Characterization of ExeM, an Extracellular Nuclease of Shewanella oneidensis MR-1

Abstract

Bacterial extracellular nucleases have multiple functions in processes as diverse as nutrient acquisition, natural transformation, biofilm formation, or defense against neutrophil extracellular traps (NETs). Here we explored the properties of ExeM in Shewanella oneidensis MR-1, an extracellular nuclease, which is widely conserved among species of Shewanella, Vibrio, Aeromonas, and others. In S. oneidensis, ExeM is crucial for normal biofilm formation. In vitro activity measurements on heterologously produced ExeM revealed that this enzyme is a sugar-unspecific endonuclease, which requires Ca2+ and Mg2+/Mn2+ as co-factors for full activity. ExeM was almost exclusively localized to the cytoplasmic membrane fraction, even when a putative C-terminal membrane anchor was deleted. In contrast, ExeM was not detected in medium supernatants. Based on the results we hypothesize that ExeM predominantly interacts with DNA in close proximity to the cell, e.g., to promote biofilm formation and defense against NETs, or to control uptake of DNA.

Degradation of biological macromolecules supports uncultured microbial populations in Guaymas Basin hydrothermal sediments

“…Although DNA and lipids are energy-rich and abundant in marine sediments [ 9 ], the identity and distribution of nucleases and lipases across genomes, organisms and databases is not well characterized, in contrast to the enzymes involved in the breakdown of proteins [ 92 , 93 ] and polysaccharides [ 94 , 95 ]. Few studies have identified bacterial extracellular nucleases [ 96 , 97 ] and lipases [ 98 ] associated with catabolic activities. Furthermore, nucleases and lipases can also participate in synthesis and salvage pathways, and are not necessarily involved in catabolism [ 99 , 100 ].…”

Fitness of Outer Membrane Vesicles From Komagataeibacter intermedius Is Altered Under the Impact of Simulated Mars-like Stressors Outside the International Space Station

“…Enhanced DNAse activities observed in OMVs from post-spaceflight re-isolates correlated with a poor biofilm production in parental bacteria, when the activity of such nucleases was demonstrated to balance the extent of biofilm formation, and this is congruent with the previously published results by Sharma and Singh (2018) . Nucleases also contribute to the lower bacterial transformation capability of different bacteria, preventing horizontal gene transfer ( Binnenkade et al, 2018 ; Jhelum et al, 2018 ). The nuclease-associated OMVs of the dominant KMC K. intermedius can be represented as safeguards, keeping the essential genome stability in this microecosystem.…”

Characterization of Vibrio cholerae’s Extracellular Nuclease Xds

“…Consistent with a previous report (Seper et al, 2011), the nuclease assay used herein confirmed that Xds has exonuclease activity only capable of degrading linear DNA but not circular DNA. In contrast ExeM of Shewanella oneidensis , a homolog of Xds with 41% identity, was recently characterized to have sugar-unspecific endonuclease activity (Binnenkade et al, 2018). With 94.3 kDa Xds represents a relatively high molecular weight multi-domain enzyme.…”