Life history drives the assembly of the bacterial community associated with the Horn fly, Haematobia irritans L. (Diptera: Muscidae).

Parabronema skrjabini (Nematoda: Habronematidae) infection and development in the intermediate host-Haematobia irritans (Linnaeus, 1758) in Inner Mongolia, China

Parabronema skrjabini is one of the most harmful nematodes to camels and is responsible for economic losses in animal husbandry industry. There is an urgent need for in-depth studies of potential vectors of the nematode due to its scant regarding information. As previous studies indicated that flies may be the vectors of P. skrjabini, we captured flies in the main camel-producing areas of Inner Mongolia. After autopsy of the specimens of two species of horn flies, we observed the morphology of the suspected nematode larvae found in them. Internal transcribed spacer ribosomal-DNA gene sequences were considered the best candidate to confirm the species of the larvae found. Our results showed that the homology compared with P. skrjabini was 99.5% in GenBank. Subsequently, we preliminarily identified two species of horn flies through morphological observation and then sequenced the mitochondrial-DNA-gene cytochrome oxidase subunit I obtained from two species of horn flies, with 100 and 99.2% similarity to sequences deposited in GenBank, respectively. Thus, we identified Haematobia titillans and Haematobia irritans and provided evidence for their potential role as vectors of parabronemosis. Our study provides reference for future research on the life history of the nematode and the vectors of parabronemosis.

The extent to which the distribution of soil bacteria is controlled by local environment vs. spatial factors (e.g. dispersal, colonization limitation, evolutionary events) is poorly understood and widely debated. Our understanding of biogeographic controls in microbial communities is likely hampered by the enormous environmental variability encountered across spatial scales and the broad diversity of microbial life histories. Here, we constrained environmental factors (soil chemistry, climate, above-ground plant community) to investigate the specific influence of space, by fitting all other variables first, on bacterial communities in soils over distances from m to 10² km. We found strong evidence for a spatial component to bacterial community structure that varies with scale and organism life history (dispersal and survival ability). Geographic distance had no influence over community structure for organisms known to have survival stages, but the converse was true for organisms thought to be less hardy. Community function (substrate utilization) was also shown to be highly correlated with community structure, but not to abiotic factors, suggesting nonstochastic determinants of community structure are important Our results support the view that bacterial soil communities are constrained by both edaphic factors and geographic distance and further show that the relative importance of such constraints depends critically on the taxonomic resolution used to evaluate spatio-temporal patterns of microbial diversity, as well as life history of the groups being investigated, much as is the case for macro-organisms.

Bacteria and fungi are important mediators of biogeochemical processes and play essential roles in the establishment of plant communities, which makes knowledge about their recovery after extreme disturbances valuable for understanding ecosystem development. However, broad ecological differences between bacterial and fungal organisms, such as growth rates, stress tolerance, and substrate utilization, suggest they could follow distinct trajectories and show contrasting dynamics during recovery. In this study, we analyzed both the intra-annual variability and decade-scale recovery of bacterial and fungal communities in a chronosequence of reclaimed mined soils using next-generation sequencing to quantify their abundance, richness, β-diversity, taxonomic composition, and cooccurrence network properties. Bacterial communities shifted gradually, with overlapping β-diversity patterns across chronosequence ages, while shifts in fungal communities were more distinct among different ages. In addition, the magnitude of intra-annual variability in bacterial β-diversity was comparable to the changes across decades of chronosequence age, while fungal communities changed minimally across months. Finally, the complexity of bacterial cooccurrence networks increased with chronosequence age, while fungal networks did not show clear age-related trends. We hypothesize that these contrasting dynamics of bacteria and fungi in the chronosequence result from (i) higher growth rates for bacteria, leading to higher intra-annual variability; (ii) higher tolerance to environmental changes for fungi; and (iii) stronger influence of vegetation on fungal communities.IMPORTANCE Both bacteria and fungi play essential roles in ecosystem functions, and information about their recovery after extreme disturbances is important for understanding whole-ecosystem development. Given their many differences in phenotype, phylogeny, and life history, a comparison of different bacterial and fungal recovery patterns improves the understanding of how different components of the soil microbiota respond to ecosystem recovery. In this study, we highlight key differences between soil bacteria and fungi during the restoration of reclaimed mine soils in the form of long-term diversity patterns, intra-annual variability, and potential interaction networks. Cooccurrence networks revealed increasingly complex bacterial community interactions during recovery, in contrast to much simpler and more isolated fungal network patterns. This study compares bacterial and fungal cooccurrence networks and reveals cooccurrences persisting through successional ages.

A coral's capacity to alter its microbial symbionts may enhance its fitness in the face of climate change. Recent work predicts exposure to high environmental variability may increase coral resilience and adaptability to future climate conditions. However, how this heightened environmental variability impacts coral-associated microbial communities remains largely unexplored. Here, we examined the bacterial and algal symbionts associated with two coral species of the genus Siderastrea with distinct life history strategies from three reef sites on the Belize Mesoamerican Barrier Reef System with low or high environmental variability. Our results reveal bacterial community structure, as well as alpha- and beta-diversity patterns, vary by host species. Differences in bacterial communities between host species were partially explained by high abundance of Deltaproteobacteria and Rhodospirillales and high bacterial diversity in Siderastrea radians. Our findings also suggest Siderastrea spp. have dynamic core bacterial communities that likely drive differences observed in the entire bacterial community, which may play a critical role in rapid acclimatization to environmental change. Unlike the bacterial community, Symbiodiniaceae composition was only distinct between host species at high thermal variability sites, suggesting that different factors shape bacterial versus algal communities within the coral holobiont. Our findings shed light on how domain-specific shifts in dynamic microbiomes may allow for unique methods of enhanced host fitness.

Selection pressures due to parasitism play an important role in driving the evolution of life history traits of birds in general and of behaviour at the nest in particular. Eggshell bacterial load has been shown to predict hatching failure (i.e. the probability of embryo infection) but the relationships between the bacterial environment of the nest and life history characteristics of birds remain poorly investigated. We explored interspecific variation in eggshell bacterial load of mesophilic bacteria,Enterococcusspp.,Staphylococcusspp. andEnterobacteriaceaegroups across 24 bird species and assessed whether bacterial load is associated with breeding traits. Interspecific variation was much higher than intraspecific variation for all measures of bacterial load even after controlling for annual variation. Thus, we were able to assess the correlation between bacterial community characteristics and life history traits. After correcting for phylogenetic effects, we found that nest type, the use of feathers or plants as lining material, and incubation behaviour explained a significant proportion of the variance in bacterial communities on eggshells. The strength of these associations depended on study year, suggesting an important role of environmental conditions for eggshell bacterial load or community. Overall, these results suggest that bacteria on eggshells are associated with bird species traits, probably because birds are mediating the deleterious effect of eggshell microbes through behavioural traits that modify bacterial load.

Bacterial communities are fundamental symbionts of corals. However, the process by which bacterial communities are acquired across the life history of corals, particularly in larval and early juvenile stages, is still poorly characterized. Here, transfer of bacteria of the Scleractinian coral Acropora digitifera from adults to spawned egg-sperm bundles was analyzed, as well as acquisition across early developmental stages (larvae and newly settled spat), and 6-month-old juveniles. Larvae were reared under manipulated environmental conditions to determine the source (maternal, seawater, or sediment) of bacteria likely to establish symbiotic relationships with the host using amplicon sequencing of the 16S rRNA gene. Maternal colonies directly transferred bacteria from the families Rhodobacteraceae, Cryomorphaceae, and Endozoicimonaceae to egg-sperm bundles. Furthermore, significant differences in the microbial community structure were identified across generations, yet the structure of the coral bacterial community across early life history stages was not impacted by different environmental rearing conditions. These data indicate that the uptake and structure of bacterial communities is developmentally, rather than environmentally, regulated. Both maternal coral colonies and ubiquitous bacteria found across environmental substrates represent a potential source of symbionts important in establishing the coral microbiome. Uniquely, we report the presence of variation with ontogeny of both the core and resident bacterial communities, supporting the hypothesis that microbial communities are likely to play specific roles within the distinct life history stages of the coral host.

Bacterial symbionts are known to facilitate a wide range of physiological processes and ecological interactions for their hosts. In spite of this, caterpillars with highly diverse life histories appear to lack resident microbiota. Gut physiology, endogenous digestive enzymes, and limited social interactions may contribute to this pattern, but the consequences of shifts in social activity and diet on caterpillar microbiota are largely unknown. Phengaris alcon caterpillars undergo particularly dramatic social and dietary shifts when they parasitize Myrmica ant colonies, rapidly transitioning from solitary herbivory to ant tending (i.e., receiving protein‐rich regurgitations through trophallaxis). This unique life history provides a model for studying interactions between social living, diet, and caterpillar microbiota. Here, we characterized and compared bacterial communities within P. alcon caterpillars before and after their association with ants, using 16S rRNA amplicon sequencing and quantitative PCR. After being adopted by ants, bacterial communities within P. alcon caterpillars shifted substantially, with a significant increase in alpha diversity and greater consistency in bacterial community composition in terms of beta dissimilarity. We also characterized the bacterial communities within their host ants (Myrmica schencki), food plant (Gentiana cruciata), and soil from ant nest chambers. These data indicated that the aforementioned patterns were influenced by bacteria derived from caterpillars’ surrounding environments, rather than through transfers from ants. Thus, while bacterial communities are substantially reorganized over the life cycle of P. alcon caterpillars, it appears that they do not rely on transfers of bacteria from host ants to complete their development.

ABSTRACTFish bacterial communities provide functions critical for their host’s survival in contrasting environments. These communities are sensitive to environmental-specific factors (i.e., physicochemical parameters, bacterioplankton), and host-specific factors (i.e., host genetic background). The relative contribution of these factors shaping Amazonian fish bacterial communities is largely unknown. Here, we investigated this topic by analyzing the gill bacterial communities of 240 wild flag cichlids (Mesonauta festivus) from 4 different populations (genetic clusters) distributed across 12 sites in 2 contrasting water types (ion-poor/acidic black water and ion-rich/circumneutral white water). Transcriptionally active gill bacterial communities were characterized by a 16S rRNA metabarcoding approach carried on RNA extractions. They were analyzed using comprehensive data sets from the hosts genetic background (Genotyping-By-Sequencing), the bacterioplankton (16S rRNA) and a set of 34 environmental parameters. Results show that the taxonomic structure of 16S rRNA gene transcripts libraries were significantly different between the 4 genetic clusters and also between the 2 water types. However, results suggest that the contribution of the host’s genetic background was relatively weak in comparison to the environment-related factors in structuring the relative abundance of different active gill bacteria species. This finding was also confirmed by a mixed-effects modeling analysis, which indicated that the dissimilarity between the taxonomic structure of bacterioplanktonic communities possessed the best explicative power regarding the dissimilarity between gill bacterial communities’ structure, while pairwise fixation indexes (FST) from the hosts’ genetic data only had a weak explicative power. We discuss these results in terms of bacterial community assembly processes and flag cichlid fish ecology.IMPORTANCE Host-associated microbial communities respond to factors specific to the host physiology, genetic backgrounds, and life history. However, these communities also show different degrees of sensitivity to environment-dependent factors, such as abiotic physico-chemical parameters and ecological interactions. The relative importance of host- versus environment-associated factors in shaping teleost bacterial communities is still understudied and is paramount for their conservation and aquaculture. Here, we studied the relative importance of host- and environment-associated factors structuring teleost bacterial communities using gill samples from a wild Amazonian teleost model (Mesonauta festivus) sampled in contrasting habitats along a 1500 km section of the Amazonian basin, thus ensuring high genetic diversity. Results showed that the contribution of the host’s genetic background was weak compared to environment-related bacterioplanktonic communities in shaping gill bacterial assemblages, thereby suggesting that our understanding of teleost microbiome assembly could benefit from further studies focused on the ecological interplay between host-associated and free-living communities.

Bacteria are part of the insect gut system and influence many physiological traits of their host. Gut bacteria may even reduce or block the transmission of arboviruses in several species of arthropod vectors. Culicoides biting midges are important arboviral vectors of several livestock and wildlife diseases, yet limited information is available on their gut bacterial communities. Addressing this gap will help inform how these communities can be manipulated and ultimately used as novel tools to control pathogens. To assess how bacterial communities change during the life stages of lab-reared C. nubeculosus and C. sonorensis, endosymbiotic bacteria were identified using Illumina sequencing of 16S rRNA and taxonomically characterised. Analyses were conducted to determine how gut bacterial communities in adults are influenced by species identity and geographic distance among biting midge populations. Communities of the two lab-reared Culicoides species significantly changed after pupation and with maturation into 6-day-old adults. Pseudomonas, Burkholderiaceae and Leucobacter bacteria were part of a core community that was trans-stadially transmitted and found throughout their life cycle. Among field-collected biting midges, the bacterial communities were unique for almost each species. Cardinium, Rickettsia and Wolbachia were some of the most abundant bacteria in midges collected from wetlands. Only Pseudomonas was present in high relative abundance in all field-collected species. In this study, species identity, as well as geographic distance, influenced the gut bacterial communities and may partly explain known inter- and intra-species variability in vector competence. Additionally, stably associated bacterial species could be candidates for paratransgenic strategies to control vector-borne pathogens.

GUT BACTERIAL DIVERSITY BETWEEN POLYGRID LAND SNAILS REFLECT ENVIRONMENTAL DIFFERENCES

An improved method for rearing horn flies, Haematobia irritans irritans (L.), on bovine hosts is reported in which adult flies were confined in cages fastened to the backs of stanchioned cattle. Survival of females was 75% per day and longevity averaged 3.5 days. Oviposition began when females were 2 days old. The number of eggs produced per female entering the population averaged 20.1, and a single female could produce up to 112 eggs in her lifetime. Immature survival averaged 48.9%. The generation growth rate was 4.91 females per female. Generation time was 20 days at 25°C. Approximately 1–3.8 g of manure per egg is recommended for larval rearing. Pupae can be stored at 10°C for up to 18 days with little loss in viability. Methods for using the life history information for optimizing rearing are discussed.

The moose fly, Haematobosca alcis (Snow) is abundant in Yellowstone National Park wherever its host, Shiras' Moose, occurs. Descriptions of the 2nd and 3rd instars, the puparium, and both sexes are given. H. alcis is similar morphologically to its European congener, H. stimulans , but can be distinguished particularly by size, biology and host preference. Except for the difference in host specificity, the biology of H. alcis is similar to that of Haematobia irritans . The females oviposit in fresh moose droppings, depositing about 10 eggs each 0.5-3 min after a moose defecates. Development from egg to adult requires about 16 days at 21°C in the laboratory. Flies emerge from overwintered pupae in late spring (usually early June) and adults are active until late September. The haematophagous adults are host specific for moose and remain with the host animal, except when females are ovipositing. Occasional specimens were attracted to horses when near moose habitat and one male attempted to pierce the skin of man. Moose did not appear particularly annoyed by H. alcis , even when 500 or more flies were present/animal.

Understanding the ecological patterns of rhizosphere microbial communities is critical for propelling sustainable agriculture and managing ecosystem functions by exploiting microorganisms. However, this knowledge is still unclear, especially under host-associated large-scale and regarding the comparison between bacteria and fungi. We examined community assembly processes and community characters including environmental thresholds and co-occurrence patterns across the cultivatable area of Panax notoginseng for bacteria and fungi. Both are vital members of the rhizosphere but differ considerably in their life history and dispersal potentiality. Edaphic factors drove the parallel variations of bacterial and fungal communities. Although bacterial and fungal communities exhibited similar biogeographic patterns, the assembly of fungi was more driven by dispersal limitation than selection compared with bacteria. This finding supported the ‘size-dispersal’ hypothesis. pH and total nitrogen respectively mediated the relative importance of deterministic and stochastic processes in shaping bacterial and fungal communities. In addition, fungal communities exhibited potentially broader environmental thresholds and more modular co-occurrence patterns than bacteria (bacteria: 0.67; fungi: 0.78). These results emphasized the importance of dispersal limitation in structuring rhizosphere microbiota and shaping community features of ecologically distinct microorganisms. This study provides insights into the improved prediction and management of the key functions of rhizosphere microbiota.

Zooplankton provides bacteria with a complex microhabitat richen in organic and inorganic nutrients, and the bacteria community also changes the physiochemical conditions for zooplankton, where the symbiotic relationship between them plays an important role in the nutrient cycle. However, there are few studies on the effect of associated bacteria on the population dynamics of rotifers. In order to make clear their relationships, we reconstructed the associated bacterial community in Brachionus calyciflorus culture, and examined the life history and population growth parameters, and analyzed the diversity and community composition of the associated bacteria at different growth stages of B. calyciflorus. The results showed that the addition of bacteria from natural water can promote the population growth and asexual reproduction of B. calyciflorus, but has no significant effect on sexual reproduction, exhibited by the improvement of its life expectancy at hatching, net reproduction rates and intrinsic growth rate, no significant effects on the generation time and mixis ratio of offspring. It was found that the B. calyciflorus-associated bacterial community was mainly composed of Proteobacteria, Bacteroidota, Actinobacteriota, Cyanobacteria and Firmicutes. Through correlation network analysis, the members of Burkholderiales, Pseudomonadales, Micrococcales, Caulobacterales and Bifidobacteriales were the keystone taxa of B. calyciflorus-associated bacteria. In addition, the relative abundance of some specific bacteria strains increased as the population density of B. calyciflorus increased, such as Hydrogenophaga, Acidovorax, Flavobacterium, Rheinheimera, Novosphingobium and Limnobacter, and their relative abundance increased obviously during the slow and exponential phases of population growth. Meanwhile, the relative abundance of adverse taxa (such as Elizabethkingia and Rickettsiales) decreased significantly with the increase in rotifer population density. In conclusion, the closely associated bacteria are not sufficient for the best growth of B. calyciflorus, and external bacterioplankton is necessary. Furthermore, the function of keystone and rare taxa is necessary for further exploration. The investigation of the symbiotic relationship between zooplankton-associated bacterial and bacterioplankton communities will contribute to monitoring their roles in freshwater ecosystems, and regulate the population dynamics of the micro-food web.