NanoSIMS 50L

Secondary ion mass spectrometry (SIMS) is a surface analysis technique. It provides information about the lateral distribution of any element and its isotopes as well as a quantitative information about the isotopic composition of a sample. Using a well focused ion beam the sample surface is bombarded with primary ions and secondary ions sputtered from the sample are analysed in a mass spectrometer.

The Max Planck Institute for Marine Microbiology finished the installation of a NanoSIMS 50L in March 2008. The funding for the acquisition of this instrument was provided by the Innovation Fund of the Max Planck Society.

The NanoSIMS 50L is equipped with Cs+ and O- primary ion sources, an electron gun for analysis of insulating samples, a secondary electron detector, and a magnetic sector mass analyser with a large version of the magnet and a multi-collection system of 7 detectors all equipped with Faraday cups and electron multiplier detectors. This configuration allows us the possiblity of analysing any mass from helium to uranium as well as molecules and clusters of atoms.

The NanoSIMS 50L is a nanometer scale secondary ion mass spectrometer with both extremely high lateral resolution and high mass resolution. Because of a unique ion optic design, the primary ion beam can be focused to a very small spot down to less than 50nm beam size. The high mass resolution of the mass analyser allows the separation of the isotope (mass) of interest from interferencing isotopes and/or molecular clusters with very close masses.

For more information on the unique capabilities of the NanoSIMS 50L in environmental microbiology applications, please visit our project pages.

Prior to a nanoSIMS ana­lysis, fields of view con­tain­ing cells of in­terest are marked us­ing the laser mi­cro­dissec­tion mi­cro­scope (Leica LMD 6500). This fa­cil­it­ates sample ori­ent­a­tion dur­ing nanoSIMS ana­lysis.

The laser microdissection microscope (LMD) is equipped with vari­ous air ob­ject­ives (10x - 63x) and fluor­es­cent fil­ters (i.e. DAPI, Cy3, Cy5, Al­ex­a594) to identify, mark and cut out single cells us­ing a UV laser (wave length: 355 nm, pulse fre­quency: 80 Hz, pulse length: <4 ns, avg. pulse en­ergy 70 μJ). Imges of the marked areas are re­cor­ded us­ing a CC7000 color cam­era.

While ox­id­iz­ing meth­ane, aer­obic meth­an­o­trophic bac­teria also as­sim­il­ate meth­ane car­bon into their bio­mass. When in­cub­ated in the pres­ence of ¹³C-labeled meth­ane, active methanotrophic bacteria can be iden­ti­fied by their high cel­lu­lar ¹³C/¹²C ra­tios. In this case, a wa­ter column sample from a strat­i­fied Lake Cadagno was ana­lyzed. Ar­rows in­dic­ate gamma-pro­teo­bac­terial meth­an­o­trophs. Cor­res­pond­ing ¹³C/¹²C an ³²S/¹²C nanoSIMS im­ages show as­sim­il­a­tion of ¹³C-la­belled meth­ane and the dis­tri­bu­tion of cell bio­mass, re­spect­ively.

Our cur­rent pro­jects in­volving nanoSIMS for study of meth­ane ox­id­a­tion can be found HERE.

By re­cord­ing the ¹²C¹⁵N/¹²C¹⁴N and ¹³C/¹²C ra­tios of in­di­vidual cells, es­tim­ates of in­di­vidual single-cell carbon and N₂ fixation rates can be made. Here, car­bon and N₂ fix­a­tion rates of uni­cel­lu­lar Crocosphaera watsonii-like cy­anobac­terial cells from the sub­trop­ical North Pa­cific Gyre were meas­ured. These were one of the first dir­ect in situ activ­ity meas­ure­ments of these im­port­ant diazo­trophs.

Our cur­rent pro­jects in­volving nanoSIMS for study of ni­tro­gen fix­a­tion can be found HERE.