Microbial shifts associated to ENSO-derived thermal anomalies reveal coral acclimation at holobiont level.

The coral microbiome conforms a proxy to study effects of changing environmental conditions. However, scarce information exists regarding microbiome dynamics and host acclimation in response to environmental changes associated to global-scale disturbances. We assessed El Niño Southern Oscillation (ENSO)-derived thermal anomalies shifts in the bacterial microbiome of Pacifigorgia cairnsi (Gorgoniidae: Octocorallia) from the remote island of Malpelo in the Tropical Eastern Pacific. Malpelo is a hot spot of biodiversity and lacks direct coastal anthropogenic impacts. We evaluated the community composition and predicted functional profiles of the microbiome during 2015, 2017 and 2018, including different phases of ENSO cycle. The bacterial community diversity and composition between the warming and cooling phase were similar, but differed from the neutral phase. Relative abundances of different microbiome core members such as Endozoicomonas and Mycoplasma mainly drove these differences. An acclimated coral holobiont is suggested not just to warm but also to cold stress by embracing similar microbiome shifts and functional redundancy that allow maintaining coral's viability under thermal stress. Responses of the microbiome of unperturbed sea fans such as P. cairnsi in Malpelo could be acting as an extended phenotype facilitating the acclimation at the holobiont level.

Isolation and Potential Biocementation of Calcite Precipitation Inducing Bacteria from Colombian Buildings.

Microbiological induced calcium carbonate or calcite precipitation (MICP) has become a highly researched issue due to its multiple applications in the construction industry, being a promising alternative with a great biotechnological importance. In this work, potential calcite precipitation inducing bacteria were isolated from mortar and concrete samples of different buildings at the National University of Colombia. Eighteen crystal-precipitating strains were recovered in Urea-CaCl2 solid medium. The 16S rRNA gene sequencing identified isolates as Arthrobacter, Psychrobacillus and Rhodococcus genera. It is reported, for the first time, the calcite precipitation by P. psycrodurans and R. qingshengii. Optical microscopy and Scanning Electron Microscopy showed crystals with irregular and spherical shapes, and beige and white colours. Furthermore, crystals formation appeared to be strain-specific. X-Ray diffraction analysis confirmed crystals composition as CaCO3. Biocementation tests showed that MICP treatments of mortar cubes using P. psycrodurans caused an increase in their compressive strength compared to control samples. The positive action of a native MICP strain in mortar blocks biomineralization is shown, which is of great interest and potential for the construction industry.