Biology subjects

Hill, P. J.

Publications and source records attributed to Hill, P. J..

3 recordsLinked to original sources

bioRxiv2022

Engineering Nanowires in Bacteria to Elucidate Electron Transport Structural Functional Relationships

Bacterial pilin nanowires are protein complexes, suggested to possess electroactive capabilities forming part of the cells bioenergetic programming. Their role is thought to be linked to facilitating electron transfer with the external environment to permit metabolism and cell-to-cell communication. There is a significant debate, with varying hypotheses as to the nature of the proteins currently lying between type-IV pilin-based nanowires and polymerised cytochrome-based filaments. Importantly, to date, there is a very limited structure-function analysis of these structures within whole bacteria. In this work, we engineered Cupriavidus necator H16, a model autotrophic organism to express differing aromatic modifications of type-IV pilus proteins to establish structure-function relationships on conductivity and the effects this has on pili structure. This was achieved via a combination of high-resolution PeakForce tunnelling atomic force microscopy (PeakForce TUNA) technology, alongside conventional electrochemical approaches enabling the elucidation of conductive nanowires emanating from whole bacterial cells for the first time. This work is the first example of functional type-IV pili protein nanowires produced under aerobic conditions using a CN chassis. This work has far-reaching consequences in understanding the basis of bio-electrical communication between cells and with their external environment. O_FIG O_LINKSMALLFIG WIDTH=182 HEIGHT=200 SRC="FIGDIR/small/510814v2_ufig1.gif" ALT="Figure 1"> View larger version (90K): org.highwire.dtl.DTLVardef@134d026org.highwire.dtl.DTLVardef@4d84f3org.highwire.dtl.DTLVardef@15379fcorg.highwire.dtl.DTLVardef@16d942c_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstract displaying theoretical PilA monomer models (left), PeakForce TUNA atomic force microscopy contact current images (right) of wild-type (top) and modified with increased tyrosine content (bottom) PilA filaments expressed by Cupriavidus necator H16 cells.

bioengineering↗

bioRxiv2022

Distinct types of multicellular aggregates in Pseudomonas aeruginosa liquid cultures

Pseudomonas aeruginosa forms suspended multicellular aggregates when cultured in liquid media. Such aggregates may be important in disease, and/or as a pathway to biofilm formation. The polysaccharide Psl and extracellular DNA (eDNA) have both been implicated in aggregation, but previous results depend strongly on the experimental conditions. Here we develop a quantitative microscopy-based method for assessing changes in the size distribution of suspended aggregates over time in growing cultures. For exponentially growing cultures of P. aeruginosa PAO1, we find that aggregation is mediated by cell-associated Psl, rather than by either eDNA or se-creted Psl. These aggregates arise de novo within the culture via a growth process that involves both collisions and clonal growth. They are "non-cheatable" since Psl non-producing cells do not aggregate with producers. In contrast, we find that stationary phase (overnight) cultures contain a different type of multicelullar aggregate, in which both eDNA and Psl mediate cohesion. Our findings suggest that the physical and bi-ological properties of multicellular aggregates may be very different in early-stage vs late-stage bacterial cultures.

microbiology↗

bioRxiv2017

Reconstructing Promoter Activity From Lux Bioluminescent Reporters

The bacterial Lux system is used as a gene expression reporter. It is fast, sensitive and non-destructive, enabling high frequency measurements. Originally developed for bacterial cells, it has been adapted for eukaryotic cells, and can be used for whole cell biosensors, or in real time with live animals without the need for slaughter. However, correct interpretation of bioluminescent data is limited: the bioluminescence is different from gene expression because of nonlinear molecular and enzyme dynamics of the Lux system. We have developed a modelling approach that, for the first time, allows users of Lux assays to infer gene transcription levels from the light output. We show examples where a decrease in bioluminescence would be better interpreted as a switching off of the promoter, or where an increase in bioluminescence would be better interpreted as a longer period of gene expression. This approach could benefit all users of Lux technology.

bioinformatics↗