An almost complete gene sequence of 165 rDNA of 'Nocardia salmonicida' strain JCM 4826T was determined following cloning and sequencing of the amplified gene. The sequence was aligned with those available for nocardiae and phylogenetic trees inferred using four tree-making algorithms. The organism and the type strain of Nocardia asteroides consistently formed a monophyletic clade with a distant sequence similarity of 97 O/ O. However, previous DNA relatedness experiments showed that strain JCM 4826l and Nocardia asteroides ATCC 19247T belong to different genomic species. The organism was also distinguished from representatives of all validly described species of Nocardia using a combination of phenotypic features. The polyphasic evidence showed that the strain merits recognition as a new species of the genus Nocardia. The name proposed for the new species is Nocardia salmonicida nom. rev.

Aims: To study the relationship between changes in the composition of the outer membrane proteins and the survival of Salmonella typhimurium LT2 in filtered autoclaved seawater containing Toluidine Blue (TB) dye as a photosensitizer. Methods and Results: In samples exposed to TB and excited by artificial visible light, the total viable (TVC) and respiring cell counts (RCC) showed that, although the TVC declined to an undetectable level in 6·5 h, the RCC showed that some cells were still capable of respiration. The porin protein composition changed gradually with OmpC and OmpF becoming undetectable by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis after 8 h of incubation. Hydrogen peroxide‐pretreated cells survived longer compared with the control. Conclusions: Oxidative pretreatment of Salm. typhimurium protects cells from some of the effects of sunlight in the presence of photosensitizers. The changes in porin proteins may play a role in this protection. Significance and Impact of the Study: The study shows that the survival of bacteria under conditions of stress is the result of a linked series of reactions.

-Streptomyces sp. F6616 was found to produce higher levels of extracellular peroxidase activity (0.535 U/ mL) without any inducers than other actinobacteria which are previously reported. Maximum specific peroxidase activity (6.21 U/mg of protein) was obtained after 72 h of incubation at 30 °C in a minimal salt medium (pH 8.0) containing (in wt/v) 0.6% yeast extract and 0.8% ball-milled wheat straw corresponding to a C:N ratio of 4.6:1. Characterization of the peroxidase revealed that the optimal temperature for the enzyme activity, using the standard 2,4-dichlorophenol (2,4-DCP) assay was 50 °C, when the enzyme reaction was performed at pH 8.0. A study of the effect of temperature on the stability of peroxidase over time, showed that the enzyme was stable at 50 °C, with a half-life of 145 min, while at higher temperature the stability and activity was reduced such that at 60 °C the half-life of the enzyme was 30 min. The optimum pH for the activity of the enzyme occurred between pH 9.0 and 10.0. The apparent K m and V max values for the peroxidase preparations were determined to be 1.52 mmol/L and 1.84 U/mg protein, respectively using 2,4-DCP as a substrate. Characterization of the peroxidase activity revealed activity against 2,4-DCP, L-3,4-dihydroxyphenylalanine (L-DOPA), 2,4,5-trichlorophenol and other chlorophenols in the presence of hydrogen peroxide. However, inhibition of peroxidase activity with the addition of potassium cyanide and sodium azide, suggested the presence of heme component in the tertiary structure of the enzyme.

No abstract

The aim of this study was to investigate the impact on numbers of using different media for the enumeration of Escherichia coli subjected to stress, and to evaluate the use of different resuscitation methods on bacterial numbers. E. coli was subjected to heat stress by exposure to 55 degrees C for 1h or to light-induced oxidative stress by exposure to artificial light for up to 8h in the presence of methylene blue. In both cases, the bacterial counts on selective media were below the limits of detection whereas on non-selective media colonies were still produced. After resuscitation in non-selective media, using a multi-well MPN resuscitation method or resuscitation on membrane filters, the bacterial counts on selective media matched those on non-selective media. Heat and light stress can affect the ability of E. coli to grow on selective media essential for the enumeration as indicator bacteria. A resuscitation method is essential for the recovery of these stressed bacteria in order to avoid underestimation of indicator bacteria numbers in water. There was no difference in resuscitation efficiency using the membrane filter and multi-well MPN methods. This study emphasises the need to use a resuscitation method if the numbers of indicator bacteria in water samples are not to be underestimated. False-negative results in the analysis of drinking water or natural bathing waters could have profound health effects.

No abstract

Nocardia are aerobic, catalase-positive, Gram-positive microorganisms and typically acid-alcohol fast at some stage of the growth cycle. The genus Nocardia, a member of Mycolata group, is clinically important because it is an opportunistic pathogen. The sulfonamide derivative medicines are prefered to cure infection caused by Nocardia, such as nocardiaosis and mycetoma. Antimicrobial activities of seven sulfonamide derivatives have been investigated against some Nocardia species and isolates using the disk diffusion method on Sensitest agar medium (Oxoid). Thirty-six organisms, which consisted of 10 soil isolates selected from different clusters of Aymen study (2003), six clinical isolates provided by Ege University, Medical School, Microbiology and Clinical Microbiology Department, four reference strains, 15 type strains and a control strain of Staphylococcus aureus ATCC 43300 were tested. The strongest inhibition was observed in the cases of IV [N-(2-hydroxy-4-nitro-phenyl)-4-methyl-benzensulfonamid], V [N-(2-hydroxy-5-nitro-phenyl)-4-methyl-benzensulfonamid] and III [N-(2-Hydroxy-phenyl)-4-methyl-benzenesulfonamide] against Nocardia. Introducing a hydroxyl group into the ortho position on the ring increased the antimicrobial activity. Substitution of the electron withdrawing groups such as a nitro group increased the antimicrobial activity remarkably.

Taxonomic relationships within the genus Streptomyces have been clarified and extended by the application of genotypic and phenotypic methods to representatives of species with validly published names and putatively novel species (Goodfellow et al., 1992; Manfio et al., 1995;Anderson & Wellington, 2001;Kumar & Goodfellow, 2008 The S. violaceusniger clade currently encompasses species with validly published names and that are mainly circumscribed using a combination of DNA-DNA relatedness and phenotypic data (Labeda & Lyons, 1991;Sembiring et al., 2000;Goodfellow et al., 2007;Kumar & Goodfellow, 2008). Members of the clade have been isolated from geographically diverse soils (Al-Tai et al., 1999;Saintpierre et al., 2003;Hayakawa et al., 2004) and from rhizosphere and non-rhizosphere soils . PCR amplification of DNA extracted from marine and terrestrial samples using S. violaceusniger cladespecific primers has provided evidence for the widespread distribution of novel members of the clade in natural habitats .In the course of a screening programme designed to recover novel streptomycetes from rhizosphere soil, a strain, designated M1463 T , was shown to have activity against several microbial targets and to have colonial and morphological features suggesting that it may be a member of the S. violaceusniger clade. The aim of the present study was to determine the taxonomic status of the isolate using a polyphasic taxonomic approach. The resultant data indicate that the organism should be classified as a representative of a novel species of the genus Streptomyces. Strain M1463T was isolated after 14 days of incubation at 28 u C from the rhizosphere of Robinia pseudoacacia by plating soil suspensions onto starch-casein agar (Küster,The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of Streptomyces samsunensis M1463T is EU077190.