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Genetic transformation of the epidemic typhus-causing intracellular pathogen Ricketssia prowazekii was effected by electroporation. The target gene was rpoB encoding the beta subunit of RNA polymerase. The mutant gene inserted in the transformed Rickettsia was the rifampin-resistant RNA polymerase gene. Transformation was effected through homologous recombination. This is the first report of a genetic system in R. prowazekii.

Research has been conducted on the etiologic agent of epidemic typhus Rickettsia prowazekii. The expression of Escherichia coli ereB gene in this parasitic bacterium has been performed.

Recent studies suggested that the accumulation of muscular free fatty acids (FFA) might be responsible for the mitochondrial dysfunction and insulin resistance (IR) seen in type 2 diabetes mellitus (T2DM), and that the type of FFA is critical in this process. Additionally oxidative stress, which results from increased production of reactive oxygen/nitrogen species (ROS/RNS) leads to 1R and T2DM. We hypothesized that oxidative damage to mitochondrial DNA (mtDNA) is an early step involved in mitochondrial dysfunction and IR following exposure of skeletal muscle to FFA. Damage to mtDNA initiates processes which heighten production of ROS causing progressive mitochondrial and cellular dysfunction which ultimately leads to IR. To test this hypothesis, rat L6 myotubes were exposed to palmitate, which is the most prevalent saturated FFA; oleate, which makes up 80% of the circulating monounsaturated pool; and a mixture (oleate/palmitate; 2/1 ). Previously palmitate has been shown to induce IR in L6 myotubes whereas oleate improves insulin sensitivity. Moreover, palmitate-induced IR and apoptosis were positively related, while oleate did not induce apoptosis in L6 myotubes. The current studies were undertaken to investigate whether FFA-induced apoptosis and IR correlate with mtDNA damage and mitochondrial dysfunction in L6 myotubes. The results showed that only palmitate caused production of nitric oxide (NO), ROS, mtDNA damage and apoptosis in L6 myotubes. Incubation of L6 myotubes with similar concentrations of either oleate alone or oleate combined with palmitate did not stimulate production of NO. Oleate did not cause mtDNA damage in L6 myotubes and the addition of oleate to palmitate prevented palmitate-induced mtDNA damage, and palmitate-induced decrease in total ATP levels and cell viability. Addition of oleate to palmitate prevented palmitate-induced apoptosis. CONCLUSION: FFA-induced mtDNA damage is a key component contributing to IR in skeletal muscle probably by triggering mitochondrial dysfunction which leads to apoptosis. [ABSTRACT FROM AUTHOR]

Insulin resistance plays a key role in the development of type 2 diabetes mellitus and is also associated with several other diseases, such as obesity, hypertension, and cardiovascular diseases. Type 2 diabetes and obesity have become epidemic worldwide in the past few decades, and epidemiological and metabolic evidence indicates that the two conditions are linked closely through insulin resistance. The perturbation of free fatty acid (FFA) metabolism is now accepted to be a major factor contributing to whole-body insulin resistance, including that in skeletal muscle. Acute exposure to FFAs and excess dietary lipid intake are strongly associated with the pathogenesis of muscle insulin resistance. Despite an enormous amount of published research and the proposal of numerous hypotheses, however, the mechanisms underlying FFA-induced skeletal muscle insulin resistance have not been fully elucidated. This chapter describes existing hypotheses, recent findings, and debates about the role of FFAs in the development of muscle insulin resistance. Therapeutic options for this condition are also discussed., (© 2014 Elsevier Inc. All rights reserved.)