Competitive Exclusion Research Articles

Forest management scenarios drive future dynamics of Mediterranean planted pine forests under climate change

ContextPlanted pine forests are highly abundant communities in the Mediterranean Basin. Being the result of past reforestation, these forests show high species and structural homogeneity. Diversification to conifer-broadleaved mixed forests is recommended to promote adaptation to climate change and increase their resilience to perturbations.ObjectivesThis study aims at evaluating how these planted pine forests will develop in the future as a result of the combined impacts of management and climate.MethodsWe applied a forest landscape model (LANDIS-II) to simulate different climate scenarios and management strategies designed in cooperation with forest managers to assess their effects on the performance of planted pine forests and their change in terms of forest composition.ResultsClimate change scenarios caused a shift in the phenological growth pattern of planted pine forests by reducing forest growth during summer and increasing photosynthetic productivity in spring and fall, particularly under high emission scenarios. Biomass increased through time and more strongly under climate change, but this increase differs among species, resulting in changes of forest types across the landscape. Our results portray natural succession as the main driver of forest change, but intensive management accelerated this process by limiting pine growth and promoting growth of oak species.ConclusionsOur results highlight the importance of active management on planted pine forests to favour mixed and climate-adapted ecosystems in shorter time scales than offered by succession alone. Moreover, our spatially explicit modelling approach helps to identify areas where lack of seed dispersal and/or competitive exclusion prevent natural diversification, providing useful recommendations for interventions. However, the modelling approach has some limitations since it does not consider natural disturbances.Graphical abstract

Comparative genetic study of the colony structure and colony spatial distribution between the higher termite Amitermes parvulus and the lower, subterranean termite Reticulitermes flavipes in an urban environment

In insects, ecological competition has often resulted in phenotypic changes and modifications to foraging areas. In termites—and social insects as a whole—colonies cannot easily escape competition through the relocation of their colony. In these species, the outcomes of inter and intra-specific competition are influenced by different life history traits, such as colony size, breeding system (number and types of reproductives), food preference, tunneling patterns, nest site selection, and antagonism between colonies. Here, we investigated variation in breeding system and spatial distribution among colonies of a higher termite Amitermes parvulus and a subterranean termite Reticulitermes flavipes within an urban landscape. We first developed microsatellite markers as a tool to study these life history traits in A. parvulus. Second, we assessed competitive exclusion or tolerance of A. parvulus and R. flavipes colonies by determining their fine-scale distribution using monitoring stations on a grid site, and their large-scale distribution across an urban landscape. Third, we investigated the breeding system of A. parvulus colonies. We showed that the numerous colonies of R. flavipes inhabiting a restricted area contrast with the few, but spatially expansive colonies of A. parvulus, suggesting these species face different degrees of intra-specific competition. We showed that colonies of A. parvulus frequently merged together, and all of them were likely headed by inbred neotenic reproductives, two characteristics rarely observed in higher termites. Overall, our study revealed drastic differences in colony structure, breeding systems and foraging ranges between the two species. These differences may reflect differences in food preference and food availability between the two species allowing their co-existence within the same urban environment.

Coexistence and Replacement of Two Different Maturation Strategies Adopted by a Stage-Structured Population

Maturation strategies play a key role in the survival and development of populations. In response to changes in the external environment and human interventions, populations adopt appropriate maturation strategies. Different maturation strategies can lead to different birth and mortality rates. In this paper, we develop and analyze a stage-structured population model with two maturation strategies to obtain conditions for the coexistence of two maturation strategies and conditions for competitive exclusion. Our results also show that equality of fitness—represented by basic reproductive numbers being greater than 1 under different maturation strategies—promotes the coexistence of the two strategies. The reason why a strategy is replaced by another one is that the population adopting this strategy has weak fitness, which is measured by the basic reproductive number.

Grazing alters the relationships between species diversity and biomass during community succession in a semiarid grassland

The relationships between biodiversity and ecosystem functions (BEF) are crucial for ecosystem management. However, little is known about how grazing affects BEF relationships in the context of ecological succession. Here, using a 5-year experiment in a semiarid grassland of the Loess Plateau, China, we mainly focused on how grazing affected the relationships between plant species diversity and aboveground biomass (AGB) and explored the underlying mechanisms behind the relationships. In addition, we compared the plant dynamics of community composition and structure under no-grazing and grazing treatments during succession. We found that the plant species diversity-AGB relationship shifted from a negative-linear pattern in no-grazing to a humped-back model in grazing during plant community succession, suggesting that grazing could regulate dominant species and alter the availability of light resources to suppress competitive exclusion during succession. In addition, changes in annual plants over time played crucial roles in the BEF relationships. The increase in annual Salsola collina in this study, which also alters multiple mechanisms of plant interaction, had a significant effect on the negative-linear relationship both with and without grazing. On average, compared to no-grazing treatment, grazing significantly decreased the plant community density (39.53 %), cover (16.97 %), height (7.85 %), and AGB (9.35 %), but increased plant diversity, including species richness and the Shannon–Wiener index, and especially dramatically enhanced the Shannon–Wiener index (ranging from 1.55 to 2.13). These results underline the close association between grazing and the dynamics of plant communities in semiarid grasslands during succession. In particular, our findings further reveal grazing-dependent relationships between diversity and AGB, which have significant implications for the management and biodiversity conservation measures of semiarid grassland ecosystems.

Emerging niche clustering results from both competition and predation.

Understanding species coexistence has been a central question in ecology for decades, and the notion that competing species need to differ in their ecological niche for stable coexistence has dominated. Recent theoretical and empirical work suggests differently. Species can also escape competitive exclusion by being similar, leading to clusters of species with similar traits. This theory has so far only been explored under competition. By combining mathematical and numerical analyses, we reveal that competition and predation are equally capable to promote clusters of similar species in prey-predator communities, their relative importance being modulated by resource availability. We further show that predation has a stabilizing effect on clustering patterns, making the clusters more diverse. Our results merge different ecological theories and bring new light to the emergent neutrality theory by adding the perspective of trophic interactions. These results open new perspectives to the study of trait distributions in ecological interaction networks.

Assembly of understory woody communities during the close-to-nature restoration of a Pinus massoniana lamb. plantation in the southern subtropical region of China: From environmental filtering to competitive exclusion

In Pinus massoniana Lamb. plantations, the understory plant community has a major role in close-to-nature restoration. However, investigations of the processes that create and maintain understory plant community assemblages on plantations are relatively rare. In this study, we used the method of space instead of time to study the assembly methods of woody communities at different strata in the subtropical P. massoniana plantation in China, in an attempt to discover the driving force of plantation community assembly. We found that soil water content, soil organic matter, and soil temperature were key environmental factors affecting community species composition across strata. The evolution of plant leaf traits was conserved in the shrub stratum and convergent in the tree stratum. While the nearest taxon index (NTI) of plant leaf traits did not change significantly as the close-to-nature restoration progressed, NTI did generally trend towards being dispersed. The phylogeny NTI in the shrub stratum decreased, meaning the community changed from clustered to dispersed. In the tree stratum on the other hand, an increasing phylogeny NTI meant the community changed from dispersed to clustered. Although the aggregation patterns of shrub and tree communities were opposite, the driving force of community assembly was the same, shifting from environmental filtration to competitive exclusion.

Non-Aflatoxigenic Aspergillus flavus: A Promising Biological Control Agent against Aflatoxin Contamination of Corn.

Aflatoxins (AFs) are a family of mycotoxins produced by molds in agricultural products. To deal with this problem, one of the control methods is the biological solution using a non-pathogenic strain Aspergillus flavus NRRL 21882 (Afla-Guard). This study was conducted to evaluate the potential of A. flavus NRRL 21882 to control the AF contamination of corn in the field and during storage in 2018 and 2019. The experimental design consists of treatment at different vegetative stages of infested corn in the field trial. After the field has been harvested, half the corn kernels from both treated and control plots were treated with biopesticide; the other half of the kernels from each group were not treated and used as the control of the storage. Consequently, storage applications consisted of kernels: (1) not treated at all; (2) treated prior to storage; (3) field-treated; and (4) treated both in the field and prior to storage. After field trials, the AF content was very low in the treated plots, ranging from 0.50 to 1.04 μg/kg and from 0.50 to 0.73 μg/kg in 2018 and 2019, respectively, while the AF content in the control was 98.3 and 73.9 μg/kg in 2018 and 2019, respectively. After storage, corn kernels from field plots that were treated with the biopesticide (treated/control) showed low levels of AFs, even after they have been stored under conditions conducive to AF contamination. The biopesticide effect ranged from 98 to 99% and from 69 to 99% in the field and during storage, respectively. This paper has provided the first indications on AF biocontrol based on a competitive exclusion in the corn-growing region of Turkey. The data showed that spraying during the storage period did not provide any further prevention of AF contamination, and only treatment in the field had a significant effect on AFs that occurred in storage.

Critical Optical Depth Hypothesis for Phytoplankton Growth and Bloom. A New Graphical Approach to the Classic Sverdrup Critical Depth Model

A modification to the classic Sverdrup Critical Depth Model relating phytoplankton light-limited net growth in a mixed water column to its depth is presented by introducing optical depth in place of the physical depth of the column, as well as by the inclusion of self-shading and competition among phytoplankton species for light. The concept of critical optical depth of a well-mixed column is used to establish criteria for phytoplankton growth and competitive exclusion. This model shows not only the direction of the growth for a given column, such as the classic Sverdrup model, but also the magnitude of that growth. The model relies on plots of the average specific (per unit biomass) rate of this growth in the column against the optical depth of that column. These graphs are invariant under changes of light absorbers in the column as well as the depth of the column. In particular, these graphs do not change in the presence of competing species or with changes in column biomass, thus facilitating the analysis of these processes. Also, for this purpose, the concept of opacity load is introduced to name the optical depth. Such an extended Sverdrup model provides a simple visual, qualitative way of obtaining results consistent with Huisman and Weissing’s (1994) critical light theory. It is convenient for considering more complex phytoplankton growth scenarios.

Role of the microbiota in oncogenesis

Objective. To conduct a systematic analysis of data on the results of studies published in scientific journals on the pro-carcinogenic and anticarcinogenic role of microbiota, as well as on the therapeutic potential of microorganisms in oncogenesis.Material and Methods. The articles were searched using the Web of Science, Scopus, PubMed, Medline, and eLIBRARY databases. More than 150 sources dedicated to the study of the carcinogenic function of the microbiota and the possible influence of its species and quantitative composition on the efficacy and toxicity of antitumor therapy were found. Data from 71 articles were included in the review.Results. The relationship between the gut microbiota and cancer is multifactorial and bilateral: pro-carcinogenic on the one hand and anti-carcinogenic on the other hand. Microorganisms can induce tumor growth and cancer development through DNA damage and induction of mutagenesis, trigger oncogenic signals, disruption of barrier function, as well as immune response system disruption. Depletion of microbiota, the development of dysbiosis and induction of chronic inflammatory state are negative factors in the development of cancer. The anticancer effect of microorganisms is presumably based on the production of tumor-suppressive metabolites that function through multiple immune reactions. Maintenance of barrier function, competitive exclusion of pathogenic bacteria, and direct action on immune cells to prevent inflammation are also important protective factors. The presence of intratumor microorganisms in various tumors has been noted. Changes in species and quantitative composition of cancer patients’ microbiota are influenced by diet, taking antibacterial drugs, chemo-, immuno- and radiation therapy. In turn, the microbiota can affect the ongoing treatment. Numerous studies on the influence of the gut microbiota on the efficacy of immunotherapy, particularly in disseminated melanoma, have been conducted. It has been suggested that primary resistance to immunotherapy may be related to the abnormal composition of the gut microbiota. The level of gut microfora composition diversity and the number of Faecalibacterium or Bacteroidales in the fecal microbiota have been suggested to be the predictor of response to anti-PD-1 therapy. To change the composition and activity of the gut microbiota, several therapeutic methods, such as the administration of prebiotics, probiotics, synbiotics, postbiotics, fecal microbiota transplantation, as well as the change in the microbiota composition through a specific diet, are available.

Host filtering, not competitive exclusion, may be the main driver of arbuscular mycorrhizal fungal community assembly under high phosphorus

Abstract A major goal in ecology is understanding the factors which determine the diversity and distribution of organisms. The outcome of the symbiotic relationship between plants and arbuscular mycorrhizal (AM) fungi is strongly influenced by soil phosphorus (P) availability. Despite this knowledge, there is still much to uncover about how soil P status can shape the taxonomic and phylogenetic assembly of root‐colonising AM fungi. Additionally, there is a paucity of understanding about the implications of these changes for the outcome of the AM symbiosis in terms of plant growth, nutrient status and defence traits. We conducted a factorial pot experiment where sorghum (Sorghum bicolor) was grown under three different P treatments (low, medium and high), in the presence or absence of a natural AM fungal community. By analysing the diversity and community structure of the fungal community colonising roots, we aimed to determine if and how soil P influences the relatedness of these communities and whether competitive exclusion or environmental filtering play a more significant role in their assembly. Additionally, we evaluated the concomitant outcomes for plant growth, nutrient acquisition and defensive chemistry (phenolics). Increasing P availability reduced AM fungal richness and increased community evenness. Root‐colonising AM fungal communities under the high P treatment had significantly reduced phylogenetic diversity and comparatively lower mean pairwise distances among all treatments. This indicated that AM fungal communities became more closely related (phylogenetically clustered) with increasing soil P. The mycorrhizal growth and mycorrhizal P responses of plants were positive under low and medium P, but this was lost under high P, however, plant phenolics were increased. Our results suggest that under high P conditions, environmental filtering plays an important role in AM fungal community assembly as host plants alter their selectivity of fungal functional groups prioritising those associated with enhancing plant stress resistance and defences, rather than nutrient acquisition. Here we demonstrated how soil P status can shape taxonomic and phylogenetic assembly of AM fungi and the associated functional outcomes for the host. Read the free Plain Language Summary for this article on the Journal blog.

A Reaction–Diffusion–Advection Chemostat Model in a Flowing Habitat: Mathematical Analysis and Numerical Simulations

This paper is concerned with a reaction–diffusion–advection chemostat model with two species growing and competing for a single-limited resource. By taking the growth rates of the two species as variable parameters, we study the effect of growth rates on the dynamics of this system. It is found that there exist several critical curves, which may classify the dynamics of this system into three scenarios: (1) extinction of both species; (2) competitive exclusion; (3) coexistence. Moreover, we take numerical approaches to further understand the potential behaviors of the above critical curves and observe that the bistable phenomenon can occur, besides competitive exclusion and coexistence. To further study the effect of advection and diffusion on the dynamics of this system, we present the bifurcation diagrams of positive equilibrium solutions of the single species model and the two-species model with the advection rates and the diffusion rates increasing, respectively. These numerical results indicate that advection and diffusion play a key role in determining the dynamics of two species competing in a flow reactor.

On a competition model in stream environments: The effects of seasonal pulses and advection

A diffusion-advection competition model with different pulses has been investigated in order to understand how the impulsive intervention affects the dynamics and alters the competition state of two competitors in open advective environments. The threshold values are introduced as the principal eigenvalues of the periodic problems with pulses and defined by the spectral radius of a time-T map. We have obtained two critical advection curves depending on pulses that determine the stability of the periodic steady states and have computed these numerically. The dynamics of two competitors in open advective environments such as competition exclusion, co-extinction, coexistence and bistability have been classified. By applying different impulsive effects, simulation analysis shows interesting scenarios, and reveals that a tradeoff between two different impulsive interventions and movements can be found in order to improve sustainable ecological development and economic benefits.

Contrasting patterns along tall grass dominance in mowed mountain grasslands

Semi-natural grasslands are a perfect system to study how biotic interactions influence coexistence thanks to their high species diversity in small areas resulting from millennia of anthropogenic management. Management cessation led to the increase of highly competitive tall-perennial tussock species with a marked drop of taxonomical (TD) and functional diversity (FD). The effect of highly competitive tall-perennial tussock species on plant community under management condition is largely understudied. In this study, we try to shed light on the effect of Brachypodium genuense which dominates sub-Mediterranean abandoned mountain grasslands TD and FD. For FD, we selected as traits plant height (H), specific leaf area (SLA) and leaf area (LA). We hypothesized i) TD decreases as the cover of B. genuense increases; ii): H converges towards higher values resulting from weaker competitive exclusion; iii) SLA and LA diverge resulting from limiting similarity. TD and FD were calculated using Rao's Quadratic Entropy. We computed the community weighted mean (CWM) that we analysed with fourth corner approach and built linear models using B. genuense as a predictor. We found that B. genuense ability in dominating the grassland plant community is altered by mowing in two different ways. On one hand, increase of B. genuense lead to a drop in TD whereas for FD the increase showed contrasting patterns with divergence for H and convergence for SLA. On the other, there were changes in the main dominant strategies with an overall increase in mean trait values of both H and SLA indicating species taller in size and more fast-growing. Overall, our results highlighted how tall-perennial tussock species under mowing conditions lead to a more stratified plant community convergent towards resource acquisition strategies. A multifaceted approach should be adopted to have a better understanding of the biotic drivers on different aspect of plant community.

Osteohistology of the large-sized Cretaceous crocodylomorph Stratiotosuchus maxhechti (Notosuchia, Baurusuchidae) indicates fast growth and niche partitioning with medium-sized theropods

Among the wide diversity of notosuchian crocodyliforms, Baurusuchidae is remarkable by their morphology, indicating a terrestrial hypercarnivory habit during the Late Cretaceous of Gondwana. Commonly, amongst baurusuchids, the anatomy of the large-sized Stratiotosuchus maxhechti shows theropod mimic features in its skull and limb bones. Such similarities supported the hypothesis of competitive exclusion of medium to large-sized theropods by baurusuchids. However, a recent taphonomical approach claims that other lines of evidence should be considered (e.g., biomechanics); due to the biased fossil record found in the Bauru Group. This approach supported niche partitioning between theropods and baurusuchids instead of competitive exclusion. Here we performed a paleohistological analysis on a baurusuchid (S. maxhechti) to evaluate if the terrestrial ecology implies fast growth and if the microstructure is similar to what is found in theropods, with insights into a niche competition hypothesis. The samples were taken from one specimen with two femora and another one comprising the left ulna and tibia. All the four samples show the presence of fibrolamellar bone complex arranged in a cyclical growth. The growth zones are composed of woven matrix that gradually turns into a parallel-fibered bone, and is followed by lines of arrested growth (LAGs). There is also the presence of simple and anastomosed vascular canals. Compared to living crocodylians the growth shows a higher depositional rate and a more complex organization pattern. In this respect, the growth dynamics are like medium-to-large theropods. Stratiotosuchus lacks an External Fundamental System (EFS), which indicates that the material studied here represents individuals that died before reaching their maximum size, suggesting that they could take more than twelve years to to be fully grown. Comparing the body mass estimates by femoral circumference (∼178–180 kg) and the bone microstructure with theropods, they share a fast growth pattern by showing fibrolamellar bone complex. However, the body size diversity in both groups favors the niche partitioning hypothesis over the suggestion of competitive exclusion between baurusuchids and theropods.

Simultaneous competition and environmental filtering in woody communities of the understory of Eucalyptus plantations in the Cerrado

Dense and species-rich understory communities have been commonly found in old or abandoned stands of Eucalyptus plantations in the Cerrado domain presenting plant species and ecological niches that suggest a repository of the original biodiversity. This repository depends on the largely unknown effect of Eucalyptus plantations on their understories. We addressed this issue by testing if the effect of Eucalyptus trees on the assembly of Cerrado communities causes environmental filtering or competitive exclusion. For the test, 40 plots (20 inside stands and 20 outside) were allocated and all woody plants with a circumference at the ground level equal to or greater than 10 cm were sampled. Species richness, diversity indexes and species turnover were determined. The phylogenetic structure was evaluated at different scales using the values of Mean Pairwise Distance (MPD), the Mean Nearest Taxon Distance (MNTD), the Net Relatedness Index (NRI) and the Nearest Taxon Index (NTI), as well as phylobetadiversity indices. The metrics of alpha and beta phylogenetic diversity (NTI, MNTD, NRI and MPD, betaMPD and betaMNTD) fell within the random expectation in each plant community, suggesting a phylogenetic uniformity, but fewer plants of the Fabaceae family than expected by chance were detected outside Eucalyptus stands suggesting that this family is filtered in inside Eucalyptus stands. Species richness is lower inside than outside Eucalyptus stands. The pattern is congruent with simultaneous environmental filtering and competitive exclusion in a context of niche conservatism which means that functional traits are conserved within phylogenetic lineages.

Recent Trends on Mitigative Effect of Probiotics on Oxidative-Stress-Induced Gut Dysfunction in Broilers under Necrotic Enteritis Challenge: A Review.

Gut health includes normal intestinal physiology, complete intestinal epithelial barrier, efficient immune response, sustained inflammatory balance, healthy microbiota, high nutrient absorption efficiency, nutrient metabolism, and energy balance. One of the diseases that causes severe economic losses to farmers is necrotic enteritis, which occurs primarily in the gut and is associated with high mortality rate. Necrotic enteritis (NE) primarily damages the intestinal mucosa, thereby inducing intestinal inflammation and high immune response which diverts nutrients and energy needed for growth to response mediated effects. In the era of antibiotic ban, dietary interventions like microbial therapy (probiotics) to reduce inflammation, paracellular permeability, and promote gut homeostasis may be the best way to reduce broiler production losses. The current review highlights the severity effects of NE; intestinal inflammation, gut lesions, alteration of gut microbiota balance, cell apoptosis, reduced growth performance, and death. These negative effects are consequences of; disrupted intestinal barrier function and villi development, altered expression of tight junction proteins and protein structure, increased translocation of endotoxins and excessive stimulation of proinflammatory cytokines. We further explored the mechanisms by which probiotics mitigate NE challenge and restore the gut integrity of birds under disease stress; synthesis of metabolites and bacteriocins, competitive exclusion of pathogens, upregulation of tight junction proteins and adhesion molecules, increased secretion of intestinal secretory immunoglobulins and enzymes, reduction in pro-inflammatory cytokines and immune response and the increased production of anti-inflammatory cytokines and immune boost via the modulation of the TLR/NF-ĸ pathway. Furthermore, increased beneficial microbes in the gut microbiome improve nutrient utilization, host immunity, and energy metabolism. Probiotics along with biosecurity measures could mitigate the adverse effects of NE in broiler production.

SYNBIO® Probiotic and Antioxidant Dietary Supplementation: Clinical Trial Evaluation of Potential Effects on Airline Flight Crew Members' Well-Being.

The irregular lifestyle of airline crew members, wide/adverse job-related exposures, and the impact of temporary hypoxia on gut microbiota well-being have increased concern about the daily recommended dose of certain nutrients among flight crew. The aim of this study was to determine if daily consumption of a SYNBIO® probiotics-elderberry extract supplement (ACTIVE) may contribute to the well-being of flight attendants. Forty healthy crew members enrolled in a double-blind, randomized, placebo-controlled study consumed one ACTIVE capsule/day or placebo for 30 days. Bowel well-being, health-related quality of life, and gastrointestinal tolerance were assessed by validated questionnaires. Saliva and fecal samples were analyzed to determine secretory immunoglobulin-A (sIgA) levels and to characterize gut microbiota composition, respectively. ACTIVE subjects presented a physiological improvement and a statistically significant higher Psychological General Well-Being Index (PGWBI) global score compared to PLACEBO subjects. The ACTIVE subjects showed significantly increased levels of lactobacilli and bifidobacteria compared to the PLACEBO group, while a significant increase in lactobacilli and a significant reduction in Enterobacteriaceae were registered when compared with the beginning of supplementation, confirming the persistence of probiotics in the gastrointestinal tract and the direct antagonism and competitive exclusion effects. Additionally, sIgA levels were significantly higher in the ACTIVE group compared to the baseline and to the PLACEBO group at the end of supplementation. The ACTIVE supplementation might be beneficial to airline crew members, improving their physiological state, their immune defenses, and the strength and efficiency of their gastrointestinal tract when responding to stressful conditions.

Competitive exclusion principle among synthetic non-biochemical protocells

Competitive exclusion principle among synthetic non-biochemical protocells

Potential Use of a Combined Bacteriophage-Probiotic Sanitation System to Control Microbial Contamination and AMR in Healthcare Settings: A Pre-Post Intervention Study.

Microbial contamination in the hospital environment is a major concern for public health, since it significantly contributes to the onset of healthcare-associated infections (HAIs), which are further complicated by the alarming level of antimicrobial resistance (AMR) of HAI-associated pathogens. Chemical disinfection to control bioburden has a temporary effect and can favor the selection of resistant pathogens, as observed during the COVID-19 pandemic. Instead, probiotic-based sanitation (probiotic cleaning hygiene system, PCHS) was reported to stably abate pathogens, AMR, and HAIs. PCHS action is not rapid nor specific, being based on competitive exclusion, but the addition of lytic bacteriophages that quickly and specifically kill selected bacteria was shown to improve PCHS effectiveness. This study aimed to investigate the effect of such combined probiotic-phage sanitation (PCHSφ) in two Italian hospitals, targeting staphylococcal contamination. The results showed that PCHSφ could provide a significantly higher removal of staphylococci, including resistant strains, compared with disinfectants (-76%, p < 0.05) and PCHS alone (-50%, p < 0.05). Extraordinary sporadic chlorine disinfection appeared compatible with PCHSφ, while frequent routine chlorine usage inactivated the probiotic/phage components, preventing PCHSφ action. The collected data highlight the potential of a biological sanitation for better control of the infectious risk in healthcare facilities, without worsening pollution and AMR concerns.

Pioneer colonizers: Bacteria that alter the chicken intestinal morphology and development of the microbiota.

Microbes commonly administered to chickens facilitate development of a beneficial microbiome that improves gut function, feed conversion and reduces pathogen colonization. Competitive exclusion products, derived from the cecal contents of hens and shown to reduce Salmonella colonization in chicks, possess important pioneer-colonizing bacteria needed for proper intestinal development and animal growth. We hypothesized that inoculation of these pioneer-colonizing bacteria to day of hatch chicks would enhance the development of their intestinal anatomy and microbiome. A competitive exclusion product was administered to broiler chickens, in their drinking water, at day of hatch, and its impact on intestinal morphometrics, intestinal microbiome, and production parameters, was assessed relative to a control, no treatment group. 16S rRNA gene, terminal restriction fragment length polymorphism (T-RFLP) was used to assess ileal community composition. The competitive exclusion product, administered on day of hatch, increased villus height, villus height/width ratio and goblet cell production ∼1.25-fold and expression of enterocyte sugar transporters 1.25 to 1.5-fold in chickens at 3days of age, compared to the control group. As a next step, chicks were inoculated with a defined formulation, containing Bacteroidia and Clostridia representing pioneer-colonizing bacteria of the two major bacterial phyla present in the competitive exclusion product. The defined formulation, containing both groups of bacteria, were shown, dependent on age, to improve villus height (jejunum: 1.14 to 1.46-fold; ileum: 1.17-fold), goblet cell numbers (ileum 1.32 to 2.51-fold), and feed efficiency (1.18-fold, day 1) while decreasing Lactobacillus ileal abundance by one-third to half in birds at 16 and 42days of age, respectively; compared to the phosphate buffered saline treatment group. Therefore, specific probiotic formulations containing pioneer colonizing species can provide benefits in intestinal development, feed efficiency and body weight gain.