Conformation of di-n-propylglycine residues (Dpg) in peptides: crystal structures of a type I' beta-turn forming tetrapeptide and an alpha-helical tetradecapeptide.

The crystal structures of two oligopeptides containing di-n-propylglycine (Dpg) residues, Boc-Gly-Dpg-Gly-Leu-OMe (1) and Boc-Val-Ala-Leu-Dpg-Val-Ala-Leu-Val-Ala-Leu-Dpg-Val-Ala-Leu-OMe (2) are presented. Peptide 1 adopts a type I'beta-turn conformation with Dpg(2)-Gly(3) at the corner positions. The 14-residue peptide 2 crystallizes with two molecules in the asymmetric unit, both of which adopt alpha-helical conformations stabilized by 11 successive 5 --> 1 hydrogen bonds. In addition, a single 4 --> 1 hydrogen bond is also observed at the N-terminus. All five Dpg residues adopt backbone torsion angles (phi, psi) in the helical region of conformational space. Evaluation of the available structural data on Dpg peptides confirm the correlation between backbone bond angle N-C(alpha)-C' (tau) and the observed backbone phi,psi values. For tau > 106 degrees, helices are observed, while fully extended structures are characterized by tau < 106 degrees. The mean tau values for extended and folded conformations for the Dpg residue are 103.6 degrees +/- 1.7 degrees and 109.9 degrees +/- 2.6 degrees, respectively.     

Stimulatory effect of honey on multiplication of lactic acid bacteria under in vitro and in vivo conditions

The effect of honey and sucrose on lactic acid bacteria in vitro and in rat gut was studied to determine whether these organisms were affected differently by honey compared with sucrose. Under in vitro conditions, the number of Lactobacillus acidophilus and Lactobacillus plantarum counts increased 10-100 fold in the presence of honey compared with sucrose. Feeding of honey to rats also resulted in significant increase in counts of lactic acid bacteria. Although there was no significant difference in the counts of lactic acid bacteria in the small and large intestines of different groups, the honey-fed group showed a significant increase (P<0.05) in counts over the control and sucrose-fed animals. The results support the fact that consumption of honey has a beneficial effect on the physiological constitution of animals fed with it.     

Peptide mimotopes of complex carbohydrates in Salmonella enterica serovar typhi which react with both carbohydrate-specific monoclonal antibody and polyclonal sera from typhoid patients

Polyclonal sera from typhoid patients and a monoclonal antibody, mAb ATVi, which recognizes the capsular polysaccharide Vi antigen (ViCPS), were used to select for peptides that mimic the ViCPS by using a phage-displayed random 12-mer peptide library. Two major common mimotopes selected from the library carried the amino acid sequences TSHHDSHGLHRV and ENHSPVNIAHKL. Enzyme-linked immunosorbent assays (ELISAs) showed that these peptides carry mimotopes to ViCPS. Phage clones that contained the 12-mer peptides were also tested against pooled/individual typhoid patients' sera and found to have 3 to 5 times higher binding compared to normal sera. By using Phage-ELISA assays, the derived synthetic peptides, TSHHDSHGLHRV and ENHSPVNIAHKL, were tested against a monoclonal antibody mAb ATVi and over 2-fold difference in binding was found between these peptides and a control unrelated peptide, CTLTTKLYC. Inhibition of the mAb's binding to ViCPS indicated that the synthetic peptides successfully competed with the capsular polysaccharide for antibody binding.     

Detection of methicillin- and aminoglycoside-resistant genes and simultaneous identification of S. aureus using triplex real-time PCR Taqman assay

In this study we describe a triplex real-time PCR assay that enables the identification of S. aureus and detection of two important antibiotic resistant genes simultaneously using real-time PCR technology in a single assay. In this triplex real-time PCR assay, the mecA (methicillin resistant), femA (species specific S. aureus) and aacA-aphD (aminoglycoside resistant) genes were detected in a single test using dual-labeled Taqman probes. The assay gives simultaneous information for the identification of S. aureus and detection of methicillin and aminoglycoside resistance in staphylococcal isolates. 152 clinical isolates were subjected to this triplex real-time PCR assay. The results of the triplex real-time PCR assay correlated with the results of the phenotypic antibiotic susceptibility testing. The results obtained from triplex real-time PCR assay shows that the primer and probe sets were specific for the identification of S. aureus and were able to detect methicillin- and aminoglycoside-resistant genes. The entire assay can be performed within 3 h which is a very rapid method that can give simultaneous information for the identification of S. aureus and antibiotic resistance pattern of a staphylococcal isolate. The application of this rapid method in microbiology laboratories would be a valuable tool for the rapid identification of the S. aureus isolates and determination of their antibiotic resistance pattern with regards to methicillin and aminoglycosides.     

Studies on Scenedesmus acutus growth II. Effect of autotrophic and mixotrophic growth on the amino acid and the carbohydrate composition of Scenedesmus acutus

As a general rule an increase in carbohydrates occurs during the light phase of the cell cycle and that of protein during phase, although variations were found in these components under autotrophic and mixotrophic growth conditions. The results are based on the quantitative determination of carvohydrates as trimethylsilyl (TMS) derivatives and amino acids as N-trifluoroacetyl-n-butyl (TAB) esters in algal cells cultured in light and dark periods by gas-liquid chromatography (LC). Cells harvested during the dark period contained more amino acids as compared to similar cultures harvested during the light phase. In light, the production of amino acids of the aspartate family increased in cells cultivated with glucose and carbon dioxide. With glucose as sole carbon source, the carbohydrate content was higher in the dark than in the light period. Under continuous light conditions, in the presence of carbon dioxide, there was a decrease in the carbohydrate content also. Gas-liquid chromatography analysis of the extract of the purified cell walls showed that they are made up of 0.076% carbohydrates and 0.28% amino acids on the dry weight (DW) basis of whole cells. The results on the metabolism of cells, under autotrophic and mixotrophic conditions, are discussed in this article.     

Symbiotic interaction of endophytic bacteria with arbuscular mycorrhizal fungi and its antagonistic effect on Ganoderma boninense

Endophytic bacteria (Pseudomonas aeruginosa UPMP3 and Burkholderia cepacia UMPB3), isolated from within roots of oil palm (Elaeis guineensis Jacq.) were tested for their presymbiotic effects on two arbuscular mcorrhizal fungi, Glomus intraradices UT126 and Glomus clarum BR152B). These endophytic bacteria were also tested for antagonistic effects on Ganoderma boninense PER 71, a white wood rot fungal pathogen that causes a serious disease in oil palm. Spore germination and hyphal length of each arbuscular mycorrhizal fungal (AMF) pairing with endophytic bacteria was found to be significantly higher than spores plated in the absence of bacteria. Scanning electron microscopy (SEM) showed that the endophytic bacteria were scattered, resting or embedded on the surface hyaline layer or on the degraded walls of AMF spores, possibly feeding on the outer hyaline spore wall. The antagonistic effect of the endophytic bacteria was expressed as severe morphological abnormalities in the hyphal structures of G. boninense PER 71. The effects of the endophytic bacteria on G. boninense PER 71 hyphal structures were observed clearly under SEM. Severe inter-twisting, distortion, lysis and shriveling of the hyphal structures were observed. This study found that the effect of endophytic bacteria on G. intraradices UT126 and G. clarum BR152B resembled that of a mycorrhiza helper bacteria (MHB) association because the association significantly promoted AMF spore germination and hyphal length. However, the endophytic bacteria were extremely damaging to G. boninense PER 71.     

Isolation of polyhydroxyalkanoate from hydrolyzed cells of <Emphasis Type="Italic">Bacillus flexus</Emphasis> using aqueous two-phase system containing polyethylene glycol and phosphate

Main objective of present work was to isolate polyhydroxyalkanoate (PHA) from cell lysate of Bacillus flexus by aqueous-aqueous two-phase system (ATPS). Selected ATPS having polyethylene glycol (12%, w/v) and potassium phosphate (9.7%, pH 8.0) containing cell lysate obtained by sonication or hypochlorite treatment of B. flexus biomass (1 g%, dry weight), was held at 28°C for 30 min, which partitioned PHA into top PEG phase and residual cell materials into bottom phase. For enzymatic cell hydrolysis, Microbispora sp. culture filtrate having protease (3 U/mL) was mixed with B. flexus biomass and ATPS, incubated at 37°C for 2 h prior to phase separation. PHA recovered by centrifugation was 19∼51% of cell dry weight, depending on the mode of cell disruption. Protease was recovered along with PHA in the PEG phase and showed 7 fold increase in activity. PHA was characterized by GC, FTIR, and ¹H NMR. Results indicated that ATPS can be used for the isolation of PHA from hydrolyzed bacterial cells and purified protease can be recovered as a byproduct, in a single defined experiment. Results have indicated that ATPS can be successfully employed as a non-organic solvent method for the isolation of PHA.     

Use of wheat bran as a nutritive supplement for the production of ethanol by Zymomonas mobilis

A strain of Zymomonas mobilis (ZYM-TS 1) was isolated from fermenting palm wine (toddy). In addition to glucose, sucrose, and fructose, the organism utilized hydrolysates of corn ( Zea mays ) flour, corn starch and ragi ( Eleusine coracana ) flour. Amounts of ethanol produced in media (adjusted to 10% (w/v) total carbohydrates) fortified with wheat bran extract only, were comparable with those obtained from the defined media containing yeast extract, (NH₄)₂SO₄, KH₂PO₄, and MgSO₄.7H₂O. The results indicate that wheat bran extract can supply all the necessary nutrients required for ethanol production by Zymomonas mobilis .     

Antigenic relationship between reactivity to hepatitis B e antigen and 19 kDa protein ofMycobacterium tuberculosis among the Tibetan settlers in Karnataka

McGlynn and her co-workers have reported that among the Vietnamese refugees in Philadelphia and among Alaskan natives who are hepatitis B carriers, there is a statistically significant association between anegative tuberculin test and the presence of hepatitis B e antigen. A repetition of this work among the population of Bangalore did not yield any significant results because of the very low incidence of hepatitis found among this population. However, on the basis of available data that hepatitis B infection is more prevalent among the Mongolian population than among people of other populations, the work was repeated among Tibetans who had settled down in Karnataka. This set of experiments showed that, contrary to the report of McGlynnet al, there is a statistically significant association between apositive tuberculin test and the presence of hepatitis B e antigen and that those individuals who showed the presence of hepatitis B e antigen exhibited less severe form of the disease than those who were negative to this antigen. These findings suggested that immunity to tuberculosis and hepatitis B infections may have a common underlying principle. Data bank search revealed a stretch of amino acid sequences which is common to hepatitis B e antigen and 19 kDa antigen ofMycobacterium tuberculosis. The significance of these results is discussed.