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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 [micro]m. 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. DOI 10.1099/mic.0.040808-0

Abstract Background Escherichia coli is one of the best studied microorganisms and finds multiple applications especially as tool in the heterologous production of interesting proteins of other organisms. The heterologous expression of special surface (S-) layer proteins caused the formation of extremely long E. coli cells which leave transparent tubes when they divide into single E. coli cells. Such natural structures are of high value as bio-templates for the development of bio-inorganic composites for many applications. In this study we used genetically modified filamentous Escherichia coli cells as template for the design of polyelectrolyte tubes that can be used as carrier for functional molecules or particles. Diversity of structures of biogenic materials has the potential to be used to construct inorganic or polymeric superior hybrid materials that reflect the form of the bio-template. Such bio-inspired materials are of great interest in diverse scientific fields like Biology, Chemistry and Material Science and can find application for the construction of functional materials or the bio-inspired synthesis of inorganic nanoparticles. Results Genetically modified filamentous E. coli cells were fixed in 2% glutaraldehyde and coated with alternating six layers of the polyanion polyelectrolyte poly(sodium-4styrenesulfonate) (PSS) and polycation polyelectrolyte poly(allylamine-hydrochloride) (PAH). Afterwards we dissolved the E. coli cells with 1.2% sodium hypochlorite, thus obtaining hollow polyelectrolyte tubes of 0.7 μm in diameter and 5–50 μm in length. For functionalisation the polyelectrolyte tubes were coated with S-layer protein polymers followed by metallisation with Pd(0) particles. These assemblies were analysed with light microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. Conclusion The thus constructed new material offers possibilities for diverse applications like novel catalysts or metal nanowires for electrical devices. The novelty of this work is the use of filamentous E. coli templates and the use of S-layer proteins in a new material construct.

ABSTRACT Innovative approaches to the separation of minerals and subsequent extraction of metals are imperative owing to the increasing mineralogical complexity of ore deposits that are difficult or even impossible to separate into slurries or solutions containing only the minerals or metals of interest. Low recovery of metal is typical for these complex deposits leading to significant losses to tailings. In addition, the minerals often contain impurities, some toxic, which are difficult and costly to control or manage during the processing of a concentrate or other mineral product. One example of this complex situation is the significant economic and environmental costs associated with diluting and processing copper concentrates containing arsenic (in the form of the mineral enargite, Cu3AsS4) in the production of pure copper. To overcome these separation problems, we have utilized phage display to identify peptides that demonstrate selective recognition of enargite and the arsenic-free copper sulfide, chalcopyrite. Screening of two random peptide phage display libraries resulted in the identification of an enargite-selective peptide with the sequence MHKPTVHIKGPT and a chalcopyrite-selective peptide with the sequence RKKKCKGNCCYTPQ. Mineral-binding selectivity was demonstrated by binding studies, zeta potential determination and immunochemistry. Peptides that have the ability to discriminate between enargite and chalcopyrite provide a greener option for the separation of arsenic containing contaminants from copper concentrates. This represents the first step towards a major advance in the replacement or reduction of toxic collectors as well as reducing the level of arsenic-bearing minerals in the early stages of mineral processing. Biotechnol. Bioeng. 2017;114: 998-1005. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Escherichia coli is a rod-shaped intestinal bacterium which has a size of 1.1-1.5 µm x 2.0-6.0 µm. The fast cell division process and the uncomplicated living conditions have turned E. coli into a widely used host in genetic engineering and into one of the best studied microorganisms of all. We used E. coli BL21(DE3) as host for heterologous expression of S-layer proteins of Lysinibacillus sphaericus JG-A12 in order to enable a fast and high efficient protein production. The S-layer expression induced in E. coli an unusual elongation of the cells, thus producing filaments of > 100 µm in length. In the stationary growth phase, E. coli filaments develop tube-like structures that contain E. coli single cells. Fluorescence microscopic analyses of S-layer expressing E. coli cells that were stained with membrane stain FM (®) 5-95 verify the membrane origin of the tubes. Analyses of DAPI stained GFP-S-layer expressing E. coli support the assumption of a disordered cell division that is induced by the huge amount of recombinant S-layer proteins. However, the underlying mechanism is still not characterized in detail. These results describe the occurrence of a novel stable cell form of E. coli as a result of a disordered cell division process.