Town-scale microbial sewer community and H2S emissions response to common chemical and biological dosing treatments.

Controlling hydrogen sulfide (H2S) odors and emissions using a single, effective treatment across a town-scale sewer network is a challenge faced by many water utilities. Implementation of a sewer diversion provided the opportunity to compare the effectiveness of magnesium hydroxide (Mg(OH)2) and two biological dosing compounds (Bioproducts A and B), with different modes of action (MOA), in a field-test across a large sewer network. Mg(OH)2 increases sewer pH allowing suppression of H2S release into the sewer environment while Bioproduct A acts to disrupt microbial communication through quorum sensing (QS), reducing biofilm integrity. Bioproduct B reduces H2S odors by scouring the sewer of fats, oils and grease (FOGs), which provide adhesion points for the microbial biofilm. Results revealed that only Mg(OH)2 altered the microbial community structure and reduced H2S emissions in a live sewer system, whilst Bioproducts A and B did not reduce H2S emissions or have an observable effect on the composition of the microbial community at the dosed site. Study results recommend in situ testing of dosing treatments before implementation across an operational system.

Correction to: Enhanced Growth of Pilin-Deficient Geobacter sulfurreducens Mutants in Carbon Poor and Electron Donor Limiting Conditions.

The published version of this article contained an old version of Fig. 2.

Enhanced Growth of Pilin-Deficient Geobacter sulfurreducens Mutants in Carbon Poor and Electron Donor Limiting Conditions.

Geobacter sulfurreducens pili enable extracellular electron transfer and play a role in secretion of c-type cytochromes such as OmcZ. PilA-deficient mutants of G. sulfurreducens have previously been shown to accumulate cytochromes within their membranes. This cytochrome retaining phenotype allowed for enhanced growth of PilA-deficient mutants in electron donor and carbon-limited conditions where formate and fumarate are provided as the sole electron donor and acceptor with no supplementary carbon source. Conversely, wild-type G. sulfurreducens, which has normal secretion of cytochromes, has comparative limited growth in these conditions. This growth is further impeded for OmcZ-deficient and OmcS-deficient mutants. A PilB-deficient mutant which prevents pilin production but allows for secretion of OmcZ had moderate growth in these conditions, indicating a role for cytochrome localization to enabling survival in the electron donor and carbon-limited conditions. To determine which pathways enhanced growth using formate, Sequential Window Acquisition of all Theoretical Mass Spectra mass spectrometry (SWATH-MS) proteomics of formate adapted PilA-deficient mutants and acetate grown wild type was performed. PilA-deficient mutants had an overall decrease in tricarboxylic acid (TCA) cycle enzymes and significant upregulation of electron transport chain associated proteins including many c-type cytochromes and [NiFe]-hydrogenases. Whole genome sequencing of the mutants shows strong convergent evolution and emergence of genetic subpopulations during adaptation to growth on formate. The results described here suggest a role for membrane constrained c-type cytochromes to the enhancement of survival and growth in electron donor and carbon-limited conditions.

Growth of Caenorhabditis elegans in Defined Media Is Dependent on Presence of Particulate Matter.

Caenorhabditis elegans are typically cultured in a monoxenic medium consisting of live bacteria. However, this introduces a secondary organism to experiments, and restricts the manipulation of the nutritional environment. Due to the intricate link between genes and environment, greater control and understanding of nutritional factors are required to push the C. elegans field into new areas. For decades, attempts to develop a chemically defined, axenic medium as an alternative for culturing C. elegans have been made. However, the mechanism by which the filter feeder C. elegans obtains nutrients from these liquid media is not known. Using a fluorescence-activated cell sorting based approach, we demonstrate growth in all past axenic C. elegans media to be dependent on the presence of previously unknown particles. This particle requirement of C. elegans led to development of liposome-based, nanoparticle culturing that allows full control of nutrients delivered to C. elegans.