SsrA and SmpB are known to play important roles in translational quality control and are essential for virulence in many human and animal pathogenic bacteria. The physiological roles and contribution of SsrA and SmpB to plant pathogen are unclear. Here, we present evidence to show that ssrA and smpB are involved in pathogenesis of Xanthomonas campestris pathovar campestris, the cause of black rot diseases in crucifers. The ssrA and smpB mutants exhibited defects in bacterial attachment, cell motility, and extracellular enzyme activity. The mutation of ssrA and smpB also resulted in a reduction in temperature tolerance. These altered phenotypes of the ssrA and smpB mutants could be complemented to wild-type levels by the intact ssrA and smpB genes. This is the first demonstration of the roles of SsrA and SmpB in phytopathogen.

Antimicrobial resistance (AMR) has become a serious global health threat. Education could play a decisive role, so the scope of innovative educational projects, such as MicroMundo, should be analysed. MicroMundo is a service-learning project for the exploration of microbial biodiversity in soils in search of new antibiotics. In order to evaluate the contribution of MicroMundo to the improvement of knowledge about AMR as well as the optimal age of the participants, an open questionnaire before and after the educational intervention (for secondary school students) and a satisfaction survey (for all participants) were carried out. Program instruction began in university and continued through secondary school; 14 teachers (phase 1) and 137 students from three educational levels (phase 2) participated. MicroMundo was successfully implemented, showing a statistically significant improvement in knowledge about antibiotics, resistance, health and environmental consequences, and possible measures to reverse the problem, at all educational levels. Furthermore, the satisfaction surveys revealed a growing interest in research and science. Therefore, students of general branches, who have not yet opted for a scientific line, would be the most suitable to conduct the program. In conclusion, MicroMundo is recommended as a training method to raise awareness about AMR and promote scientific vocations.

Polyphosphate kinase 1 (Ppk1) generates polyphosphates (polyPs) by catalyzing phosphate transfer from ATP. In the presence of ATP, Myxococcus xanthus Ppk1 showed the highest activity with polyP60-70 but also showed high activity with orthophosphate and pyrophosphate. Ppk1 synthesizes long-chain polyPs with more than 1 000 phosphate residues from orthophosphate or pyrophosphate present in high concentrations, suggesting that in M. xanthus, Ppk1 uses intracellular ortho/pyrophosphate as an initial primer for polyP production. During M. xanthus starvation-induced development, the specific activity of Ppk1 peaked at 12 h (300-800 nmol/min/mg) and then gradually decreased. The polyP concentration was highest during mound formation (45 nmol phosphate/mg protein); then, the level of long-chain polyPs decreased and that of short-chain polyPs increased during fruiting body and spore formation. M. xanthus expresses two exopolyphosphatases, Ppx1 and Ppx2, which mainly degrade short- and long-chain polyPs, respectively, both of which were highest in vegetative cells and were detected during starvation, which may account for the degradation of polyPs. Thus, polyPs synthesized by Ppk1 early in starvation-induced development could be degraded by exopolyphosphatases and may also be used as substrates by polyP:AMP phosphotransferases and polyphosphate/ATP-NAD kinases to generate ADP and NADP+, respectively.

N-Acyl homoserine lactones (N-HLs) are signaling molecules used by Gram-negative bacteria in a phenomenon called quorum sensing (QS). Bacteria will detect N-HLs as a way of monitoring their population which, upon reaching a critical level, will express a specific phenotype. An example is the expression of bioluminescence by Vibrio fischeri. A limited number of studies have considered the chirality of these molecules nor used highly sensitive detection methods. Here, the production of D,L-N-HLs are monitored for V. fischeri, B. cepacia, P. fluorescens and P. putida, using highly sensitive tandem mass spectrometry analysis. Novel N-HLs are reported for both V. fischeri and B. cepacia including a plethora of previously unknown D-N-HLs, including the first D-N-HLs containing oxo and hydroxy functionalities. Anomalously, N-HLs were not detected in any cultures of P. fluorescens and P. putida, which are species that previously were reported to produce N-HLs. However, it is apparent that differences in the reported occurrence and levels of N-HLs can result from: different strains of bacteria, b) different growth media and environmental conditions and c) sometimes false positive results from detection methodologies. Time studies of V. fischeri suggest the possibility that separate synthetic and elimination pathways exist between D- and L-N-HLs. Possible biological processes that could be the source of D-N-HL production are considered.