Relationship Between Membrane Vesicles, Extracellular ATP and Biofilm Formation in Antarctic Gram-Negative Bacteria
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ENVIRONMENTAL MICROBIOLOGY
Relationship Between Membrane Vesicles, Extracellular ATP and Biofilm Formation in Antarctic Gram-Negative Bacteria Nicolas Baeza 1 & Elena Mercade 1 Received: 10 June 2020 / Accepted: 28 September 2020 # The Author(s) 2020
Abstract Biofilms offer a safe environment that favors bacterial survival; for this reason, most pathogenic and environmental bacteria live integrated in biofilm communities. The development of biofilms is complex and involves many factors, which need to be studied in order to understand bacterial behavior and control biofilm formation when necessary. We used a collection of cold-adapted Antarctic Gram-negative bacteria to study whether their ability to form biofilms is associated with a capacity to produce membrane vesicles and secrete extracellular ATP. In most of the studied strains, no correlation was found between biofilm formation and these two factors. Only Shewanella vesiculosa M7T secreted high levels of extracellular ATP, and its membrane vesicles caused a significant increase in the speed and amount of biofilm formation. In this strain, an important portion of the exogenous ATP was contained in membrane vesicles, where it was protected from apyrase treatment. These results confirm that ATP influences biofilm formation. Although the role of extracellular ATP in prokaryotes is still not well understood, the metabolic cost of its production suggests it has an important function, such as a role in biofilm formation. Thus, the liberation of extracellular ATP through membrane vesicles and its function deserve further study. Keywords Membrane vesicles . Gram-negative bacteria . Biofilm . Extracellular ATP . Antarctica
Introduction Gram-negative bacterial membrane vesicles (MVs) have been the subject of numerous studies in recent years [1, 2]. While there is growing evidence that more than one type of MV exists [3], MVs produced by Gram-negative bacteria are described as small (20–300 nm), spherical, bilayered membranous structures, derived from the outer membrane of the cell [4]. MV components, which can vary according to the strain and mechanism of formation, are mainly outer membrane lipids and proteins and periplasmic elements; inner membrane proteins and cytoplasmic compounds such as proteins, DNA or RNA may also be present [1, 5]. Along with this diversity of components, MVs are involved in several functions related to bacterial survival, pathogenicity, interaction
* Elena Mercade [email protected] 1
Secció de Microbiologia, Departament de Biologia, Sanitat i Medi Ambient, Universitat de Barcelona, Barcelona, Spain
with the host immune system, intercellular communication, and genetic transfer [1, 6, 7]. Both planktonic and sessile bacterial cells in biofilms can produce MVs [8]. Several studies have shown that MVs are ubiquitous in the extracellular matter of many Gram-negative bacterial biofilms [9, 10], and our group demonstrated the presence of huge amounts of MVs interspersed in the exopolymeric substance (EPS) secreted by cold-adapted Antarctic strain
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