Assessing the microbiota of recycled bedding sand on a Wisconsin dairy farm

Background:Sand is often considered the preferred bedding material for dairy cows as it is thought to have lower bacterial counts than organic bedding materials and cows bedded on sand experience fewer cases of lameness and disease.Sand can also be efficiently recycled and reused,making it cost-effective.However,some studies have suggested that the residual organic material present in recycled sand can serve as a reservoir for commensal and pathogenic bacteria,although no studies have yet characterized the total bacterial community composition.Here we sought to characterize the bacterial community composition of a Wisconsin dairy farm bedding sand recycling system and its dynamics across several stages of the recycling process during both summer and winter using 16S rRNA gene amplicon sequencing.Results:Bacterial community compositions of the sand recycling system differed by both seasons and stage.Summer samples had higher richness and distinct community compositions,relative to winter samples.In both summer and winter samples,the diversity of recycled sand decreased with time drying in the recycling room.Compositionally,summer sand 14 d post-recycling was enriched in operational taxonomic units(OTUs)belonging to the genera Acinetobacter and Pseudomonas,relative to freshly washed sand and sand from cow pens.In contrast,no OTUs were found to be enriched in winter sand.The sand recycling system contained an overall core microbiota of 141 OTUs representing 68.45%±10.33%SD of the total bacterial relative abundance at each sampled stage.The 4 most abundant genera in this core microbiota included Acinetobacter,Psychrobacter,Corynebacterium,and Pseudomonas.Acinetobacter was present in greater abundance in summer samples,whereas Psychrobacter and Corynebacterium had higher relative abundances in winter samples.Pseudomonas had consistent relative abundances across both seasons.Conclusions:These findings highlight the potential of recycled bedding sand as a bacterial reservoir that warrants further study.

Transcription control engineering and applications in synthetic biology

In synthetic biology,researchers assemble biological components in new ways to produce systems with practical applications.One of these practical applications is control of the flow of genetic information(from nucleic acid to protein),a.k.a.gene regulation.Regulation is critical for optimizing protein(and therefore activity)levels and the subsequent levels of metabolites and other cellular properties.The central dogma of molecular biology posits that information flow commences with transcription,and accordingly,regulatory tools targeting transcription have received the most attention in synthetic biology.In this mini-review,we highlight many past successes and summarize the lessons learned in developing tools for controlling transcription.In particular,we focus on engineering studies where promoters and transcription terminators(cis-factors)were directly engineered and/or isolated from DNA libraries.We also review several well-characterized transcription regulators(trans-factors),giving examples of how cis-and trans-acting factors have been combined to create digital and analogue switches for regulating transcription in response to various signals.Last,we provide examples of how engineered transcription control systems have been used in metabolic engineering and more complicated genetic circuits.While most of our mini-review focuses on the well-characterized bacterium Escherichia coli,we also provide several examples of the use of transcription control engineering in non-model organisms.Similar approaches have been applied outside the bacterial kingdom indicating that the lessons learned from bacterial studies may be generalized for other organisms.