Membrane vesicles in sea water: heterogeneous DNA content and implications for viral abundance estimates.
Diverse microbes release membrane-bound extracellular vesicles from their outer surfaces into the surrounding environment. Vesicles are found in numerous habitats including the oceans, where they likely have a variety of functional roles in microbial ecosystems. Extracellular vesicles are known to contain a range of biomolecules including DNA, but the frequency with which DNA is packaged in vesicles is unknown. Here, we examine the quantity and distribution of DNA associated with vesicles released from five different bacteria. The average quantity of double-stranded DNA and size distribution of DNA fragments released within vesicles varies among different taxa. Although some vesicles contain sufficient DNA to be visible following staining with the SYBR fluorescent DNA dyes typically used to enumerate viruses, this represents only a small proportion (<0.01-1%) of vesicles. Thus DNA is packaged heterogeneously within vesicle populations, and it appears that vesicles are likely to be a minor component of SYBR-visible particles in natural sea water compared with viruses. Consistent with this hypothesis, chloroform treatment of coastal and offshore seawater samples reveals that vesicles increase epifluorescence-based particle (viral) counts by less than an order of magnitude and their impact is variable in space and time.
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
Steven J
SJ
Biller
College of Marine Science, University of South Florida, St Petersburg, FL, USA.
Lauren D
LD
McDaniel
College of Marine Science, University of South Florida, St Petersburg, FL, USA.
Mya
M
Breitbart
College of Marine Science, University of South Florida, St Petersburg, FL, USA.
Everett
E
Rogers
College of Marine Science, University of South Florida, St Petersburg, FL, USA.
John H
JH
Paul
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.|Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
Sallie W
SW
Chisholm
D001419:Bacteria / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D002725:Chloroform / Q000494:pharmacology; D004247:DNA / Q000032:analysis; D017753:Ecosystem; D009792:Oceans and Seas; D012623:Seawater / Q000382:microbiology*; D014780:Viruses / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification
D002725:Chloroform; D004247:DNA