Participation of the arcRACME protein in self-activation of the arc operon located in the arginine catabolism mobile element in pandemic clone USA300

ABSTRACT Staphylococcus aureus pandemic clone USA300 has, in addition to its constitutive arginine catabolism (arc) gene cluster, an arginine catabolism mobile element (ACME) carrying another such cluster, which gives this clone advantages in colonisation and infection. Gene arcR, which encodes an oxygen-sensitive transcriptional regulator, is inside ACME and downstream of the constitutive arc gene cluster, and this situation may have an impact on its activation. Different relative expression behaviours are proven here for arcRACME and the arcACME operon compared to the constitutive ones. We also show that the artificially expressed recombinant ArcRACME protein binds to the promoter region of the arcACME operon; this mechanism can be related to a positive feedback model, which may be responsible for increased anaerobic survival of the USA300 clone during infection-related processes.

Correlations between major risk factors and closely related Mycobacterium tuberculosis isolates grouped by three current enotyping procedures: a population-based study in northeast Mexico

The characteristics of tuberculosis (TB) patients related to a chain of recent TB transmissions were investigated. Mycobacterium tuberculosis (MTB) isolates (120) were genotyped using the restriction fragment length polymorphism-IS6110 (R), spacer oligotyping (S) and mycobacterial interspersed repetitive units-variable number of tandem repeats (M) methods. The MTB isolates were clustered and the clusters were grouped according to the similarities of their genotypes. Spearman’s rank correlation coefficients between the groups of MTB isolates with similar genotypes and those patient characteristics indicating a risk for a pulmonary TB (PTB) chain transmission were ana- lysed. The isolates showing similar genotypes were distributed as follows: SMR (5%), SM (12.5%), SR (1.67%), MR (0%), S (46.67%), M (5%) and R (0%). The remaining 35 cases were orphans. SMR exhibited a significant correlation (p < 0.05) with visits to clinics, municipalities and comorbidities (primarily diabetes mellitus). S correlated with drug consumption and M with comorbidities. SMR is needed to identify a social network in metropolitan areas for PTB transmission and S and M are able to detect risk factors as secondary components of a transmission chain of TB.

Mycobacterial Interspersed Repetitive Unit typing in Mycobacterium tuberculosis isolates from Sichuan Province in China.

Background & objectives: Emergence and spread of drug resistant Mycobacterium tuberculosis is a serious threat to tuberculosis (TB) control programme. Therefore, the objective of this study was to genotype drug-resistant M. tuberculosis strains isolated from patients in Sichuan, China, using Mycobacterial Interspersed Repetitive Units (MIRU) for epidemiological analysis. Methods: Drug-resistance testing of M. tuberculosis isolates from pulmonary TB patients was confirmed by proportion method. Twelve MIRU loci were analyzed on 80 drug-resistant and 9 susceptible isolates by polymerase chain reaction and agarose gel electrophoresis. Hunter-Gaston discriminatory index (HGI) values were determined for each 12 MIRU loci for the evaluation of their discrimination power. Results: Among 12 MIRU loci examined, polymorphic bands could be generated on 11 loci. Sixty five isolates had distinct MIRU patterns, while other 24 belonged to 8 clusters and resistant to at least one anti-TB drug tested. The association between the MIRU patterns and the mutation patterns of drug-resistance relevant target genes was not significant among the drug-resistant isolates. Interpretation & conclusions: The results showed that with a satisfactory discrimination power exhibited, the 12 loci based MIRU typing could be a valuable tool for epidemiological studies in M. tuberculosis isolates from Sichuan.

Exploring the Antarctic soil metagenome as a source of novel cold-adapted enzymes and genetic mobile elements / Explorando el metagenoma del suelo antártico como fuente de nuevas enzimas adaptadas al frío y elementos génicos móviles

Metagenomic library PP1 was obtained from Antarctic soil samples. Both functional and genotypic metagenomic screening were used for the isolation of novel cold-adapted enzymes with potential applications, and for the detection of genetic elements associated with gene mobilization, respectively. Fourteen lipase/esterase-, 14 amylase-, 3 protease-, and 11 cellulase-producing clones were detected by activity-driven screening, with apparent maximum activities around 35 °C for both amylolytic and lipolytic enzymes, and 35-55 °C for cellulases, as observed for other cold-adapted enzymes. However, the behavior of at least one of the studied cellulases is more compatible to that observed for mesophilic enzymes. These enzymes are usually still active at temperatures above 60 °C, probably resulting in a psychrotolerant behavior in Antarctic soils. Metagenomics allows to access novel genes encoding for enzymatic and biophysic properties from almost every environment with potential benefits for biotechnological and industrial applications. Only intI- and tnp-like genes were detected by PCR, encoding for proteins with 58-86 %, and 58-73 % amino acid identity with known entries, respectively. Two clones, BAC 27A-9 and BAC 14A-5, seem to present unique syntenic organizations, suggesting the occurrence of gene rearrangements that were probably due to evolutionary divergences within the genus or facilitated by the association with transposable elements. The evidence for genetic elements related to recruitment and mobilization of genes (transposons/integrons) in an extreme environment like Antarctica reinforces the hypothesis of the origin of some of the genes disseminated by mobile elements among "human-associated" microorganisms.

A partir de muestras de suelo antártico se obtuvo la metagenoteca PP1. Esta fue sometida a análisis funcionales y genotípicos para el aislamiento de nuevas enzimas adaptadas al frío con potenciales aplicaciones, y para la detección de elementos génicos asociados a la movilización de genes, respectivamente. Por tamizaje fenotípico se detectaron 14, 14, 3 y 11 clones productores de lipasas/esterasas, proteasas, amilasas y celulasas, respectivamente, con actividades máximas aparentes de 35 °C para las amilasas y lipasas, y de 35-55 °C para las celulasas, tal como se observó para otras enzimas adaptadas al frío. Sin embargo, una celulasa parece ser compatible con enzimas mesófilas, las que usualmente se mantienen activas hasta por sobre 60 °C. Este hecho probablemente esté asociado a un comportamiento psicrotolerante en los suelos antárticos. La metagenómica permite acceder a una nueva miríada de productos metabólicos con potenciales beneficios para aplicaciones biotecnológicas e industriales. Se detectaron los genes tipo intI y tnp por PCR, y sus productos génicos deducidos tuvieron identidades del 58 al 86 % y del 58 al 73 % con secuencias conocidas, respectivamente. Dos clones, BAC 27A-9 y BAC 14A-5, parecen presentar organizaciones sintéticas únicas, lo cual sugiere la existencia de rearreglos génicos probablemente debidos a divergencias evolutivas dentro del género o facilitados por la asociación de elementos de transposición. La evidencia de elementos génicos relacionados con el reclutamiento y la movilización de genes en ambientes extremos como la Antártida refuerza la hipótesis sobre el origen de algunos genes diseminados por elementos móviles entre los microorganismos asociados al ser humano.