatins J and K ( 1 and 2 ), were isolated and identified from the culture of Pseudomonas sp., along with two known ones, FR901464 ( 3 ) and spliceostatin E ( 4 ). Their structures were elucidated by detailed interpretation of their spectroscopic data, especially 2D‐NMR and HR‐ESI‐MS. Spliceostatin J ( 1 ) represented the first example of spliceostatins bearing an unusual hexahydrofuro[3,4‐b]furan moiety. Biological assay showed all the isolated compounds except 1 displayed potent cytotoxic activities against two cancer cell lines (MDA‐MB‐231 and A‐549). Structure‐activity‐relationship studies revealed that the tetrahydropyran ring in spliceostatin analogs was necessary for their bioactive retention.