New Biocalcifying Marine Bacterial Strains Isolated from Calcareous Deposits and Immediate Surroundings

Abstract

Marine bacterial biomineralisation by CaCO3 precipitation provides natural limestone structures, like beachrocks and stromatolites. Calcareous deposits can also be abiotically formed in seawater at the surface of steel grids under cathodic polarisation. In this work, we showed that this mineral-rich alkaline environment harbours bacteria belonging to different genera able to induce CaCO3 precipitation. We previously isolated 14 biocalcifying marine bacteria from electrochemically formed calcareous deposits and their immediate environment. By microscopy and µ-Raman spectroscopy, these bacterial strains were shown to produce calcite-type CaCO3. Identification by 16S rDNA sequencing provided between 98.5 and 100% identity with genera Pseudoalteromonas, Pseudidiomarina, Epibacterium, Virgibacillus, Planococcus, and Bhargavaea. All 14 strains produced carbonic anhydrase, and six were urease positive. Both proteins are major enzymes involved in the biocalcification process. However, this does not preclude that one or more other metabolisms could also be involved in the process. In the presence of urea, Virgibacillus halodenitrificans CD6 exhibited the most efficient precipitation of CaCO3. However, the urease pathway has the disadvantage of producing ammonia, a toxic molecule. We showed herein that different marine bacteria could induce CaCO3 precipitation without urea. These bacteria could then be used for eco-friendly applications, e.g., the formation of bio-cements to strengthen dikes and delay coastal erosion.

Understanding biofouling and contaminant accretion on submerged marine structures

“…Due to the high precipitation potential and the extensive range of ureolytic bacteria across various environments, the urease and carbonic anhydrase (CA) based metabolic pathway is the most extensively studied form of MICP 4,55,56 . The ubiquity and relatively low complexity of the urease/CA metabolism has made it the model process for recent MICP studies on cathodically protected surfaces 3,4,57 . However, a recent study found that marine bacterial strains isolated from cathodically protected surfaces that tested positive for CA and negative for urease production was still able to undergo MICP in the absence of urea 3 .…”

“…The ubiquity and relatively low complexity of the urease/CA metabolism has made it the model process for recent MICP studies on cathodically protected surfaces 3,4,57 . However, a recent study found that marine bacterial strains isolated from cathodically protected surfaces that tested positive for CA and negative for urease production was still able to undergo MICP in the absence of urea 3 . This suggests CA may be critical in other MICP pathways, and that there is a need to expand past urease hydrolysis as the model for MICP, particularly in studies on subsea fouling.…”

“…As cathodic protection is a long-time and essential component of marine structures 2 , there is a need to understand the co-occurrent interactions that inevitably occur between electrochemical and microbial deposition 4 , as well as the settlement of subsequent biofouling communities on submerged infrastructure 10,58 . Within the marine environment, only a handful of marine biocalcifying bacterial strains from genera Bhargavaea, Epibacterium, Planococcus, Pseudidiomarina, Pseudoalteromonas, and Virgibacillus have been isolated from calcareous deposits formed from cathodic protection 3,57 . Additionally, studies on the interactions between MICP and electrochemical calcareous deposition, particularly within the natural marine environments is currently limited to model studies 4 .…”

“…Fouling is the adhesion of unwanted substances or contaminants onto surfaces and is an operational concern across various areas of industry 1 . Within maritime-based industries, where submerged marine structures are exposed to oceanic waters, the main sources of surface accumulation arise from calcareous deposits due to electrochemical reactions from cathodic protection systems 2 and biocalcifying bacteria 3,4 , as well as biological marine growth resulting from the formation of marine biofilms and subsequent settlement of macro-fouling organisms 5,6 . Economic losses in maritime-related industries sustained by fouling issues have necessitated the drive toward the development of effective antifouling coatings, with recent advances focusing on non-toxic, environmentally friendly alternatives for modern coatings 7,8 .…”

La biocalcification bactérienne en milieu marin et ses applications

“…Par exemple, la calcite a été observée sous forme de sphère, de chou-fleur et d'haltère dans de nombreuses expériences de laboratoire en présence de différentes bactéries (Fig. 2) [1] dont certaines d'origine marine [31,61].…”