Carbon stable isotope record in the coral species Siderastrea stellata: A link to the Suess Effect in the tropical South Atlantic Ocean

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Coral skeletons are natural archives whose geochemical signatures provide insights into the tropical ocean history beyond the instrumental record. Carbon stable isotopes from coral skeletons (δ13Ccoral) have been used as a proxy for multiple variables on a seasonal basis. Long-term changes in coral δ13C could be related to the changing isotopic composition of the dissolved inorganic carbon (δ13CDIC). δ13CDIC in turn reflects changes in the δ13C of atmospheric CO2, which in the modern Earth system is governed primarily by anthropogenic injection of CO2 into the atmosphere – a process known as the Suess Effect. Here we report three δ13C coral-based records of Siderastrea stellata from the tropical South Atlantic. U-series dating for the colonies 12SFB-1, 13SS-1 and 13SS-2 suggests these corals lived 13, 57 and 65 years, respectively. Short-term δ13C variations in their skeletal aragonite are dominated by interannual variation. All three δ13C records additionally exhibit an overall decreasing trend, with a depletion of about −0.0243 ± 0.0057‰·yr−1 (12SFB-1), −0.0208 ± 0.0007‰·yr−1 (13SS-1) and −0.0214 ± 0.0013‰·yr−1 (13SS-2). These rates of the coral records from Rocas Atoll are similar to the reported trend for the δ13C of atmospheric CO2 over the years 1960–1990 (−0.023 to −0.029‰·yr−1), and to the decreasing rates of global δ13CDIC. Our findings suggest that multiple δ13C coral-based records are required for confidently identifying local changes in the δ13CDIC of the ocean. This information, in turn, can be used to infer changes in the δ13C of the atmospheric CO2 composition and provide valuable information about recent changes on the carbon biogeochemical cycle during the Anthropocene epoch.NSP acknowledges the National Counsel of Technological and Scientific Development (CNPq) for a Post-Doctoral Scholarship Proc. no 150405/2015-4. We thank the chief of the Biological Reserve of Rocas Atoll, Maurizélia de Brito Silva and the field team Tiago Albuquerque, Miguel Miranda, Mirella B. Costa and Eduardo Macêdo, for the great assistance in this study. We thank Gilsa Santana, Vilma Sobral (NEG-LABISE, Brazil) and Bo Petersen (University of Copenhagen) for assisting in stable isotope measurements. We are thankful for the critical and constructive comments of the anonymous reviewers. The 2013 field work was partially supported by National Geographic Waitt Foundation grant W21-12 to K.H.K. and R.K.P.K. U-Th dating was supported by grants from Ministry of Science and Technology (MOST) (105-2119-M-002-001, 106-2628-M-002-013 to C.-C.S.) and the National Taiwan University (105R7625 to C.-C.S.). This manuscript is the scientific contribution no 288 of the NEG-LABISE, UFPE, a contribution of the Reef Ecosystems Working Group of the INCT Ambientes Marinhos Tropicais (InctAmbTropic – CNPq #565.054/2010-4) and represents contribution 5470 of the University of Maryland Center for Environmental Science

Type 1 Fimbriae, a Colonization Factor of Uropathogenic Escherichia coli, Are Controlled by the Metabolic Sensor CRP-cAMP

Type 1 fimbriae are a crucial factor for the virulence of uropathogenic Escherichia coli during the first steps of infection by mediating adhesion to epithelial cells. They are also required for the consequent colonization of the tissues and for invasion of the uroepithelium. Here, we studied the role of the specialized signal transduction system CRP-cAMP in the regulation of type 1 fimbriation. Although initially discovered by regulating carbohydrate metabolism, the CRP-cAMP complex controls a major regulatory network in Gram-negative bacteria, including a broad subset of genes spread into different functional categories of the cell. Our results indicate that CRP-cAMP plays a dual role in type 1 fimbriation, affecting both the phase variation process and fimA promoter activity, with an overall repressive outcome on fimbriation. The dissection of the regulatory pathway let us conclude that CRP-cAMP negatively affects FimB-mediated recombination by an indirect mechanism that requires DNA gyrase activity. Moreover, the underlying studies revealed that CRP-cAMP controls the expression of another global regulator in Gram-negative bacteria, the leucine-responsive protein Lrp. CRP-cAMP-mediated repression is limiting the switch from the non-fimbriated to the fimbriated state. Consistently, a drop in the intracellular concentration of cAMP due to altered physiological conditions (e.g. growth in presence of glucose) increases the percentage of fimbriated cells in the bacterial population. We also provide evidence that the repression of type 1 fimbriae by CRP-cAMP occurs during fast growth conditions (logarithmic phase) and is alleviated during slow growth (stationary phase), which is consistent with an involvement of type 1 fimbriae in the adaptation to stress conditions by promoting biofilm growth or entry into host cells. Our work suggests that the metabolic sensor CRP-cAMP plays a role in coupling the expression of type 1 fimbriae to environmental conditions, thereby also affecting subsequent attachment and colonization of host tissues

Metaproteogenomic analysis of a community of sponge symbionts

Sponges harbour complex communities of diverse microorganisms, which have been postulated to form intimate symbiotic relationships with their host. Here we unravel some of these interactions by characterising the functional features of the microbial community of the sponge Cymbastela concentrica through a combined metagenomic and metaproteomic approach. We discover the expression of specific transport functions for typical sponge metabolites (for example, halogenated aromatics, dipeptides), which indicates metabolic interactions between the community and the host. We also uncover the simultaneous performance of aerobic nitrification and anaerobic denitrification, which would aid to remove ammonium secreted by the sponge. Our analysis also highlights the requirement for the microbial community to respond to variable environmental conditions and hence express an array of stress protection proteins. Molecular interactions between symbionts and their host might also be mediated by a set of expressed eukaryotic-like proteins and cell-cell mediators. Finally, some sponge-associated bacteria (for example, a Phyllobacteriaceae phylotype) appear to undergo an evolutionary adaptation process to the sponge environment as evidenced by active mobile genetic elements. Our data clearly show that a combined metaproteogenomic approach can provide novel information on the activities, physiology and interactions of sponge-associated microbial communities. © 2012 International Society for Microbial Ecology All rights reserved