Healy, F. | bioRxiv Science

bioRxiv2025

Effects of ΔmotY mutations on motility behavior of Pseudomonas aeruginosa chimeric periplasmic stator variants

Pseudomonas aeruginosa utilizes dual flagellar stator systems for motility; and dual stator bacteria possess auxiliary flagellar rotor ring components in their periplasm. In P. aeruginosa MotAB and MotCD comprise the dual stator system and MotY is the auxiliary periplasmic ring component. We investigated motility of strains and their isogenic {Delta}motY derivatives which expressed chimeric MotB/MotD periplasmic domains and characterized differences in motility behaviors. We found in general motility is severely impaired in strains carrying motY deletions and which express C-terminal periplasmic regions of MotD, compared with strains expressing MotB C-terminal counterparts. Motility in soft agar is slightly increased in strains expressing N-terminal MotB transmembrane domains and MotD C-terminal periplasmic plug, PGB, and extensions, but motility is severely impaired in {Delta}motY strains. Addition of the extended 24-residue C-terminus of MotB to the C-terminus of MotD does not significantly affect either motility or compensate for the deleterious effect of {Delta}motY mutation, but does significantly increase motility in motY+ backgrounds. The soft agar motility results for organisms with wild type MotAB stators was not different from those with MotAB stators carrying 24 residue MotB C-terminal deletions; however, motility of these mutants was significantly lower in {Delta}motY mutants compared to {Delta}motY mutants expressing wild type MotAB stators. We discuss contributions of stator functional domains to motility and the effects of {Delta}motY deletion. Lastly, we speculate on possible mechanistic roles for the two stator plug types based on thermodynamic considerations related to differences in composition of the hydrophobic surfaces of the two amphipathic helices. IMPORTANCEPseudomonas aeruginosa uses two torque-generating stators, MotAB and MotCD, to drive flagellar rotation. Dual stator bacteria have additional rotor components; in P. aeruginosa, this component has been identified as MotY. This study investigates the interaction between the C-terminal plug and periplasmic regions of the MotB and MotD components of the MotAB and MotCD stator complexes with MotY. Motility assays of periplasmic chimeric strains expressing variants with MotB and MotD C-terminal plug and peptidoglycan binding domains reveal an enhanced sensitivity of MotD C-terminus to MotY deletions. These data suggest that critical interactions, either direct or indirect, must take place between the basal body MotY ring complex and MotD periplasmic regions for proper function of the MotCD stator in flagellar motility.

microbiology↗

bioRxiv2016

Structure and culture of the gut microbiome of the Mormon cricket Anabrus simplex

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 thought to be 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 eleven bacterial phylotypes from the Lactobacillaceae, Enterobacteriaceae, and Streptococcaeae. 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 phylotype 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. 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 provides the foundation for future work on an economically important insect and emerging model for the study of how social interaction influence host-microbe symbiosis.

microbiology↗