Planetary protection – Approaching uncultivable microorganisms

With ESA's MiDiv project [Rettberg, P., Fritze, D., Verbarg, S., Nellen, J., Horneck, G., Stackebrandt, E., Kminek, G. Final report ESA project MiDiv, ESA contract number 17538/03/NL/VS] the exobiology group at the German Aerospace Centre (DLR) in Cologne started to investigate the microbial diversity found on spacecrafts and in assembly halls used by Europe [Rettberg, P., Nellen, J., Horneck, G., Fritze, D., Verbarg, S., Stackebrandt, E., Kminek, G. Determination of the microbial diversity of spacecraft assembly facilities: first results of the ESA project MiDiv. Adv. Space Res., 2005]. So far this examination was limited to cultivable microorganisms, probably excluding the majority of organisms present. To approach the microbial diversity of uncultivable microorganisms, new methods, have to be implemented into the analysing process. Therefore, we describe in this paper the adaptation of an existing protocol (surface sampling with swabs) to be used with a method based on the detection of DNA-fragments by polymerase chain reaction (PCR). Our data indicate that it is feasible to adapt the standardized sample taking process to be used with the PCR-method. While using a classical swabbing/cultivation approach for the detection of microorganisms on a surface, two impairing factors have to be accounted for. First, not all bacteria present on a surface will be taken up by the swab and second, not all the bacteria taken up will be released again from the swab. This will lead to a diminished overall estimation of the microorganisms present on a surface. Our studies further suggested that the estimated data had to be corrected by a factor of 2–3 to correspond with the actual numbers of spores spotted

Investigation of the halophilic PET hydrolase PET6 from Vibrio gazogenes

The handling of plastic waste and the associated ubiquitous occurrence of microplastic poses one of the biggest challenges of our time. Recent investigations of plastic degrading enzymes have opened new prospects for biological microplastic decomposition as well as recycling applications. For polyethylene terephthalate, in particular, several natural and engineered enzymes are known to have such promising properties. From a previous study that identified new PETase candidates by homology search, we chose the candidate PET6 from the globally distributed, halophilic organism Vibrio gazogenes for further investigation. By mapping the occurrence of Vibrios containing PET6 homologs we demonstrated their ubiquitous prevalence in the pangenome of several Vibrio strains. The biochemical characterization of PET6 showed that PET6 has a comparatively lower activity than other enzymes but also revealed a superior turnover at very high salt concentrations. The crystal structure of PET6 provides structural insights into this adaptation to saline environments. By grafting only a few beneficial mutations from other PET degrading enzymes onto PET6, we increased the activity up to three fold, demonstrating the evolutionary potential of the enzyme. MD simulations of the variant helped rationalize the mutational effects of those mutants and elucidate the interaction of the enzyme with a PET substrate. With tremendous amounts of plastic waste in the Ocean and the prevalence of Vibrio gazogenes in marine biofilms and estuarine marshes, our findings suggest that Vibrio and the PET6 enzyme are worthy subjects to study the PET degradation in marine environment

Evidence of autoinducer-dependent and autoinducer-independent heterogeneous gene expression in <em>Sinorhizobium fredii </em>NGR234.

Populations of genetically identical Sinorhizobium fredii NGR234 cells differ significantly in their expression profiles of autoinducer (AI)-dependent and AI-independent genes. Promoter fusions of the NGR234 AI synthase genes traI and ngrI showed high levels of phenotypic heterogeneity during growth in TY medium on a single cell level. However, adding very high concentrations of N-(3-oxooctanoyl-)-L-homoserine lactone resulted in a more homogeneous expression profile. Similarly, the lack of internally synthesized AIs in the background of the NGR234-&Delta;traI or the NGR234-&Delta;ngrI mutant resulted in a highly homogenous expression of the corresponding promoter fusions in the population. Expression studies with reporter fusions of the promoter regions of the quorum quenching genes dlhR, qsdR1 and the pNGR234b encoded type IV pilus gene cluster suggested that other factors than AI molecules may affect NGR234 phenotypic heterogeneity. Further studies with root exudates and developing Arabidopsis thaliana seedlings provide first evidence that plant root exudates have strong impact on the heterogeneity of AI synthase and quorum quenching genes in NGR234. Thereby, plant-released octopine appears to play a key role in modulation of heterogeneous gene expression

Towards a History of Mass Violence in the Etat Indépendant du Congo, 1885-1908

The present article provides an up-to-date scholarly introduction to mass violence in the Etat Indépendant du Congo (Congo Free State, EIC). Its aims are twofold: to offer a point of access to the extensive literature and historical debates on the subject, and to make the case for exchanging the currently prevalent top-down narrative, with its excessive focus on King Leopold's character and motives, for one which considers the EIC's culture of violence as a multicausal, broadly based and deeply engrained social phenomenon. The argument is divided into five sections. Following a general outline of the EIC's violent system of administration, I discuss its social and demographic impact (and the controversy which surrounds it) to bring out the need for more regionally focused and context sensitive studies. The dispute surrounding demographics demonstrates that what is fundamentally at stake is the place the EIC's extreme violence should occupy in the history of European ‘modernity’. Since approaches which hinge on Leopoldian exceptionalism are particularly unhelpful in clarifying this issue, I pause to reflect on how such approaches came to dominate the distinct historiographical traditions which emerged in Belgium and abroad before moving on to a more detailed exploration of a selection of causes underlying the EIC's violent nature. While state actors remain in the limelight, I shift the focus from the state as a singular, normative agent, towards the existence of an extremely violent society in which various individuals and social groups within and outside of the state apparatus committed violent acts for multiple reasons. As this argument is pitched at a high level of abstraction, I conclude with a discussion of available source material with which it can be further refined and updated

Estimativa da concentração espermática do sêmen de peixe pelo método de espermatócrito Sperm concentration estimate of fish semen using spermatocrit method

Um experimento foi realizado com o objetivo de estimar a concentração espermática das espécies dourado (Salminus brasiliensis), curimba (Prochilodus lineatus), jundiá (Rhamdia quelen), cascudo-preto (Rhinelepis aspera) e tilápia-do-nilo (Oreochromis niloticus) pelo método de espermatócrito. Utilizaram-se 19, 58, 51, 43 e 85 reprodutores de dourado, curimba, jundiá, cascudo-preto e tilápia-do-nilo, respectivamente. Com exceção da tilápia-do-nilo, os reprodutores foram submetidos ao processo de indução hormonal e posteriormente submetidos a coleta de sêmen. Foram comparadas as técnicas de mensuração da concentração espermática do sêmen por contagem em câmara hematimétrica de Neubauer e por espermatócrito. Os resultados obtidos foram submetidos à análise de regressão a 5% de probabilidade. As concentrações espermáticas mensuradas por ambas as técnicas apresentaram relação linear, para curimbas, jundiás e tilápias-do-nilo, com equações y = 6,6624 × 10(9) + 3,68553 × 10(8)x; y = 2,153 × 10(9) + 4,426 × 10(8)x e y = -9,0897 × 10(8) + 6,0167 × 10(8), respectivamente. O método de espermatócrito pode ser utilizado para estimar a concentração espermática do sêmen de curimbas, jundiás e tilápias-do-nilo.<br>The objective of this experiment was estimate sperm concentration of "dourado" (Salminus brasiliensis), "curimba" (Prochilodus lineatus), "jundiá" (Rhamdia quelen), "cascudo-preto" (Rhinelepis aspera) and Nile tilapia (Oreochromis niloticus) by the method of spermatocrit. It was used 19, 58, 51, 43 and 85 brood fish of "dourado", "curimba", "jundia", "cascudo-preto" and Nile tilapia, respectively. Except for the Nile tilapia, the fishes were subjected to the hormonal induction process and then submitted to the semen collection. The measurement techniques of the sperm concentration by sperm count in Neubauer chamber (CSPZ) and by spermatocrit (ESPMT) were compared. The results were submitted to the regression analysis at 5% of probability. It was observed that the variables CSPZ and ESPMT presented linear relationship to the "curimba", "jundia" and Nile tilapia with equations y = 6.6624 × 10(9) + 368553 × 10(8)x; y = 2.153 × 10(9) + 4.426 × 10(8)x and y = -9.0897 × 10(8) + 6.0167 × 10(8), respectively. The method of spermatocrit can be used to estimate the sperm concentration of "curimba", "jundiá" and Nile tilapia