No abstract

While bioengineers ask how the shape of diagnostic and therapeutic particles impacts their pharmacological efficiency, biodistribution, and toxicity, microbiologists suggested that morphological adaptations enable pathogens to perhaps evade the immune response. Here, a shape-dependent process is described that limits phagocytosis of filamentous Escherichia coli bacteria by macrophages: successful uptake requires access to one of the terminal bacterial filament poles. By exploiting micropatterned surfaces, we further demonstrate that microenvironmental heterogeneities can slow or inhibit phagocytosis. A comparison to existing literature reveals a common shape-controlled uptake mechanism for both high-aspect ratio filamentous bacteria and engineered particles.

To clear pathogens from host tissues or biomaterial surfaces, phagocytes have to break the adhesive bacteria-substrate interactions. Here we analysed the mechanobiological process that enables macrophages to lift-off and phagocytose surface-bound Escherichia coli (E. coli). In this opsonin-independent process, macrophage filopodia hold on to the E. coli fimbriae long enough to induce a local protrusion of a lamellipodium. Specific contacts between the macrophage and E. coli are formed via the glycoprotein CD48 on filopodia and the adhesin FimH on type 1 fimbriae (hook). We show that bacterial detachment from surfaces occurrs after a lamellipodium has protruded underneath the bacterium (shovel), thereby breaking the multiple bacterium-surface interactions. After lift-off, the bacterium is engulfed by a phagocytic cup. Force activated catch bonds enable the long-term survival of the filopodium-fimbrium interactions while soluble mannose inhibitors and CD48 antibodies suppress the contact formation and thereby inhibit subsequent E. coli phagocytosis.

Surface fouling, i.e. the non-specific surface adhesion of proteins, bacteria and higher organisms, poses a severe problem in many areas ranging from modern diagnostic and therapeutic medical devices to food processing and food wrapping technology to corrosion prevention and marine technology. One approach to address these problems is to coat surfaces with nonfouling polymers. The properties of a new class of nonfouling polymer coatings made from poly(2-methyl-2-oxazoline) (PMOXA) were investigated here in comparison with the most frequently used polymer in this context, poly(ethylene glycol) (PEG). Both polymers were side-chain grafted onto a polycationic poly-L-lysine (PLL) backbone. The PMOXA graft copolymers spontaneously self-assembled to form monolayers on negatively charged surfaces. PMOXA surface coatings were as efficient as PEG-based coatings in suppressing protein and bacterial adsorption. The minimal number of side chain monomer units per surface area that are needed to obtain fully resistant surfaces was lower though for PMOXA than for PEG graft copolymers as a result of the higher molecular weight of the PMOXA monomer unit.

Sessile bacteria adhere to engineered surfaces and host tissues and pose a substantial clinical and economical risk when growing into biofilms. Most engineered and biological interfaces are of chemically heterogeneous nature and provide adhesive islands for bacterial attachment and growth. To mimic either defects in a surface coating of biomedical implants or heterogeneities within mucosal layers (Peyer's patches), we embedded micrometre-sized adhesive islands in a poly(ethylene glycol) biopassive background. We show experimentally and computationally that filamentation of Escherichia coli can significantly accelerate the bacterial surface colonization under physiological flow conditions. Filamentation can thus provide an advantage to a bacterial population to bridge non-adhesive distances exceeding 5 µm. Bacterial filamentation, caused by blocking of bacterial division, is common among bacterial species and can be triggered by environmental conditions or antibiotic treatment. While great awareness exists that the build-up of antibiotic resistance serves as intrinsic survival strategy, we show here that antibiotic treatment can actually promote surface colonization by triggering filamentation, which in turn 1 Authors contributed equally to this work.

and Burkovski, Andreas (2019) Proteomics of diphtheria toxoid vaccines reveals multiple proteins that are immunogenic and may contribute to protection of humans against Corynebacterium diphtheriae. Vaccine, 37 (23). pp. 3061-3070.

The genus Corynebacterium includes species of biotechnological, medical and veterinary importance. An atypical C. ulcerans strain, W25, was recently isolated from a case of necrotizing lymphadenitis in a wild boar. In this study, we have analysed the genome sequence of this strain and compared the phenotypic and virulence properties with other corynebacterial pathogens. Phylogenomic analyses revealed that strain W25 belongs to a novel species along with PO100/5 and KL1196. The latter strains were isolated from a pig and a roe deer, respectively; hence, this species appears to be associated to animals. The isolate W25 is likely a nontoxigenic tox gene bearing strain and may have compromised abilities to adhere to pharyngeal and laryngeal epithelial cells due to potential loss of the gene functions in spaBC and spaDEF pilus gene clusters. A number of corynebacterial virulence genes are present including pld encoding phospholipase D. Therefore, this strain may be able to cause severe invasive infections in animals and zoonotic infections in humans.

Clostridium tetani is the etiological agent of tetanus, a life-threatening bacterial infection. The most efficient protection strategy against tetanus is a vaccination with the C. tetani neurotoxin, which is inactivated by formaldehyde-crosslinking. Since we assumed that besides the tetanus toxin, other proteins of C. tetani may also be present in toxoid preparations, we analyzed commercially available vaccines from different countries in respect to their protein content using mass spectrometry. In total 991 proteins could be identified in all five analyzed vaccines, 206 proteins were common in all analyzed vaccines and 54 proteins from the 206 proteins were potential antigens. The additionally present proteins may contribute at least partially to protection against C. tetani infection by supporting the function of the vaccine against the devastating effects of the tetanus toxin indirectly. Two different label-free protein quantification methods were applied for an estimation of protein contents. Similar results were obtained with a Total Protein Approach (TPA)-based method and Protein Discoverer 2.2 software package based on the minora algorithm. Depending on the tetanus toxoid vaccine and the quantification method used, tetanus neurotoxin contributes between 14 and 76 % to the total C. tetani protein content and varying numbers of other C. tetani proteins were detected.