Unraveling the multifaceted resilience of arsenic resistant bacterium Deinococcus indicus.

Arsenic (As) is a toxic heavy metal widely found in the environment that severely undermines the integrity of water resources. Bioremediation of toxic compounds is an appellative sustainable technology with a balanced cost-effective setup. To pave the way for the potential use of Deinococcus indicus, an arsenic resistant bacterium, as a platform for arsenic bioremediation, an extensive characterization of its resistance to cellular insults is paramount. A comparative analysis of D. indicus cells grown in two rich nutrient media conditions (M53 and TGY) revealed distinct resistance patterns when cells are subjected to stress via UV-C and methyl viologen (MV). Cells grown in M53 demonstrated higher resistance to both UV-C and MV. Moreover, cells grow to higher density upon exposure to 25 mM As(V) in M53 in comparison with TGY. This analysis is pivotal for the culture of microbial species in batch culture bioreactors for bioremediation purposes. We also demonstrate for the first time the presence of polyphosphate granules in D. indicus which are also found in a few Deinococcus species. To extend our analysis, we also characterized DiArsC2 (arsenate reductase) involved in arsenic detoxification and structurally determined different states, revealing the structural evidence for a catalytic cysteine triple redox system. These results contribute for our understanding into the D. indicus resistance mechanism against stress conditions.

A possible Echinococcus granulosus calcified cyst found in a medieval adult female from the churchyard of Santo Domingo de Silos (Prádena del Rincón, Madrid, Spain).

Calcification, or mineralisation, can occur as part of a natural process, or by pathological processes. The purpose of this work is to examine an unidentified semi-spherical and perforate hollow mass, found near the pelvis of an adult female, dated 12th-13th century AD, exhumed of the Church of Santo Domingo de Silos (Prádena del Ricón, Madrid, Spain). The mass was examined by SEM and Energy Dispersive X-Ray Spectroscopy. These procedures revealed a heterogeneous inner surface with both smooth and irregular areas. A larger spherical and several smaller crescent-shaped perforations were noticed. X-ray microanalysis revealed the presence of the elements C, K, P, Ca, Al, Si, Fe, and Mg. The co-localisation of Ca and P suggests that they may be combined in a mineral matrix, likely formed in vivo. Other minerals probably came from the soil, although Fe could be related to the presence of blood. The macroscopic and microscopic appearances, chemical composition, and location of the calcified mass point to a possible hydatid cyst from Echinococcus granulosus, common in agricultural populations. This study used a suite of analytical techniques that are useful in the diagnosis of unknown calcified masses and can, therefore, be recommended for use in future analytical work.