Effects of Advective-Diffusive Transport of Multiple Chemoattractants on Motility of Engineered Chemosensory Particles in Fluidic Environments.

Motility behavior of an engineered chemosensory particle (ECP) in fluidic environments is driven by its responses to chemical stimuli. One of the challenges to understanding such behaviors lies in tracking changes in chemical signal gradients of chemoattractants and ECP-fluid dynamics as the fluid is continuously disturbed by ECP motion. To address this challenge, we introduce a new multiscale numerical model to simulate chemotactic swimming of an ECP in confined fluidic environments by accounting for motility-induced disturbances in spatiotemporal chemoattractant distributions. The model accommodates advective-diffusive transport of unmixed chemoattractants, ECP-fluid hydrodynamics at the ECP-fluid interface, and spatiotemporal disturbances in the chemoattractant concentrations due to particle motion. Demonstrative simulations are presented with an ECP, mimicking Escherichia coli (E. coli) chemotaxis, released into initially quiescent fluids with different source configurations of the chemoattractants N-methyl-L-aspartate and L-serine. Simulations demonstrate that initial distributions and temporal evolution of chemoattractants and their release modes (instantaneous vs. continuous, point source vs. distributed) dictate time histories of chemotactic motility of an ECP. Chemotactic motility is shown to be largely determined by spatiotemporal variation in chemoattractant concentration gradients due to transient disturbances imposed by ECP-fluid hydrodynamics, an observation not captured in previous numerical studies that relied on static chemoattractant concentration fields.

Spatial Structure of the Mormon Cricket Gut Microbiome and its Predicted Contribution to Nutrition and Immune Function.

The gut microbiome of insects plays an important role in their ecology and evolution, participating in nutrient acquisition, immunity, and behavior. Microbial community structure within the gut is heavily influenced by differences among gut regions in morphology and physiology, which determine the niches available for microbes to colonize. We present a high-resolution analysis of the structure of the gut microbiome in the Mormon cricket Anabrus simplex, an insect known for its periodic outbreaks in the western United States and nutrition-dependent mating system. The Mormon cricket microbiome was dominated by 11 taxa from the Lactobacillaceae, Enterobacteriaceae, and Streptococcaceae. While most of these were represented in all gut regions, there were marked differences in their relative abundance, with lactic-acid bacteria (Lactobacillaceae) more common in the foregut and midgut and enteric (Enterobacteriaceae) bacteria more common in the hindgut. Differences in community structure were driven by variation in the relative prevalence of three groups: a Lactobacillus in the foregut, Pediococcus lactic-acid bacteria in the midgut, and Pantoea agglomerans, an enteric bacterium, in the hindgut. These taxa have been shown to have beneficial effects on their hosts in insects and other animals by improving nutrition, increasing resistance to pathogens, and modulating social behavior. Using PICRUSt to predict gene content from our 16S rRNA sequences, we found enzymes that participate in carbohydrate metabolism and pathogen defense in other orthopterans. These were predominately represented in the hindgut and midgut, the most important sites for nutrition and pathogen defense. Phylogenetic analysis of 16S rRNA sequences from cultured isolates indicated low levels of divergence from sequences derived from plants and other insects, suggesting that these bacteria are likely to be exchanged between Mormon crickets and the environment. Our study shows strong spatial variation in microbiome community structure, which influences predicted gene content and thus the potential of the microbiome to influence host function.

Productivity, carbon utilization, and energy content of mass in scalable microalgae systems.

This study was designed to examine carbon utilization within scalable microalgae production systems. Neochloris oleoabundans was produced in replicated troughs containing BG11 nutrient formulation. Atmospheric CO(2) was supplemented with ∼5% CO(2) or with NaHCO(3), and the pH of troughs receiving NaHCO(3) was adjusted with HCl or H(3)PO(4). Peak biomass concentrations reached 950, 1140, or 850 mg L(-1) and biomass productivities of 109, 96, and 74 mg L(-1) day(-1) were achieved in the CO(2), NaHCO(3):HCl and NaHCO(3):H(3)PO(4) troughs, respectively. The highest productivity is expected in a scaled-up continuous batch process of the CO(2) supplemented system, which was projected to yield 8948 L lipids ha(-1)yr(-1). Carbon utilization in the CO(2), NaHCO(3):HCl and NaHCO(3):H(3)PO(4) systems was ∼0.5, 15.5, and 12.9%, while the energy content of the combustible biomass was 26.7, 13.2, and 15.4 MJ kg(-1), respectively. Techno-economic analyses of microalgal production systems should consider efficiencies and cost-benefit of various carbon sources.

Biomass production and nutrient uptake by Neochloris oleoabundans in an open trough system.

The purpose of this paper is to present biomass and nutrient uptake data from Neochloris oleoabundans production in an open trough system. The growth medium used was BG11, temperature ranged from 16.7 °C to 25.3 °C, and pH ranged from 5.52 to 9.94 because the customary pH increase during algal biomass production was moderated by incoming CO(2) gas streams (atmospheric, 2%, 4%, and 6% CO(2)). Peak concentrations of algal biomass ranged from 643 to 970 mg L(-1), specific growth rates ranged from 0.15 to 0.37 day(-1), and doubling times ranged from 4.8 to 1.9 days. Carbon, nitrogen, and phosphorus were incorporated into the biomass at 0.05%, 8.3%, and 54% of supplied amounts. Open growth systems supplemented with CO(2) should be designed to regulate medium pH within the range of 6.3 to 7.1. Future research should examine various media and alternative carbon sources to decrease doubling times, increase peak concentrations, and optimize nutrient uptake.

Using student-generated UV-induced Escherichia coli mutants in a directed inquiry undergraduate genetics laboratory.

We report a thematic sequence of directed inquiry-based labs taking students from bacterial mutagenesis and phenotypic identification of their own self-created mutant, through identification of mutated genes by biochemical testing, to verification of mutant alleles by complementation, and finally to mutant allele characterization by DNA sequence analysis. The lab utilizes UV mutagenesis with wild-type Escherichia coli and a UV-sensitive isogenic derivative optimized for undergraduate use. The labs take advantage of the simplicity of E. coli in a realistic genetic investigation using safe UV irradiation methods for creation and characterization of novel mutants. Assessment data collected over three offerings of the course suggest that the labs, which combine original investigation in a scientifically realistic intellectual environment with learned techniques and concepts, were instrumental in improving students' learning in a number of areas. These include the development of critical thinking skills and understanding of concepts and methods. Student responses also suggest the labs were helpful in improving students' understanding of the scientific process as a rational series of experimental investigations and awareness of the interdisciplinary nature of scientific inquiry.

Characterization of gamma-butyrolactone autoregulatory signaling gene homologs in the angucyclinone polyketide WS5995B producer Streptomyces acidiscabies.

Organisms belonging to the genus Streptomyces produce numerous important secondary metabolites and undergo a sophisticated morphological differentiation program. In many instances these processes are under the control of gamma-butyrolactone (GBL) autoregulatory systems. Streptomyces acidiscabies strain 84.104 produces the secondary metabolite aromatic angucyclinone polyketide WS5995B. In order to explore the role of GBL regulatory circuitry in WS5995B production and morphogenesis in S. acidiscabies, a gene cluster encoding GBL autoregulatory signaling homologs was identified and characterized. Two GBL receptor homologs, sabR and sabS, were found flanking a GBL synthase homolog sabA. Strains carrying mutations in sabS produced elevated levels of WS5995B and displayed conditional morphological defects reminiscent of defects seen in Streptomyces bldA mutants. Notably, sabS possesses a TTA codon predicted to be recognized by tRNA(leu). sabA mutants produced higher levels of WS5995B than the wild-type strain but to a lesser extent than the levels of WS5995B seen in sabS mutants. Purified recombinant SabR and SabS were tested for their abilities to bind predicted AT-rich autoregulatory element (ARE) boxes within the sabRAS region. SabS did not bind any DNA sequences in this region, while SabR bound an ARE box in the region upstream of sabS. Quantitative reverse transcription-PCR analysis revealed higher levels of sabS transcript in sabR mutants than in the wild-type strain, suggesting that sabS expression is repressed by SabR. Based on these data, we propose that the S. acidiscabies sabRAS genes encode components of a signaling pathway which participates in the regulation of WS5995B production and morphogenesis.