Heterologous expression of the surface-layer-like protein SllB induces the formation of long filaments of Escherichia coli consisting of protein-stabilized outer membrane

Abstract

Escherichia coli is one of the best studied micro-organisms and is the most widely used host in genetic engineering. The Gram-negative single cells are rod-shaped, and filaments are usually not found. Here, we describe the reproducible formation of elongated E. coli cells. During heterologous expression of the silent surface (S)-layer protein gene sllB from Lysinibacillus sphaericus JG-A12 in E. coli BL21(DE3), the cells were arranged as long chains which were surrounded by highly stable sheaths. These filaments had a length of .100 mm. In the stationary growth phase, microscopic analyses demonstrated the formation of unusually long transparent tube-like structures which were enclosing separate single cells. The tube-like structures were isolated and analysed by SDS-PAGE, infrared-spectroscopy and different microscopic methods in order to identify their unusual composition and structure. The tube-like structures were found to be like outer membranes, containing high levels of proteins and to which the recombinant S-layer proteins were attached. Despite the entire structure being indicative of a disordered cell division, the bacterial cells were highly viable and stable. To our knowledge, this is the first time that the induction of drastic morphological changes in E. coli by the expression of a foreign protein has been reported.

Development of functionalised polyelectrolyte capsules using filamentous Escherichia coli cells

“…Previous studies discovered the formation of unusual long Escherichia coli cell filaments induced by S-layer protein expression [2,9]. Such biological structures provide a promising matrix for technical applications such as the development of microcontainers or hollow metallic microwires.…”

“…In molecular biology E. coli is generally used as a tool to produce proteins of interest of other organisms in a simple and high efficient way. In a previous study we described the formation of filamentous E. coli that are surrounded by tube-like structures consisting of outer membrane and surface (S-) layer proteins [2]. Although one of the best studied microorganisms only few reports describe the filament formation of Escherichia coli [3-6].…”

“…The filaments that have a uniform thickness of 0.8-1 μm and can reach a length of several 100 μm have been discussed as promising bio-template e.g. for the production of catalytic active composites or metal microwires [2,9]. …”

Novel Biotechnological Approaches for the Recovery of Metals from Primary and Secondary Resources

“…Upscale can be achieved by heterologous expression of the proteins in host cells [66][67][68] or optimization of isolation procedures. The recovery of bound precious metals is currently only possible via thermal decomposition (fuming), which is also carried out for corresponding ion exchange materials.…”

E. colifilament formation induced by heterologous S-layer expression

“…Interactions with the outer membranes require a secretion of the recombinant proteins. Though analyses of S-layer expression in the periplasm and supernatant as well as galactosidase assays during cultivation point to a secretion of the proteins, 21 the transport mechanism has not yet been identified.…”