Bulent Icgen

Regulation of crystal protein biosynthesis by Bacillus thuringiensis: II. Effects of carbon and nitrogen sources

The regulation of crystal protein production in Bacillus thuringiensis 81 by sources of carbon and nitrogen was investigated. The highest titers of toxin were obtained on sucrose, lactose and inulin which also supported sporulation. Whey and molasses were also potential carbon substrates for toxin production. Other carbohydrates including glucose, glycerol, maltose, starch and dextrin yielded lower amounts of toxin. Nitrogen sources were found to exert the most profound controls. Peptone was the best organic nitrogen source, supporting optimum production and sporulation as well as high cell density. The formation of CryI and CryII toxin proteins was found to be differentially regulated by the inorganic nitrogenous compounds incorporated into the medium.

Multidrug and Heavy Metal-Resistant Raoultella planticola Isolated from Surface Water

A surface water isolate of Raoultella sp. having both multidrug- and multimetal-resistant ability was isolated and identified as Raoultella planticola. R. planticola displayed resistance to 15 drugs like ampicillin, amoxicillin/clavulanic acid, aztreonam, erythromycin, imipenem, oxacillin, pefloxacin, penicillin, piperacillin, piperacillin/tazobactam, rifampin, sulbactam/cefoperazone, ticarsillin, ticarsillin/clavulanic acid, vancomycin, and to 11 heavy metals like aluminum, barium, copper, iron, lead, lithium, manganese, nickel, silver, strontium, and tin. The multidrug and multi-metal-resistant R. planticola may remain present in the environment for a long time. Due to a possible health risk of these pathogenic bacteria, a need exists for an accurate assessment of their acquired resistance to multiple drugs and metals.

Regulation of crystal protein biosynthesis by Bacillus thuringiensis: I. Effects of mineral elements and pH.

Crystal protein synthesis by a local isolate of Bacillus thuringiensis was monitored and compared in association with growth and sporulation in media differing in mineral element content. Mg and Cu were the most important metals for the biosynthesis of 135 kDa and 65 kDa toxin components in that the former was essential and the latter was greatly stimulatory at 10(-6) to 10(-7) M concentration. Also the inclusion of Mn favored toxin production at concentrations ranging from 3 x 10(-4) to 10(-5) M. The omission of Zn and Ca had no effect on toxin formation. Crystal protein synthesis and sporulation did not generally seem to be co-regulated by the minerals as these processes responded differently to mineral levels. There was no evidence for suppression of biosynthesis by inorganic phosphate over a range of 3 to 100 mM. Crystal protein production was more efficient in buffered medium, especially when the initial pH was adjusted to 6.5.

Evaluation of symbiotic effectiveness of various Rhizobium cicer strains.

Five local and seven standard strains of Rhizobium cicer were compared in terms of their efficiency in increasing the nitrogen content of the chickpea. Shoot dry weight, nodule number, nodule dry weight, protein and total nitrogen contents were taken as the parameters of plant productivity. Different combinations of the strains that were found to be promising (385, 620, Y-29 and 3379) were next employed. The maximum increase in total nitrogen content was only 3.5-fold in single infection whereas an increase as great as 35-fold was recorded for multiple infections. The double infection with Y-29 and 385 as well as the triple infection with Y-29, 620 and 3379 gave rise to the maximum values. Competitiveness of the strains in mixed infections was determined through their recovery from root surfaces and nodules and their subsequent identification. The effects of soil pH and of varying the concentration of some minerals on the outcome of symbiosis were also reported.

Surface water isolates of hemolytic and non-hemolytic Acinetobacter with multiple drug and heavy metal resistance ability

Acinetobacter in surface waters are a major concern because of their rapid development of resistance to a wide range of antimicrobials and their ability to persist in these waters for a very long time. Four surface water isolates of Acinetobacter having both multidrug- and multimetal-resistant ability were isolated and identified through biochemical tests and 16S rDNA sequencing. Based on these analyses, two hemolytic isolates were affiliated with Acinetobacter haemolyticus with an accession number of X81662. The other two non-hemolytic isolates were identified as Acinetobacter johnsonii and Acinetobacter calcoaceticus and affiliated with accession numbers of Z93440 and AJ888983, respectively. The antibiotic and heavy metal resistance profiles of the isolates were determined by using 26 antibiotics and 17 heavy metals. Acinetobacter isolates displayed resistance to β-lactams, cephalosporins, aminoglycosides, and sulfonamides. The hemolytic isolates were found to show resistance to higher numbers of heavy metals than the non-hemolytic ones. Due to a possible health risk of these pathogenic bacteria, a need exists for an accurate assessment of their acquired resistance to multiple drugs and metals.

Biochemical and Molecular Characterization of Strontium-resistant Environmental Isolates of Pseudomonas fluorescens and Sphingomonas paucimobilis

Strontium resistance was investigated in strains isolated from the river Kızılırmak which has been affected by industrial and agricultural heavy metal pollution from the surrounding facilities and domestic effluents from the city Kırıkkale, Turkey. Strontium-resistant isolates with a minimal inhibitory concentration of 2000 mg L−1 were isolated and identified as Pseudomonas fluorescens and Sphingomonas paucimobilis. Both isolates were shown to be resistant to other heavy metals like aluminum, lithium, barium, nickel and resistance to the antibiotics like aztreonam and pefloxacin. Plasmid DNA analysis, transformation and curing results revealed that the strontium resistance ability of both isolates was chromosome-encoded. Outer membrane and total protein isolation results descriptively showed that not only membrane porins but also other proteins were effective in the strontium resistance in Pseudomonas fluorescens and Sphingomonas paucimobilis.

Challenging tin toxicity by a novel strain isolated from freshwaters

AbstractThe first major challenge for the bioremediation field is to select the most promising types of biomass. Hence, the objective of this study was to isolate and identify a novel species which has the potential to remediate tin in freshwaters. For this reason, a bacterium designated as Sn11, with 59 μg ml−1 maximum tolerable concentration of tin was isolated selectively from the freshwater samples collected along the river Kirikkale-Kizilirmak, Turkey. Identification of the isolate was done using biochemical tests, fatty acid methyl ester analysis, and 16S rRNA sequencing. Fatty acids produced by the isolate investigated were assumed as typical for the genus Pantoea. Pantoea were highly homogeneous by dominant C16:0 and C16:1 cis 9 fatty acids. 16S rRNA sequence analysis also confirmed that the isolate Sn11 had 98% homology with Pantoea agglomerans. The complete sorption of 59 μg ml−1 tin by P. agglomerans was recorded at about 20 h incubation. Due to higher affinity toward tin sorption, P. agglomera...

Surface water-borne multidrug and heavy metal-resistant Staphylococcus isolates characterized by 16S rDNA sequencing.

Abstract Four Staphylococcus isolates having both multidrug- and multimetal-resistant ability were isolated from surface water. Further identification of the isolates was obtained through biochemical tests and 16S rDNA gene sequencing. One methicillin-resistant and two methicilin-sensitive isolates were determined as Staphylococcus aureus. The other isolate was identified as Staphylococcus warneri. The antibiotic and heavy metal resistance profiles of the Staphylococcus isolates were determined by using 26 antibiotics and 17 heavy metals. S. aureus isolates displayed resistance to most of the β-lactam antibiotics tested. All Staphylococcus isolates were resistant to heavy metals including silver, lithium, and barium. Due to a possible health risk of these pathogenic bacteria, a need exists for an accurate assessment of their acquired resistance to multiple drugs and metals.

Colicinogeny in local isolates of salmonellae and plasmid transfer studies

Colicinogeny was determineed in local isolates ofS. typhimurium andS. enteritidis. Fourteen out of 35S. typhimurium isolates of hospital origin were colicin producers whereas only one chicken isolate out of 82S. enteritidis isolates of various origin (human, chicken or egg) produced colicin. A colicin producing, cephalothin (Cpt)- and piperacillin (Prl)-resistant local isolate ofSalmonella havana (H32) harbored 4 plasmids of 54.0, 28.4, 2.7 and 1.9 kb. Upon curing its plasmids, the strain lost the ability to produce colicin and resistance to antibiotics and no longer expressed smooth lipopolysaccharide (LPS). The outer membrane protein (OMP) of 34.6 kDa was also lost. Using nalidixic acid (Nal)-resistant mutant of the cured strain in conjugation experiments, 10 out of 27 transconjugants were found to be resistant to Nal and Prl, 10 were resistant to Nal and Cpt and 7 showed Nal, Prl and Cpt resistance. Cpt and Prl resistance were determined by 54.0 and 28.4 kb plasmids, respectively. There was no direct correlation between plasmid contents and colicinogeny, LPS and OMP profiles.

vanA Gene Harboring Enterococcal and Non-enterococcal Isolates Expressing High Level Vancomycin and Teicoplanin Resistance Reservoired in Surface Waters

Untreated wastewaters and treated effluents even after final disinfection contain antibiotic resistant bacteria and resistance genes before they are released into surface waters. A correlation between resistant bacteria and antibiotics in surface waters has been found, as have antibiotic resistance genes. Of particular interest are vancomycin-resistant enterococci harboring vanA gene that confers high level of resistance to glycopeptide antibiotics including teicoplanin. Therefore, in this study, river water samples were analysed to investigate vancomycin- and teicoplanin-resistant bacterial isolates harboring vanA gene. Out of 290, 15 surface water isolates displayed resistance to both antibiotics. These glycopeptide resistant enterococcal and non-enterococcal isolates, identified by 16S rRNA sequencing, were found to harbor vanA gene with sequence similarities of 50 % to 100 %. The presence of d-alanine-d-lactate ligase encoded by vanA gene was also shown for all vancomycin- and teicoplanin-resistant isolates through western blot analysis. Due to reuse of treated wastewater and release of untreated wastewaters to water bodies, antibiotic resistant bacteria and resistance genes are being introduced into surface waters and present human health risks. Therefore, surface waters are not only hot spots for vanA harboring enterococcal isolates but also non-enterococcal isolates due to gene dissemination and require special scientific consideration.