Surface analysis of biological systems using XPS often requires dehydration of the sample for it to be compatible with the ultrahigh vacuum of the spectrometer. However, if samples are frozen to liquid-nitrogen temperature prior to and during analysis, water can be retained in the sample and the organization of the sample surface should be preserved to a higher degree than in desiccated samples. This article presents recent developments of cryo-X-ray photoelectron spectroscopy (cryo-XPS) for analyses of hydrated biological samples at liquid nitrogen temperature. We describe experiments on bacterial cells, bacterial biofilms, and bacterial outer membrane vesicles using a variety of bacterial species. Differences and similarities in surface chemistry are monitored depending on growth in liquid culture, on culture plates, as well as in biofilms, and are discussed. Two data treatment methods providing decomposition of the C 1s spectra into lipid, polysaccharide, and peptide/peptidoglycan content are used and compared.

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<p><strong>Pharmaceuticals and biofilms in a fresh-water stream in the south of Sweden</strong></p> <p><strong>Aleksandra Hagberg<sup>1</sup></strong>, Shashank Gupta<sup>2</sup>, Olena Rzhepishevska<sup>1</sup>, Jerker Fick<sup>1</sup>, Mette Burmølle<sup>2</sup>, Madeleine Ramstedt<sup>1</sup></p> <ul> <li>1) Department of Chemistry, Umeå Center for Microbial Research, Umeå University, 901 87 Umeå, Sweden</li> <li>2) Section of Microbiology, Department of Biology, University of Copenhagen, 2100, Copenhagen, Denmark</li> </ul> <p> </p> <p>Pharmaceuticals have been detected in the aquatic environment all around the globe. The usage of medicine is growing every year, increasing the number of pharmaceutical residues released into the environment. Chronic exposure creates a significant threat to aquatic organisms. For this reason, it is crucial to investigate how pharmaceuticals can affect inhabitants of the aquatic ecosystem. In our study, we aimed to investigate how pharmaceuticals influenced the sessile bacterial species pattern in the Knivsta river in the south of Sweden. By placing the four sampling points before and after contamination (upstream and downstream), we aimed to see differences between locations that were chronically exposed to pharmaceuticals from a local sewage treatment plant and those that remained unexposed. Sampling was made three times in one year. Bacterial populations were analyzed by sequencing 16S RNA. Water chemistry with respect to pharmaceutical content was determined with LC-MS. Bacterial isolates were also collected and showed a range of phenotypes.</p> <p> </p>