TY - JOUR A1 - Kjaervik, Marit A1 - Ramstedt, M. A1 - Schwibbert, Karin A1 - Dietrich, P. M A1 - Unger, Wolfgang T1 - Comparative Study of NAP-XPS and Cryo-XPS for the Investigation of Surface Chemistry of the Bacterial Cell-Envelope N2 - Bacteria generally interact with the environment via processes involving their cell-envelope. Thus, techniques that may shed light on their surface chemistry are attractive tools for providing an understanding of bacterial interactions. One of these tools is Al Kα-excited photoelectron spectroscopy (XPS) with its estimated information depth of <10 nm. XPS-analyses of bacteria have been performed for several decades on freeze-dried specimens in order to be compatible with the vacuum in the analysis chamber of the spectrometer. A limitation of these studies has been that the freeze-drying method may collapse cell structure as well as introduce surface contaminants. However, recent developments in XPS allow for analysis of biological samples at near ambient pressure (NAP-XPS) or as frozen hydrated specimens (cryo-XPS) in vacuum. In this work, we have analyzed bacterial samples from a reference strain of the Gram-negative bacterium Pseudomonas fluorescens using both techniques. We compare the results obtained and, in general, observe good agreement between the two techniques. Furthermore, we discuss advantages and disadvantages with the two analysis approaches and the output data they provide. XPS reference data from the bacterial strain are provided, and we propose that planktonic cells of this strain (DSM 50090) are used as a reference material for surface chemical analysis of bacterial systems. KW - P. Fluorescens KW - Cryo XPS KW - NAP-XPS KW - DSM 5009 PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-525640 VL - 9 SP - Article 666161 PB - Frontiers CY - Switzerland AN - OPUS4-52564 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Dietrich, P. A1 - Beblo-Vranesevic, K. A1 - Kjærvik, Marit A1 - Unger, Wolfgang A1 - Schwibbert, Karin A1 - Hardie, K. A1 - Brown, J. T1 - XPS surface analysis of bacterial samples N2 - This application note presents how EnviroESCA can be used to analyze bacterial samples under near ambient pressure conditions in various states of hydration using different levels of humidity. Such investigations of bacterial cell wall surfaces in their hydrated state are essential for studying biological interfaces at work. The use of innovative near-ambient pressure (NAP-)XPS instrumentation allows the detailed analysis of irregularly-surfaced biofilms. NAP-XPS enables the surface analysis of bacterial samples in their natural hydrated state without complex sample preparation techniques such as freeze-drying or fast-freezing, which are needed for XPS analysis in ultrahigh vacuum. KW - Near ambient pressure XPS KW - Biofilms PY - 2018 UR - http://www.enviroai.com/uploads/1/0/2/8/102861712/xps_surface_analysis_of_bacillus_subtilis_biofilms_final.pdf IS - Application Note #000399 SP - 1 EP - 5 CY - Berlin AN - OPUS4-44588 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kjaervik, Marit A1 - Schwibbert, Karin A1 - Dietrich, P. A1 - Thissen, A. A1 - Unger, Wolfgang T1 - Surface characterisation of Escherichia coli under various conditions by near-ambient pressure XPS N2 - Bacteria are inherently in a hydrated state and therefore not compatible to ultra-high vacuum techniques such as XPS without prior sample preparation involving freeze drying or fast freezing. This has changed with the development of near-ambient pressure (NAP)-XPS, which makes it possible to characterise the bacterial surface with minimal sample preparation. This paper presents NAP-XPS measurements of Escherichia coli under various NAP conditions: at 11 mbar in a humid environment, at 2 mbar after drying in the chamber, pre-dried at 4 mbar, and at 1 mbar after overnight pumping at 10^−4 mbar. The high-resolution spectra of carbon, nitrogen, and oxygen are presented and found to be in general agreement with XPS measurements from freeze-dried and fast-frozen bacteria. However, it was found that the amount of carbon components associated with polysaccharides increases relative to aliphatic carbon during drying and increases further after overnight pumping. This implies that drying has an impact on the bacterial surface. T2 - European conference on applications of surface and interface analysis (ECASIA'17) CY - Montpellier, France DA - 24.09.2018 KW - Bacteria KW - E. coli KW - NAP-XPS PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-454047 SN - 0142-2421 SN - 1096-9918 VL - 50 IS - 11 SP - 996 EP - 1000 PB - John Wiley & Sons CY - Hoboken, New Jersey, USA AN - OPUS4-45404 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kjaervik, Marit A1 - Schwibbert, Karin A1 - Dietrich, P. A1 - Thissen, A. A1 - Unger, Wolfgang T1 - Near-ambient pressure XPS of hydrated Escherichia coli samples with EnviroESCA N2 - This application note presents how EnviroESCA can be used to analyze E. coli biofilms on silicon under near ambient pressure conditions in various states of hydration. Such investigations of the outer bacterial cell surface in their hydrated state are essential for studying biological interfaces at work. KW - Biofilms KW - E. coli KW - NAP-XPS PY - 2018 UR - http://www.enviroai.com/uploads/1/0/2/8/102861712/nap_xps_of_escherichia_coli_samples.pdf IS - Application Note #000400 SP - 1 EP - 4 CY - Berlin, Germany AN - OPUS4-45720 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kjaervik, Marit A1 - Schwibbert, Karin A1 - Dietrich, P.M. A1 - Unger, Wolfgang T1 - NAP-XPS spectra of the bacterial cell-envelope of Pseudomonas fluorescens bacteria N2 - Pseudomonas fluorescens (Gram-negative) bacteria purchased from Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures were analyzed using high-resolution x-ray photoelectron spectroscopy at near ambient pressure conditions (NAP-XPS), 1500 Pa water vapor atmosphere. Fresh layers of P. fluorescence bacteria were grown on Luria Broth agar plates. Bacteria were taken from the agar plate with a sterile spatula and gently spread on a Si-wafer piece for NAP-XPS analysis. The NAP-XPS spectra of the bacterial envelope of P. fluorescence were obtained using monochromatic Al Kα radiation and include a survey scan and high-resolution spectra of C 1s, N 1s, P 2p, and O 1s as well. The presentation of the C 1s high-resolution spectrum includes the results of peak fitting analysis. KW - Pseudomonas fluorescens KW - Cell-envelope KW - Water atmosphere KW - Near ambient x-ray photoelectron spectroscopy KW - NAP-XPS PY - 2022 U6 - https://doi.org/10.1116/6.0001543 SN - 1055-5269 VL - 29 IS - 1 SP - 014008-1 PB - AVS AN - OPUS4-54464 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -