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Galdieria is a photosynthetic unicellular protist, inhabiting thermoacidic environments around the world. The synchronicity of these thermoacidophilic algae with their extreme habitats makes them unable to thrive in different ecological conditions. The genetic structure of Galdieria populations has not yet been studied. In this report, the level of genetic diversity and struc- ture of five Galdieria populations from Iceland were assessed through both random amplified polymorphic DNA (RAPD) markers, and a partial calmodulin gene fragment (previously used to assess the population structure of these extremophilic algae). The level of population differentiation from both the RAPD and CaM markers was estimated using PLP, percentage of polymorphic loci; H, the expected heterozygosity; I, Shannon’s information index, Ks, Kst. The migration ability of the Galdieria populations was suggested by the high level of genetic variations scored within each Galdieria population and by the small number of polymorphisms detected between the different Icelandic populations. The low genetic diversity between the two species was highlighted by RAPD and calmodulin markers, suggesting for the first time an interspecific genetic flow between species as strategy to evolve in stressful environments. Galdieria is a photosynthetic unicellular protist, inhabiting thermoacidic environments around the world. The synchronicity of these thermoacidophilic algae with their extreme habitats makes them unable to thrive in different ecological conditions. The genetic structure of Galdieria populations has not yet been studied. In this report, the level of genetic diversity and structure of five Galdieria populations from Iceland were assessed through both random amplified polymorphic DNA (RAPD) markers, and a partial calmodulin gene fragment (previously used to assess the population structure of these extremophilic algae). The level of population differentiation from both the RAPD and CaM markers was estimated using PLP, percentage of polymorphic loci; H, the expected heterozygosity; I, Shannon’s information index, Ks, Kst. The migration ability of the Galdieria populations was suggested by the high level of genetic variations scored within each Galdieria population and by the small number of polymorphisms detected between the different Icelandic populations. The low genetic diversity between the two species was highlighted by RAPD and calmodulin markers, suggesting for the first time an interspecific genetic flow between species as strategy to evolve in stressful environments.

Background In vitro studies with cell line infection models are beginning to disclose the strategies that Neisseria meningitidis uses to survive and multiply inside the environment of the infected host cell. The goal of this study was to identify novel virulence determinants that are involved in this process using an in vitro infection system. Results By using reverse transcriptase-PCR differential display we have identified a set of meningococcal genes significantly up-regulated during residence of the bacteria in infected HeLa cells including genes involved in L-glutamate transport (gltT operon), citrate metabolism (gltA), disulfide bond formation (dsbC), two-partner secretion (hrpA-hrpB), capsulation (lipA), and DNA replication/repair (priA). The role of PriA, a protein that in Escherichia coli plays a central role in replication restart of collapsed or arrested DNA replication forks, has been investigated. priA inactivation resulted in a number of growth phenotypes that were fully complemented by supplying a functional copy of priA. The priA-defective mutant exhibited reduced viability during late logarithmic growth phase. This defect was more severe when it was incubated under oxygen-limiting conditions using nitrite as terminal electron acceptors in anaerobic respiration. When compared to wild type it was more sensitive to hydrogen peroxide and the nitric oxide generator sodium nitroprusside. The priA-defective strain was not affected in its ability to invade HeLa cells, but, noticeably, exhibited severely impaired intracellular replication and, at variance with wild type and complemented strains, it co-localized with lysosomal associated membrane protein 1. Conclusion In conclusion, our study i.) demonstrates the efficacy of the experimental strategy that we describe for discovering novel virulence determinants of N. meningitidis and ii.) provides evidence for a role of priA in preventing both oxidative and nitrosative injury, and in intracellular meningococcal replication.