Blood platelets are critical for hemostasis and thrombosis and play diverse roles during immune responses. Despite these versatile tasks in mammalian biology, their skills on a cellular level are deemed limited, mainly consisting in rolling, adhesion, and aggregate formation. Here, we identify an unappreciated asset of platelets and show that adherent platelets use adhesion receptors to mechanically probe the adhesive substrate in their local microenvironment. When actomyosin-dependent traction forces overcome substrate resistance, platelets migrate and pile up the adhesive substrate together with any bound particulate material. They use this ability to act as cellular scavengers, scanning the vascular surface for potential invaders and collecting deposited bacteria. Microbe collection by migrating platelets boosts the activity of professional phagocytes, exacerbating inflammatory tissue injury in sepsis. This assigns platelets a central role in innate immune responses and identifies them as potential targets to dampen inflammatory tissue damage in clinical scenarios of severe systemic infection.

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There is evidence for an age-related decline in male reproductive functions, yet how the human testis may age is not understood. Human testicular peritubular cells (HTPCs) transport sperm, contribute to the spermatogonial stem cell (SSC) niche and immune surveillance, and can be isolated and studied in vitro. Consequences of replicative senescence of HTPCs were evaluated to gain partial insights into human testicular aging. To this end, early and advanced HTPC passages, in which replicative senescence was indicated by increased cell size, altered nuclear morphology, enhanced β-galactosidase activity, telomere attrition and reduced mitochondrial DNA (mtDNA), were compared. These alterations are typical for senescent cells, in general. To examine HTPC-specific changes, focused ion beam scanning electron microscopy (FIB/SEM) tomography was employed, which revealed a reduced mitochondrial network and an increased lysosome population. The results coincide with the data of a parallel proteomic analysis and indicate deranged proteostasis. The mRNA levels of typical contractility markers and growth factors, important for the SSC niche, were not significantly altered. A secretome analysis identified, however, elevated levels of macrophage migration inhibitory factor (MIF) and dipeptidyl peptidase 4 (DPP4), which may play a role in spermatogenesis. Testicular DPP4 may further represent a possible drug target.

Members of the metabolically diverse order Nitrosomonadales inhabit a wide range of environments. Two strains affiliated with this order were isolated from soils in Germany and characterized by a polyphasic approach. Cells of strains 0125_3T and Swamp67T are Gram-negative rods, non-motile, non-spore-forming, non-capsulated and divide by binary fission. They tested catalase-negative, but positive for cytochrome c-oxidase. Both strains form small white colonies on agar plates and grow aerobically and chemoorganotrophically on SSE/HD 1 : 10 medium, preferably utilizing organic acids and proteinaceous substrates. Strains 0125_3T and Swamp67T are mesophilic and grow optimally without NaCl addition at slightly alkaline conditions. Major fatty acids are C16 : 1  ω7c, C16 : 0 and C14 : 0. The major polar lipids are diphosphatidylglycerol, phosphatidylethanolamine and phosphatidyglycerol. The predominant respiratory quinone is Q-8. The G+C content for 0125_3T and Swamp67T was 67 and 66.1 %, respectively. The 16S rRNA gene analysis indicated that the closest relatives (<91 % sequence similarity) of strain 0125_3T were Nitrosospira multiformis ATCC 25196T, Methyloversatilis universalis FAM5T and Denitratisoma oestradiolicum AcBE2-1T, while Nitrosospira multiformis ATCC 25196T, Nitrosospira tenuis Nv1T and Nitrosospira lacus APG3T were closest to strain Swamp67T. The two novel strains shared 97.4 % 16S rRNA gene sequence similarity with one another and show low average nucleotide identity of their genomes (83.8 %). Based on the phenotypic, chemotaxonomic, genomic and phylogenetic analysis, we propose the two novel species Usitatibacter rugosus sp. nov (type strain 0125_3T=DSM 104443T=LMG 29998T=CECT 9241T) and Usitatibacter palustris sp. nov. (type strain Swamp67T=DSM 104440T=LMG 29997T=CECT 9242T) of the novel genus Usitatibacter gen. nov., within the novel family Usitatibacteraceae fam. nov.