title: A Submersible, Off-Axis Holographic Microscope for Detection of Microbial Motility and Morphology in Aqueous and Icy Environments.
abstract: Sea ice is an analog environment for several of astrobiology's near-term targets: Mars, Europa, Enceladus, and perhaps other Jovian or Saturnian moons. Microorganisms, both eukaryotic and prokaryotic, remain active within brine channels inside the ice, making it unnecessary to penetrate through to liquid water below in order to detect life. We have developed a submersible digital holographic microscope (DHM) that is capable of resolving individual bacterial cells, and demonstrated its utility for immediately imaging samples taken directly from sea ice at several locations near Nuuk, Greenland. In all samples, the appearance and motility of eukaryotes were conclusive signs of life. The appearance of prokaryotic cells alone was not sufficient to confirm life, but when prokaryotic motility occurred, it was rapid and conclusive. Warming the samples to above-freezing temperatures or supplementing with serine increased the number of motile cells and the speed of motility; supplementing with serine also stimulated chemotaxis. These results show that DHM is a useful technique for detection of active organisms in extreme environments, and that motility may be used as a biosignature in the liquid brines that persist in ice. These findings have important implications for the design of missions to icy environments and suggest ways in which DHM imaging may be integrated with chemical life-detection suites in order to create more conclusive life detection packages.
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91125, United States of America.
authors.forename: Christian A
authors.initials: CA
authors.lastname: Lindensmith
authors.affiliation: Graduate Aerospace Laboratories (GALCIT), California Institute of Technology, Pasadena, California, 91125, United States of America.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Rider
authors.affiliation: Graduate Aerospace Laboratories (GALCIT), California Institute of Technology, Pasadena, California, 91125, United States of America.
authors.forename: Manuel
authors.initials: M
authors.lastname: Bedrossian
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91125, United States of America.
authors.forename: J Kent
authors.initials: JK
authors.lastname: Wallace
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91125, United States of America.
authors.forename: Eugene
authors.initials: E
authors.lastname: Serabyn
authors.affiliation: School of Oceanography, University of Washington, Seattle, Washington, 98195, United States of America.
authors.forename: G Max
authors.initials: GM
authors.lastname: Showalter
authors.affiliation: School of Oceanography, University of Washington, Seattle, Washington, 98195, United States of America.
authors.forename: Jody W
authors.initials: JW
authors.lastname: Deming
authors.affiliation: Graduate Aerospace Laboratories (GALCIT), California Institute of Technology, Pasadena, California, 91125, United States of America.
authors.forename: Jay L
authors.initials: JL
authors.lastname: Nadeau
mesh_terms: D002633:Chemotaxis; D017753:Ecosystem; D005057:Eukaryotic Cells / Q000502:physiology; D006116:Greenland; D006696:Holography; D046448:Ice Cover / Q000382:microbiology*; D008828:Microbiological Techniques / Q000295:instrumentation*; D008853:Microscopy; D011387:Prokaryotic Cells / Q000502:physiology; D012694:Serine / Q000737:chemistry / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D012694:Serine
references.citation: Proc Natl Acad Sci U S A. 2000 Feb 1;97(3):1247-51
references.pmid: 10655516
references.citation: Appl Environ Microbiol. 2000 Aug;66(8):3214-20
references.pmid: 10919772
references.citation: Appl Environ Microbiol. 2003 Apr;69(4):2153-60
references.pmid: 12676695
references.citation: Astrobiology. 2003 Summer;3(2):331-41
references.pmid: 14577882
references.citation: Appl Environ Microbiol. 2004 Jan;70(1):550-7
references.pmid: 14711687
references.citation: FEMS Microbiol Ecol. 2005 Jun 1;53(1):117-28
references.pmid: 16329934
references.citation: FEMS Microbiol Ecol. 2006 Jan;55(1):3-16
references.pmid: 16420610
references.citation: Appl Environ Microbiol. 1995 Mar;61(3):877-82
references.pmid: 16534971
references.citation: Extremophiles. 2006 Aug;10(4):259-67
references.pmid: 16550305
references.citation: Astrobiology. 2006 Feb;6(1):69-86
references.pmid: 16551227
references.citation: FEMS Microbiol Ecol. 2007 Feb;59(2):307-17
references.pmid: 17313580
references.citation: FEMS Microbiol Ecol. 2007 Feb;59(2):217-31
references.pmid: 17328118
references.citation: Proc Natl Acad Sci U S A. 2007 Oct 30;104(44):17512-7
references.pmid: 17959778
references.citation: Opt Lett. 2008 Jul 15;33(14):1626-8
references.pmid: 18628819
references.citation: Mikrobiologiia. 2009 Jan-Feb;78(1):98-105
references.pmid: 19334602
references.citation: Opt Express. 2005 Sep 5;13(18):6738-49
references.pmid: 19498690
references.citation: Environ Microbiol. 2010 Jul;12(7):1828-41
references.pmid: 20192970
references.citation: Opt Lett. 2010 Jun 1;35(11):1840-2
references.pmid: 20517434
references.citation: Res Microbiol. 2011 Apr;162(3):346-61
references.pmid: 21187146
references.citation: Proc Natl Acad Sci U S A. 2011 Mar 1;108(9):3653-8
references.pmid: 21368216
references.citation: Environ Microbiol. 2011 Aug;13(8):2269-78
references.pmid: 21535342
references.citation: Methods Enzymol. 2012;504:183-200
references.pmid: 22264535
references.citation: Nat Methods. 2012 Jun 28;9(7):676-82
references.pmid: 22743772
references.citation: Astrobiology. 2013 Apr;13(4):334-53
references.pmid: 23560417
references.citation: Astrobiology. 2013 Aug;13(8):740-73
references.pmid: 23924246
references.citation: Nat Rev Microbiol. 2014 Jun;12(6):414-25
references.pmid: 24814065
references.citation: Biology (Basel). 2013 Mar 28;2(2):603-28
references.pmid: 24832800
references.citation: Rev Sci Instrum. 2014 Dec;85(12):123113
references.pmid: 25554278
references.citation: Front Microbiol. 2015 Mar 24;6:225
references.pmid: 25852678
references.citation: Opt Express. 2015 Jun 29;23(13):17367-78
references.pmid: 26191746
references.citation: Nat Rev Microbiol. 2015 Nov;13(11):677-90
references.pmid: 26344407
references.citation: FEMS Microbiol Ecol. 2016 May;92(5):fiw053
references.pmid: 26976841