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PubMed1993

Bacitracin production by a new strain of Bacillus subtilis. Extraction, purification, and characterization.

A new strain of Bacillus subtilis C 126 was isolated from sugar cane fermentation and produced an antibiotic that inhibited the growth of Micrococcus flavus. The production of the antibiotic in culture medium followed to extraction with n-butanol, thin layer chromatography, and microbiological tests indicated that a polypeptide antibiotic was produced. The fraction obtained by Sephadex G-25 column and analyzed by HPLC indicated that bacitracin complex was produced.

1-Butanol↗
PubMed1993

Antimicrobial activity determined in strains of Bacillus circulans cluster.

Wild-type strains of the genus Bacillus were screened for antimicrobial activity. Two strains exhibited antimicrobial activity against Micrococcus luteus and were identified as Bacillus polymyxa MIR-23 and Bacillus circulans MIR-13. Bacillus polymyxa MIR-23 was active against Escherichia coli, Pseudomonas aeruginosa and Aspergillus niger, whereas Bacillus circulans MIR-13 did not show activity against these microorganisms. Bacillus subtilis ATCC 6633 and B. polymyxa ATCC 10401 were used as standard antibiotic-producer strain and showed different antimicrobial profiles and yields from B. polymyxa MIR-23. The different antimicrobial profile of the two selected strains could possibly be used as a taxonomic marker.

Anti-Bacterial Agents↗
PubMed1998

Experimental biofilm and its application in malathion degradation.

Mixed bacterial culture consisting of three different strains of Micrococcus sp. (AG 36, AG 94 and AG 98) and two strains of Pseudomonas sp. (AG 7 and AG 52) and its individual components was passed through a sand column and 25.5-92% of cell dry mass was found to be retained (adsorbed) on it. Incubation of sand soaked in mineral medium containing glucose as a sole carbon source resulted in formation of a biofilm with 1.2-2.5-fold increase in biomass. A 61% degradation of malathion by the mixed culture biofilm could be achieved in 4 d.

Bacterial Adhesion↗
PubMed1976

Amidase activity of some bacteria.

The amidase activity of bacteria possessing a high nitrilase activity was found to display the same spectrum although the bacteria may belong to different taxonomic groups, Bacillus, Bacteridium, Micrococcus, Brevibacteriun. The spectrum of amidase activity, although very broad, is more restricted than that of nitrilase activity. Internal amides as well as vinyl-bound amides are not hydrolyzed.

Amides↗
PubMed2000

Ultrastructure of two oil-degrading bacteria isolated from the tropical soil environment.

Two oil-degrading bacteria identified as Pseudomonas aeruginosa and Micrococcus luteus were isolated from crude-oil-polluted soils in Nigeria. The organisms were grown on n-hexadecane and sodium succinate and then examined for the presence of hydrocarbon inclusions. Inclusion bodies were found in n-hexadecane-grown cells and were absent in succinate-grown cells. Formation of hydrocarbon inclusion bodies appears to be a general phenomenon among hydrocarbon utilizers.

Alkanes↗
PubMed1981

Mutation modifying the serine pathway in methylotrophic bacteria.

Methylotrophic bacteria, Gram-positive, with the serine pathway, were shown to have their growth inhibited by 0.5% glycine. The effects of this amino acid on individual enzyme activities were studied in wild and mutant strains of Micrococcus varians and Bacillus licheniformis. The enzymes studied were glycerate dehydrogenase (EC 1.1.1.29), isocitrate lyase (EC 4.1.3.1), serine hydroxymethyltransferase (EC 2.1.2.1) and glycine--oxaloacetate aminotransferase (EC 2.6.1.35). The last-named enzyme was found to be inhibited, the kinetic constants having been determined for two strain types.

Bacillus↗
PubMed1985

Antimicrobial effect of sugar osazones and anhydro sugars.

The antimicrobial effect of 14 sugar osazones and anhydro sugars was studied with model strains of Micrococcus luteus, Bacillus licheniformis, Escherichia coli and strains Staphylococcus aureus and Pseudomonas aeruginosa isolated from clinical material. The relationship between the structure of these compounds, their solubility in water and 1-octanol and antimicrobial effect was investigated.

Bacillus↗
PubMed2004

Synthesis and study of antibacterial and antifungal activities of novel 2-[[(benzoxazole/benzimidazole-2-yl)sulfanyl] acetylamino]thiazoles.

Several 2-[[(benzoxazole/benzimidazole-2-yl)sulfanyl]acetylamino]thiazoles derivatives were synthesized by reacting 4-substituted-2-(chloroacetylamino)thiazoles with benzoxazole/benzimidazole-2-thioles in acetone and in the presence of K2CO3. The chemical structures of the compounds were elucidated by IR, 1H-NMR, and FAB(+)-MS spectral data. Their antimicrobial activities against Micrococcus luteus (NRLL B-4375), Bacillus cereus (NRRL B-3711), Proteus vulgaris (NRRL B-123), Salmonella typhimurium (NRRL B-4420), Staphylococcus aureus (NRRL B-767), Escherichia coli (NRRL B-3704), Candida albicans and Candida globrata (isolates obtained from Osmangazi Uni. Fac.of Medicine) were investigated and in this investigation, a significant level of activity was illustrated.

Anti-Bacterial Agents↗
PubMed2004

Evaluation of agar diffusion bioassay for nisin quantification.

The agar diffusion bioassay is the most widely used method for the quantification of nisin, due to its high sensitivity, simplicity, and cost-effectiveness. This method is based on the measurement of the inhibition zone produced in nisin-sensitive microorganisms. The size of the zone is affected by many factors, such as nisin-sensitive strain, amount of added agar and surfactant, and pre-diffusion step. This research aims to evaluate the effects of nisin-sensitive strains and pre-diffusion on the accuracy and precision of nisin quantification. Three strains of nisin-sensitive microorganisms (Micrococcus luteus, Lactobacillus sakei, Brochothrix thermosphacta) were tested along with three different incubation processes. The best combination was the method using L. sakei as an indicator strain with pre-diffusion at 4 degrees C for 24 h. Compared with M. luteus and B. thermosphacta, L. sakei gave more accurate and reproducible results. Moreover, the pre-diffusion step resulted in larger inhibition zones and more precise results. Finally, the best combination was validated and compared with the method that is usually used and the result showed that the method using L. sakei with pre-diffusion gave more accurate and precise results.

Agar↗
PubMed2004

Site-directed mutagenesis of the hinge region of nisinZ and properties of nisinZ mutants.

To study the role of the hinge region in nisin and to obtain mutants that exhibit altered or new biological activities and functional properties, we changed certain amino acids in the hinge region by performing site-directed mutagenesis with the nisinZ structural gene ( nisZ). The results showed that the nisinZ mutants had decreased antimicrobial activities against Micrococcus flavus NCIB8166 and Streptococcus thermophilus. Interestingly, compared with wild nisinZ, mutant N20K nisinZ and M21K nisinZ displayed antimicrobial activity against gram-negative Shigella, Pseudomonas and Salmonella; and they had a higher solubility than wild-type nisinZ. At pH 8, the solubilities of N20K nisinZ and M21K nisinZ were, respectively, three-fold higher and five-fold higher than that of nisinZ. Mutant N20Q nisinZ and M21G nisinZ were considerably more stable than nisinZ at higher temperatures and neutral or alkaline pH. These mutants provided information that the central hinge region in nisinZ plays an important role in providing the conformational flexibility required for the antimicrobial activity on the membrane. Our finding documented that it may well be worth considering the construction of the new nisin mutants with changed inhibitory activity against a wide range of gram-negative bacteria and the improvement of functional properties by site-directed mutagenesis.

Amino Acid Sequence↗
PubMed2001

High-pressure adaptation by salt stress in a moderately halophilic bacterium obtained from open seawater.

High-pressure adaptation was examined using a moderately halophilic bacterium (Micrococcus roseus), which was isolated from open seawater and capable of growing in 15% w/v NaCl (optimum NaCl concentration: 3% w/v). After treatment at 207 MPa, colony-forming units (CFUs) significantly decreased; however, the loss of integral cells after pressure was only 30% when direct cell count was performed microscopically. In order to investigate the piezotolerance of M. roseus under high pressure without morphological change, the survival of cells was examined under pressure at 138 MPa for 2 h. M. roseus in 3% NaCl was still sensitive to pressure at 138 MPa. However, the cells in the third generations showed remarkably increased pressure resistance, and no significant loss of viability was confirmed. Furthermore, when M. roseus was cultured in 1, 3, 5, 10 and 15% NaCl, the survival ratio proportionally increased at increased NaCl concentration. M. roseus cultured in 15% NaCl was remarkably resistant (94.7% viability) to pressure at 138 MPa, even when suspended in lower concentration of NaCl. This suggests that NaCl concentrations in growth culture affect the piezotolerance of M. roseus and that this species has an ability to adapt to high pressure.

Adaptation, Physiological↗
PubMed2003

Hemocyte-mediated phagocytosis and melanization in the mosquito Armigeres subalbatus following immune challenge by bacteria.

Mosquitoes are important vectors of disease. These insects respond to invading organisms with strong cellular and humoral immune responses that share many similarities with vertebrate immune systems. The strength and specificity of these responses are directly correlated to a mosquito's ability to transmit disease. In the current study, we characterized the hemocytes (blood cells) of Armigeres subalbatus by morphology (ultrastructure), lectin binding, enzyme activity, immunocytochemistry, and function. We found four hemocyte types: granulocytes, oenocytoids, adipohemocytes, and thrombocytoids. Granulocytes contained acid phosphatase activity and bound the exogenous lectins Helix pomatia agglutinin, Galanthus nivalis lectin, and wheat germ agglutinin. Following bacteria inoculation, granulocytes mounted a strong phagocytic response as early as 5 min postexposure. Bacteria also elicited a hemocyte-mediated melanization response. Phenoloxidase, the rate-limiting enzyme in the melanization pathway, was present exclusively in oenocytoids and in many of the melanotic capsules enveloping bacteria. The immune responses mounted against different bacteria were not identical; gram(-) Escherichia coli were predominantly phagocytosed and gram(+) Micrococcus luteus were melanized. These studies implicate hemocytes as the primary line of defense against bacteria.

Acid Phosphatase↗
PubMed2000

Structural analysis of the elongation factor G protein from the low-temperature-adapted bacterium Arthrobacter globiformis SI55.

The first structural analysis of elongation factor G (EF-G) from a cold-adapted bacterium is presented. EF-G is an essential protein involved in the elongation process during protein synthesis and is therefore thought to play a crucial role in the low-temperature adaptation of cold-adapted microorganisms. To define its importance, the EF-G gene (fus) from the psychrotolerant bacterium Arthrobacter globiformis SI55 was cloned and sequenced. The deduced primary structure of the elongation factor is composed of 700 amino acids with a predicted molecular mass of 77.4 kDa. A three-dimensional model of the protein was constructed based on the known crystal structures of structurally homologous proteins. Structural features that might potentially be important for activity and flexibility at low temperature were deduced by comparisons with models of the EF-G proteins from the closely related mesophiles Micrococcus luteus and Mycobacterium tuberculosis. These features include a loss in the number of salt bridges in intradomain and interdomain positions, increased solvent interactions mediated by greater charge and polarity on domain surfaces, loop insertions, loss of proline residues in loop structures, and an increase of hydrophobicity in core regions. Specific changes have also been identified in the catalytic domain (G domain) and sites of potential ribosome interaction, which may directly affect guanosine triphosphate (GTP) hydrolysis and elongation rates at low temperature.

Amino Acid Sequence↗
PubMed2005

Characterization of salt-tolerant glutaminase from Stenotrophomonas maltophilia NYW-81 and its application in Japanese soy sauce fermentation.

Glutaminase from Stenotrophomonas maltophilia NYW-81 was purified to homogeneity with a final specific activity of 325 U/mg. The molecular mass of the native enzyme was estimated to be 41 kDa by gel filtration. A subunit molecular mass of 36 kDa was measured with SDS-PAGE, thus indicating that the native enzyme is a monomer. The N-terminal amino acid sequence of the enzyme was determined to be KEAETQQKLANVVILATGGTIA. Besides L: -glutamine, which was hydrolyzed with the highest specific activity (100%), L: -asparagine (74%), D: -glutamine (75%), and D: -asparagine (67%) were also hydrolyzed. The pH and temperature optima were 9.0 and approximately 60 degrees C, respectively. The enzyme was most stable at pH 8.0 and was highly stable (relative activities from 60 to 80%) over a wide pH range (5.0-10.0). About 70 and 50% of enzyme activity was retained even after treatment at 60 and 70 degrees C, respectively, for 10 min. The enzyme showed high activity (86% of the original activity) in the presence of 16% NaCl. These results indicate that this enzyme has a higher salt tolerance and thermal stability than bacterial glutaminases that have been reported so far. In a model reaction of Japanese soy sauce fermentation, glutaminase from S. maltophilia exhibited high ability in the production of glutamic acid compared with glutaminases from Aspergillus oryzae, Escherichia coli, Pseudomonas citronellolis, and Micrococcus luteus, indicating that this enzyme is suitable for application in Japanese soy sauce fermentation.

Amino Acid Sequence↗
PubMed2005

Novel actinobacteria from marine sponges.

Actinobacteria exclusively within the sub-class Acidimicrobidae were shown by 16S rDNA community analysis to be major components of the bacterial community associated with two sponge species in the genus Xestospongia. Four groups of Actinobacteria were identified in Xestospongia spp., with three of these four groups being found in both Xestospongia muta from Key Largo, Florida and Xestospongia testudinaria from Manado, Indonesia. This suggests that these groups are true symbionts in these sponges and may play a common role in both the Pacific and Atlantic sponge species. The fourth group was found only in X. testudinaria and was a novel assemblage distantly related to any previously sequenced actinobacterial clones. The only actinobacteria that were obtained in initial culturing attempts were Gordonia, Micrococcus and Brachybacterium spp., none of which were represented in the clone libraries. The closest cultured actinobacteria to all the Acidimicrobidae clones from Xestospongia spp. are 'Microthrix parvicella' and Acidimicrobium spp. Xestospongia spp. can now be targeted as source material from which to culture novel Acidimicrobidae to investigate their potential as producers of bioactive compounds. Isolation of sponge-associated Acidimicrobidae will also make it possible to elucidate their role as sponge symbionts.

Actinobacteria↗
PubMed2005

Host blood proteins and peptides in the midgut of the tick Dermacentor variabilis contribute to bacterial control.

Antimicrobial midgut proteins and peptides that result from blood digestion in feeding American dog ticks Dermacentor variabilis (Say) were identified. Midgut extracts from these ticks showed antimicrobial activity against Micrococcus luteus, regardless of whether they were challenged with peptidoglycan, blood meal components, rabbit blood, Bacillus subtilis, Escherischia coli or Borrelia burgdorferi. However, no peptide band co-migrating with defensin was found in midgut extracts from the challenged ticks. Partial purification of the midgut extracts using C(18) Sep Paks and gel electrophoresis showed the presence of 4 distinct bands with rMW 4.1, 5.3, 5.7 and 8.0 kDa identified by tryptic digestion-mass fingerprinting as digestive fragments of rabbit alpha-, beta-, gamma-chain hemoglobin, and rabbit ubiquitin. No evidence of varisin, a defensin previously identified in the hemolymph of D. variabilis, was found in the tryptic digest, although varisin was found in a hemocyte lysate using the same methods. However, varisin transcript was detected in midgut cell lysates. Also present in all midgut samples was a cluster of 3 overlapping bands with rMW 13.0, 14.1 and 14.7 kDa which were identified by tryptic-digestion LC-MS and MALDI-TOF as rabbit alpha- and beta-chain hemoglobin (undigested) and transtherytin. Lysozyme transcript was detected in midgut cell extracts but the peptide was not. Studies done on other tick species demonstrated that hemoglobin digestion resulted in antimicrobial fragments. Antimicrobial hemoglobin fragments (including fragments larger than any reported previously) also were found in D. variabilis, as well as ubiquitin, a peptide known to occur as part of an antimicrobial complex in vertebrate leukocytes. In addition, we noted that Borrelia burgdorferi spirochetes were not lysed in the midgut lumen, which would be expected if defensin and lysozyme were active in this location. In this respect, the midgut's response to microbial challenge differs from that of the hemolymph. In summary, the midgut's antimicrobial activity appears to be primarily a byproduct of hemoglobin digestion rather than expression of immune peptides and proteins.

Animals↗
PubMed2006

Recombinant expression of human cathelicidin (hCAP18/LL-37) in Pichia pastoris.

The constitutive expression of human cathelicidin LL-37 antimicrobial peptide was achieved using the methylotrophic yeast, Pichia pastoris. An LL-37 cDNA clone was amplified by PCR using human fetal cDNA library as template. The 111 bp fragment encoding mature LL-37 gene was subcloned into pGAPZ-E, an episomal form of the pGAPZB vector incorporating PARS1. It was then transformed into the P. pastoris X-33 strain for intracellular expression. A small peptide with a molecular mass of about 5 kDa was detected by 17% peptide-PAGE analysis. The recombinant LL-37 peptide was purified from the gel and its amino acid sequence was determined by LC-ESI-MS/MS analysis. The initiating amino acid, methionine, was still attached to the N-terminal region of recombinant LL-37. LL-37 crude extract from P. pastoris showed an antimicrobial activity against Micrococcus luteus as the test strain. The successful expression of human LL-37 indicates that the system may be applicable to the expression of other human defensins without resorting to fusion protein constructions.

Anti-Bacterial Agents↗