Biology subjects

Nonnenmann, S. S.

Publications and source records attributed to Nonnenmann, S. S..

6 recordsLinked to original sources

bioRxiv2024

Incorporating Microbial Pilin-Based Nanowires into a Water-Stable Electronic Polymer Composite

Electrically conductive protein nanowires (e-PNs), microbially produced from a pilin monomer, are a novel, sustainable electronic material that can be genetically tailored for specific functions. e-PNs, expressed with Escherichia coli grown on the biodiesel byproduct glycerol, and mixed with polyvinyl butyral yielded a transparent, electrically conductive water-stable composite.Composite conductivity was adjusted by modifying the e-PN concentration or incorporating e-PNs genetically tuned for different conductivities. Electronic devices in which composites were the sensor component differentially responded to dissolved ammonia over a wide concentration range (1{micro}M-1M). Genetically modifying e-PNs to display an ammonia-binding peptide on their outer surface increased the sensor response to ammonia 10-fold. These results, coupled with the flexibility to design peptides for specific binding of diverse analytes, demonstrate that sustainably produced e-PNs offer the possibility of incorporating multiple sensor components, each specifically designed to detect different analytes with high sensitivity and selectivity, within one small sensor device.

bioengineering↗

bioRxiv2021

Pili Expression in Geobacter sulfurreducens Lacking the Putative Gene for the PilB Pilus Assembly Motor

Multiple lines of evidence suggest that electrically conductive pili (e-pili) are an important conduit for long-range electron transport in Geobacter sulfurreducens, a common model microbe for the study of extracellular electron transport mechanisms. One strategy to study the function of e-pili has been to delete the gene for PilB, the pilus assembly motor protein, in order to prevent e-pili expression. However, we found that e-pili are still expressed after the gene for PilB is deleted. Conducting probe atomic force microscopy revealed filaments with the same diameter and similar current-voltage response as e-pili harvested from wild-type G. sulfurreducens or when e-pili are heterologously expressed from the G. sulfurreducens pilin gene in E. coli. Immunogold labeling demonstrated that a G. sulfurreducens strain expressing e-pili with a His-tag continued to express His-tag labelled e-pili when the PilB gene was deleted. Strains with the PilB gene deleted produced maximum current densities comparable to wild-type controls. These results demonstrate that deleting the gene for PilB is not an appropriate strategy for constructing strains of G. sulfurreducens without e-pili, necessitating a reinterpretation of the results of previous studies that have employed this approach. ImportanceGeobacter sulfurreducens is a model microbe for the study of biogeochemically and technologically significant processes such as the reduction of Fe(III) oxides in soils and sediments; bioelectrochemical applications that produce electric current from waste organic matter or drive useful processes with the consumption of renewable electricity; direct interspecies electron transfer in anaerobic digestors and methanogenic soils and sediments; and metal corrosion. The phenotypes associated with gene deletions are an important strategy for determining the mechanisms for extracellular electron transfer in G. sulfurreducens. The results reported here demonstrate that a gene deletion previously thought to prevent the expression of electrically conductive pili in G. sulfurreducens does not have the intended result. Conductive pili continue to be expressed. This finding is important for interpreting the results of several previous studies on conductive pili function.

microbiology↗

bioRxiv2019

An Escherichia coli Chassis for Production of Electrically Conductive Protein Nanowires

Geobacter sulfurreducens pilin-based electrically conductive protein nanowires (e-PNs) are a revolutionary electronic material. They offer novel options for electronic sensing applications and have the remarkable ability to harvest electrical energy from atmospheric humidity. However, technical constraints limit mass cultivation and genetic manipulation of G. sulfurreducens. Therefore, we designed a strain of Escherichia coli to express e-PNs by introducing a plasmid that contained an inducible operon with E. coli genes for type IV pili biogenesis machinery and a synthetic gene designed to yield a peptide monomer that could be assembled into e-PNs. The e-PNs expressed in E. coli, and harvested with a simple filtration method, had the same diameter (3 nm) and conductance as e-PNs expressed in G. sulfurreducens. These results, coupled with the robustness of E. coli for mass cultivation and the extensive E. coli toolbox for genetic manipulation, greatly expands opportunities for large-scale fabrication of novel e-PNs.

synthetic biology↗

bioRxiv2019

Decorating Microbially Produced Protein Nanowires with Peptide Ligands

The potential applications of electrically conductive protein nanowires (e-PNs) harvested from Geobacter sulfurreducens might be greatly expanded if the outer surface of the wires could be modified to confer novel sensing capabilities or to enhance binding to other materials. We developed a simple strategy for functionalizing e-PNs with surface-exposed peptide ligands. The G. sulfurreducens gene for the monomer that assembles into e-PNs was modified to add known peptide ligands at the carboxyl terminus of the monomer. Strains of G. sulfurreducens were constructed that fabricated synthetic e-PNs with a six-histidine His-tag or both the His-tag and a nine-peptide HA-tag exposed on the outer surface. Addition of the peptide ligands did not diminish e-PN conductivity. The abundance of HA-tag in e-PNs was controlled by placing expression of the gene for the synthetic monomer with the HA-tag under transcriptional regulation. These studies suggest broad possibilities for tailoring e-PN properties for diverse applications.

synthetic biology↗

bioRxiv2018

Syntrophus Conductive Pili Demonstrate that Common Hydrogen-Donating Syntrophs can have a Direct Electron Transfer Option

Syntrophic interspecies electron exchange is essential for the stable functioning of diverse anaerobic microbial communities. Hydrogen/formate interspecies electron transfer (HFIT), in which H2 and/or formate function as diffusible electron carriers, has been considered to be the primary mechanism for electron sharing because most common syntrophs were thought to lack biochemical components, such as electrically conductive pili (e-pili), necessary for direct interspecies electron transfer (DIET). Here we report that Syntrophus aciditrophicus, one of the most intensively studied microbial models for HFIT, produces e-pili and can grow via DIET. Pilin genes likely to yield e-pili were found in other genera of hydrogen/formate-producing syntrophs. The finding that DIET is a likely option for diverse syntrophs that are abundant in many anaerobic environments necessitates a reexamination of the paradigm that HFIT is the predominant mechanism for syntrophic electron exchange within anaerobic microbial communities of biogeochemical and practical significance.

microbiology↗

bioRxiv2018

The Archaellum of Methanospirillum hungatei is Electrically Conductive

Here we report that the archaellum of Methanospirillum hungatei is electrically conductive. Our analysis of the previously published archaellum structure suggests that a core of tightly packed phenylalanines is one likely route for electron conductance. This is the first demonstration that electrically conductive protein filaments (e-PFs) have evolved in Archaea and is the first e-PF for which a structure is known, facilitating mechanistic evaluation of long-range electron transport in e-PFs.

microbiology↗