Oceanic fronts are widespread mesoscale features that exist in the boundary between different water masses. Despite the recognized importance of bacterioplankton (including bacteria and archaea) on the marine biogeochemical cycles and the ubiquitousness of fronts, the effect of frontal zones on the distribution of bacterioplankton community remains unknown. Using 16S rRNA gene sequencing coupled with a high spatial resolution analysis of the physical properties of the water masses, we demonstrate strong shifts in bacterioplankton community composition (BCC) across the subtropical frontal zone off New Zealand. The transition between water masses resulted in a clear modification of the dominant taxa and a significant increase in community dissimilarity. Our results, linking physical oceanography and marine molecular ecology, support the strong role of oceanic frontal zones in delimiting the distribution of bacterioplankton in the ocean.

No abstract

The recent regulations, which impose limits on single use plastics and packaging, are encouraging the development of bioplastics market. Some bioplastics are labelled as compostable with the organic waste according to a specific certification (EN 13432), however the conditions of industrial composting plants are generally less favourable than the standard test conditions. Aiming at studying the effective degradation of marketable bioplastic products under composting, the current research stresses novel elements which can strongly influence bioplastics degradation: the simulation of industrial composting conditions and the thickness of bioplastic products, ranging between 50 and 500 µm. The research approaches these critical aspects simulating a composting test of 20 days of thermophilic phase followed by 40 days of maturation phase, on starch-based polymer Mater-Bi® (MB), polybutylene adipate terephthalate (PBAT), polylactic acid (PLA) of different thickness. Conventional low density polyethylene (LDPE) was introduced as negative control. An overall study with Fourier Transform InfraRed (FTIR), ThermoGravimetric Analysis (TGA), Gel Permeation Chromatography (GPC), Scanning Electron Microscope (SEM) and visual inspections was applied. Results highlighted that MB film presented the highest degradation rate, 45 ± 4.7% in terms of weight loss. Both MB and PBAT were subjected to physico-chemical features change, while LDPE presented slight degradation signs. The most critical observations have been done for PLA, which is strongly influenced both by thickness and thermophilic phase duration, shorter than the EN 13432 conditions.

The aim of the study was to understand the effect of a long-term metal exposure (110 years) on sediment microbial communities. Two freshwater sites, Férin and MetalEurop, differing by one order of magnitude in metal levels (MetalEurop: 3218 mg Zn kg(-1) ; 913 mg Pb kg(-1) ) were compared by shotgun metaproteogenomics. A total of 69-118 Mpb of DNA and 943-1241 proteins were obtained. PhymmBL analysis of the DNA sequences indicated that the phylogenetic profile was similar in both stations and that β-Proteobacteria were dominant. However, subtle but significant changes were observed for some bacteria: e.g. Pseudomonas (+0.4%), Leptothrix (-0.4%), Thiobacillus (+0.36%) and Acidovorax (+0.48%). Using the stamp software, the two communities were found to be functionally very similar. However, significant genetic differences (10(-6) < P < 10(-3) ) were observed for three SEED categories: synthesis of exopolymeric substances, virulence and defence mechanisms (including czcA metal efflux genes), and elements involved in horizontal gene transfer. The CzcA protein was found by metaproteomics in MetalEurop, but the levels were too low to allow comparisons. It is concluded that bacterial communities in freshwater sediments may adapt to high metal levels without broad changes in the structure of the population.

No abstract