Ecology of zoophilic flies in livestock biocenoses of Ukraine

In modern animal husbandry of Ukraine, there are still some unresolved issues related to the high number of zoophilic flies in the territories of facilities and the spread of animal infectious and parasitic diseases. A detailed study of bioecological peculiarities of the dominant zoophilic fly species contributes to improving the effectiveness of measures to control ectoparasites. 27 zoophilic fly species have been found in animal breeding complexes. The maximum number of parasitic Diptera species was recorded on cattle-keeping premises. The biological properties of Neomyia cornicina (Fabricius, 1781) (size, shape, colour, duration of preimaginal phase development) were studied. Also, we studied the dynamics of the number and daily activity of dominant fly species (Musca domestica Linnaeus, 1758, M. autumnalis De Geer, 1776, Stomoxys calcitrans (Linnaeus, 1758)). When studying the intraspecies competition, a high-degree survival of M. domestica and M. autumnalis was determined in the conditions of critical nutritional deficiency (0.5 g of nutrient medium per larva) and increased density of individuals (the imago emergence was 38.6% and 34.0%, respectively). In similar maintenance conditions, the emergence of N. cornicina imago was low (14.6%). With a two-fold increase in the insectarium volume and in the amount of nutrient medium (1 g per larva), the imago emergence of M. domestica, M. autumnalis and N. cornicina increased to 64.0%, 39.2%, and 24.0%, respectively. With an even greater increase in the amount of nutrient medium (2 g per larva), the maximum emergence of imagoes of all the studied fly species was observed (M. domestica, M. autumnalis, and N. cornicina: 96.6%, 91.2% and 72.6%, respectively). In the conditions of interspecific competition, M. autumnalis suppressed N. cornicina even in conditions of a sufficient amount of nutrient substrate. In the competition between M. domestica and M. autumnalis, house fly dominated. Increasing the nutrient medium volume narrowed the gap between the competing species.

Diverse LXG toxin and antitoxin systems specifically mediate intraspecies competition in Bacillus subtilis biofilms

Biofilms are multispecies communities, in which bacteria constantly compete with one another for resources and niches. Bacteria produce many antibiotics and toxins for competition. However, since biofilm cells exhibit increased tolerance to antimicrobials, their roles in biofilms remain controversial. Here, we showed that Bacillus subtilis produces multiple diverse polymorphic toxins, called LXG toxins, that contain N-terminal LXG delivery domains and diverse C-terminal toxin domains. Each B. subtilis strain possesses a distinct set of LXG toxin–antitoxin genes, the number and variation of which is sufficient to distinguish each strain. The B. subtilis strain NCIB3610 possesses six LXG toxin–antitoxin operons on its chromosome, and five of the toxins functioned as DNase. In competition assays, deletion mutants of any of the six LXG toxin–antitoxin operons were outcompeted by the wild-type strain. This phenotype was suppressed when the antitoxins were ectopically expressed in the deletion mutants. The fitness defect of the mutants was only observed in solid media that supported biofilm formation. Biofilm matrix polymers, exopolysaccharides and TasA protein polymers were required for LXG toxin function. These results indicate that LXG toxin-antitoxin systems specifically mediate intercellular competition between B. subtilis strains in biofilms. Mutual antagonism between some LXG toxin producers drove the spatial segregation of two strains in a biofilm, indicating that LXG toxins not only mediate competition in biofilms, but may also help to avoid warfare between strains in biofilms. LXG toxins from strain NCIB3610 were effective against some natural isolates, and thus LXG toxin–antitoxin systems have ecological impact. B. subtilis possesses another polymorphic toxin, WapA. WapA had toxic effects under planktonic growth conditions but not under biofilm conditions because exopolysaccharides and TasA protein polymers inhibited WapA function. These results indicate that B. subtilis uses two types of polymorphic toxins for competition, depending on the growth mode.

Introgression dynamics from invasive pigs into wild boar following the March 2011 natural and anthropogenic disasters at Fukushima

Natural and anthropogenic disasters have the capability to cause sudden extrinsic environmental changes and long-lasting perturbations including invasive species, species expansion and influence evolution as selective pressures force adaption. Such disasters occurred on 11 March 2011, in Fukushima, Japan, when an earthquake, tsunami and meltdown of a nuclear power plant all drastically reformed anthropogenic land use. Using genetic data, we demonstrate how wild boar ( Sus scrofa leucomystax ) have persevered against these environmental changes, including an invasion of escaped domestic pigs ( Sus scrofa domesticus ). Concurrently, we show evidence of successful hybridization between pigs and native wild boar in this area; however in future offspring, the pig legacy has been diluted through time. We speculate that the range expansion dynamics inhibit long-term introgression and introgressed alleles will continue to decrease at each generation while only maternally inherited organelles will persist. Using the gene flow data among wild boar, we assume that offspring from hybrid lineages will continue dispersal north at low frequencies as climates warm. We conclude that future risks for wild boar in this area include intraspecies competition, revitalization of human-related disruptions and disease outbreaks.

A secondary metabolite drives intraspecies antagonism in a gut symbiont that is inhibited by peptidoglycan acetylation

The mammalian microbiome encodes numerous secondary metabolite biosynthetic gene clusters, yet their role in microbe-microbe interactions is unclear. Here, we characterized two polyketide synthase gene clusters (fun and pks) in the gut symbiont Limosilactobacillus reuteri. The pks, but not the fun cluster, encodes antimicrobial activity. Forty-one out of 51 L. reuteri strains tested are sensitive to Pks products, which was independent of strains host origin. The sensitivity to Pks was also established in intraspecies competition experiments in gnotobiotic mice. Comparative genome analyses between Pks-resistant and sensitive strains identified an acyltransferase gene (act) that is unique to Pks-resistant strains. Subsequent peptidoglycan analysis of the wild-type and the act mutant strains showed that Act acetylates peptidoglycan. The pks mutants lost their competitive advantage and act mutants lost their Pks resistance in vivo. Thus, our findings provide mechanistic insights into how closely related gut symbionts can compete and co-exist in the gastrointestinal tract.

Protection from Lethal Clostridioides difficile Infection via Intraspecies Competition for Cogerminant

ABSTRACT Clostridioides difficile, a Gram-positive, spore-forming bacterium, is the primary cause of infectious nosocomial diarrhea. Antibiotics are a major risk factor for C. difficile infection (CDI), as they disrupt the gut microbial community, enabling increased germination of spores and growth of vegetative C. difficile. To date, the only single-species bacterial preparation that has demonstrated efficacy in reducing recurrent CDI in humans is nontoxigenic C. difficile. Using multiple infection models, we determined that precolonization with a less virulent strain is sufficient to protect from challenge with a lethal strain of C. difficile, surprisingly even in the absence of adaptive immunity. Additionally, we showed that protection is dependent on high levels of colonization by the less virulent strain and that it is mediated by exclusion of the invading strain. Our results suggest that reduction of amino acids, specifically glycine following colonization by the first strain of C. difficile, is sufficient to decrease germination of the second strain, thereby limiting colonization by the lethal strain. IMPORTANCE Antibiotic-associated colitis is often caused by infection with the bacterium Clostridioides difficile. In this study, we found that reduction of the amino acid glycine by precolonization with a less virulent strain of C. difficile is sufficient to decrease germination of a second strain. This finding demonstrates that the axis of competition for nutrients can include multiple life stages. This work is important, as it is the first to identify a possible mechanism through which precolonization with C. difficile, a current clinical therapy, provides protection from reinfection. Furthermore, our work suggests that targeting nutrients utilized by all life stages could be an improved strategy for bacterial therapeutics that aim to restore colonization resistance in the gut.

Protection from lethal Clostridioides difficile infection via intraspecies competition for co-germinant

Clostridioides difficile, a Gram-positive, spore-forming bacterium, is the primary cause of infectious nosocomial diarrhea. Antibiotics are a major risk factor for C. difficile infection (CDI) as they disrupt the gut microbial community, enabling increased germination of spores and growth of vegetative C. difficile. To date the only single-species bacterial preparation that has demonstrated efficacy in reducing recurrent CDI in humans is non-toxigenic C. difficile. Using multiple infection models we determined that pre-colonization with a less virulent strain is sufficient to protect from challenge with a lethal strain of C. difficile, surprisingly even in the absence of adaptive immunity. Additionally, we showed that protection is dependent on high levels of colonization by the less virulent strain and that it is mediated by exclusion of the invading strain. Our results suggest that reduction of amino acids, specifically glycine following colonization by the first strain of C. difficile is sufficient to decrease germination of the second strain thereby limiting colonization by the lethal strain.

F-type Pyocins are Diverse Non-Contractile Phage Tail-Like Weapons for Killing Pseudomonas aeruginosa

ABSTRACTMost Pseudomonas aeruginosa strains produce bacteriocins derived from contractile or non-contractile phage tails known as R-type and F-type pyocins, respectively. These bacteriocins possess strain-specific bactericidal activity against P. aeruginosa and likely increase evolutionary fitness through intraspecies competition. R-type pyocins have been studied extensively and show promise as alternatives to antibiotics. Although they have similar therapeutic potential, experimental studies on F-type pyocins are limited. Here, we provide a bioinformatic and experimental investigation of F-type pyocins. We introduce a systematic naming scheme for genes found in R- and F-type pyocin operons and identify 15 genes invariably found in strains producing F-type pyocins. Five proteins encoded at the 3’-end of the F-type pyocin cluster are divergent in sequence, and likely determine bactericidal specificity. We use sequence similarities among these proteins to define 11 distinct F-type pyocin groups, five of which had not been previously described. The five genes encoding the variable proteins associate in two modules that have clearly re-assorted independently during the evolution of these operons. These proteins are considerably more diverse than the specificity-determining tail fibers of R-type pyocins, suggesting that F-type pyocins emerged earlier or have been subject to distinct evolutionary pressures. Experimental studies on six F-type pyocin groups show that each displays a distinct spectrum of bactericidal activity. This activity is strongly influenced by the lipopolysaccharide O-antigen type, but other factors also play a role. F-type pyocins appear to kill as efficiently as R-type pyocins. These studies set the stage for the development of F-type pyocins as anti-bacterial therapeutics.IMPORTANCEPseudomonas aeruginosa is an opportunistic pathogen that causes a broad spectrum of antibiotic resistant infections with high mortality rates, particularly in immunocompromised individuals and cystic fibrosis patients. Due to the increasing frequency of multidrug-resistant P. aeruginosa infections, there is great interest in the development of alternative therapeutics. One alternative is protein-based antimicrobials called bacteriocins, which are produced by one strain of bacteria to kill other strains. In this study, we investigate F-type pyocins, bacteriocins naturally produced by P. aeruginosa that resemble non-contractile phage tails. We show that they are potent killers of P. aeruginosa, and distinct pyocin groups display different killing specificities. We have identified the probable specificity determinants of F-type pyocins, which opens up the potential to engineer them to precisely target strains of pathogenic bacteria. The resemblance of F-type pyocins to well characterized phage tails will greatly facilitate their development into effective antibacterials.

A membrane-depolarizing toxin substrate of theStaphylococcus aureustype VII secretion system mediates intraspecies competition

The type VII protein secretion system (T7SS) is conserved acrossStaphylococcus aureusstrains and plays important roles in virulence and interbacterial competition. To date, only one T7SS substrate protein, encoded in a subset ofS. aureusgenomes, has been functionally characterized. Here, using an unbiased proteomic approach, we identify TspA as a further T7SS substrate. TspA is encoded distantly from the T7SS gene cluster and is found across allS. aureusstrains as well as inListeriaand Enterococci. Heterologous expression of TspA fromS. aureusstrain RN6390 indicates its C-terminal domain is toxic when targeted to theEscherichia coliperiplasm and that it depolarizes the cytoplasmic membrane. The membrane-depolarizing activity is alleviated by coproduction of the membrane-bound TsaI immunity protein, which is encoded adjacent totspAon theS. aureuschromosome. Using a zebrafish hindbrain ventricle infection model, we demonstrate that the T7SS of strain RN6390 promotes bacterial replication in vivo, and deletion oftspAleads to increased bacterial clearance. The toxin domain of TspA is highly polymorphic andS. aureusstrains encode multipletsaIhomologs at thetspAlocus, suggestive of additional roles in intraspecies competition. In agreement, we demonstrate TspA-dependent growth inhibition of RN6390 by strain COL in the zebrafish infection model that is alleviated by the presence of TsaI homologs.

Modelling ecosystem adaptation and dangerous rates of global warming

We are in a period of relatively rapid climate change. This poses challenges for individual species and threatens the ecosystem services that humanity relies upon. Temperature is a key stressor. In a warming climate, individual organisms may be able to shift their thermal optima through phenotypic plasticity. However, such plasticity is unlikely to be sufficient over the coming centuries. Resilience to warming will also depend on how fast the distribution of traits that define a species can adapt through other methods, in particular through redistribution of the abundance of variants within the population and through genetic evolution. In this paper, we use a simple theoretical ‘trait diffusion’ model to explore how the resilience of a given species to climate change depends on the initial trait diversity (biodiversity), the trait diffusion rate (mutation rate), and the lifetime of the organism. We estimate theoretical dangerous rates of continuous global warming that would exceed the ability of a species to adapt through trait diffusion, and therefore lead to a collapse in the overall productivity of the species. As the rate of adaptation through intraspecies competition and genetic evolution decreases with species lifetime, we find critical rates of change that also depend fundamentally on lifetime. Dangerous rates of warming vary from 1°C per lifetime (at low trait diffusion rate) to 8°C per lifetime (at high trait diffusion rate). We conclude that rapid climate change is liable to favour short-lived organisms (e.g. microbes) rather than longer-lived organisms (e.g. trees).