Elevational Changes in Bacterial Microbiota Structure and Diversity in an Arthropod-Disease Vector

Testing for Consistency in Co-occurrence Patterns Among Bacterial Taxa Across the Microbiomes of Four Different Trematode Parasites

Elucidating the specific processes and drivers of community assembly in the host microbiome is essential to fully understand host biology. Toward this goal, an important first step is to describe co-occurrence patterns among different microbial taxa, which can be driven by numerous factors, such as host identity. While host identity can be an important influential factor on co-occurrence patterns, a limited number of studies have explored the relative importance of host identity after controlling for other environmental factors. Here, we examined microbial co-occurrence patterns in four phylogenetically distinct trematode species living within the same snail species, collected concomitantly from the same habitat. Our previous study determined that all these trematodes shared some bacterial taxa, and the relative abundance of microbial taxa differed among trematodes, possibly due to differences in their eco-physiological traits. Here, we specifically predict that pairwise microbial co-occurrence patterns also vary among trematode host species. Our results showed that co-occurrence patterns among eight microbial families varied greatly among the four trematode hosts, with some microbial families co-occurring in some trematode species, whereas no such patterns were observed in other trematodes. Our study suggests that the habitat identity (trematode species) and its associated biotic characteristics, such as physiological and ecological traits, can determine co-occurrence patterns among microbial taxa, with substantial effects on local community composition.

Contrasting alpha, beta, and gamma diversity in the littoral zones of mountain lakes: effects of habitat size and within-lake community structuring on bacterial biogeography

Research on microbial biogeography has revealed key patterns like the diversity-area relationship and distance-decay of similarity. However, how habitat size affects bacterial diversity in freshwater environments remains largely unclear. Here, we characterize bacterial communities in the littoral zones of 10 mountain lakes in the Sierra Nevada, CA, ranging in surface area from 0.92 to 71.72 ha. Despite significant habitat size effects on community composition, dominant bacterial phyla were shared across lakes. We found no evidence for diversity-area relationships, either in single samples (alpha diversity) or cumulative lake-level samples (within-lake gamma diversity), when accounting for environmental variation. Moreover, within-lake beta diversity showed little spatial structuring, with similar bacterial community composition across samples regardless of geographic distance. Gamma diversity did not reach saturation with our sample size, and lake size had no effect on the predicted sample size necessary to reach gamma diversity saturation. Our findings offer new insights into diversity-area dynamics and spatial structuring by investigating alpha, beta, and gamma diversity in freshwater environments. Notably, individual water samples captured much of the bacterial community, with strong correlations between alpha and gamma diversity. These results advance our understanding of microbial biogeography and inform sampling designs for characterizing bacterial diversity in freshwater ecosystems.

Microbial community variations in adult Hyalomma dromedarii ticks from single locations in Saudi Arabia and Tunisia

Introduction

The camel-infesting tick, Hyalomma dromedarii, is a prominent ectoparasite in the Middle East and North Africa (MENA) region, critically impacting camel health and acting as a vector for tick-borne pathogens. Despite prior studies on its microbiota, the effects of geographic origin and sex on microbial community structure and functional stability remain poorly understood.

Methods

To address this, we characterized the bacterial microbiota of H. dromedarii ticks collected from camels in Tunisia (TUN) and Saudi Arabia (SA) using 16S rRNA gene sequencing, microbial network analysis, and metabolic pathway prediction.

Results

Our findings indicate a dominant presence of Francisella endosymbionts in Tunisian ticks, suggesting adaptive roles of H. dromedarii ticks in arid ecosystems. Keystone taxa, particularly Staphylococcus and Corynebacterium, were identified as central to microbial network structure and resilience. Moreover, network robustness analyses demonstrated enhanced ecological stability in the Tunisian tick microbiota under perturbation, indicative of higher resilience to environmental fluctuations compared to Saudi Arabian ticks. Additionally, functional pathway predictions further revealed geographically distinct metabolic profiles between both groups (Tunisia vs. Saudi Arabia and males vs. females), underscoring environmental and biological influences on H. dromedarii microbiota assembly.

Discussion

These results highlight region-specific and sex-specific microbial adaptations in H. dromedarii, with potential implications for pathogen transmission dynamics and vector resilience. Understanding these microbial interactions may contribute to improved strategies for tick control and tick-borne disease prevention.

Effect of Morchella esculenta polysaccharides on the rectal microbiota of mice challenged with lipopolysaccharides

Introduction

Intestinal dysfunction poses a severe problem by preventing the digestion and absorption of nutrients. The gut, being the most vital organ for these processes, plays a crucial role in ensuring our body receives the nutrients it needs. We explored the mitigating effect of Morchella esculenta polysaccharides (MEP) on intestinal injury induced by lipopolysaccharides (LPS) through the modulation of intestinal flora.

Methods

For this purpose, Kunming mice (KM) were divided into three groups, namely, PC, PM, and PY. Group PY was treated with MEP, while groups PM and PY were induced with LPS.

Results

The results showed that weight loss in the PM group was significantly greater than that in the PY group (P < 0.05), and the organ indexes of the lung and spleen in the PM group were significantly higher than those in the PC (P < 0.01) and PY (P < 0.05) groups. LPS caused severe injuries in KM mice in the PM group, characterized by broken villi. However, MEP treatment could alleviate this damage in the PY group, resulting in relatively intact villi. The serum analysis showed that tumor necrosis factor alpha (TNF-ɑ) (P < 0.01), interleukin 6 (IL-6) (P < 0.01), and 3,4-methylenedioxyamphetamine (MDA) (P < 0.05) levels were significantly higher in the PM group, while IL-10 (P < 0.001), superoxide dismutase (SOD) (P < 0.01) and glutathione peroxidase (GSH-Px) (P < 0.01) were significantly lower in that group. Interestingly, supplementation with MEP could lower the levels of TNF-ɑ, IL-10, IL-6, MDA while increasing the levels of superoxide dismutase (SOD) (P < 0.01) and GSH-Px. The gut microbiota analysis yielded 630,323 raw reads and 554,062 clean reads, identifying 3,390 amplicon sequencing variants (ASVs). One phylum and five genera were notably different among animal groups, including Escherichia_Shigella, Limosilactobacillus, unclassified_Geminicoccaceae, unclassified_Rhodobacteraceae, and Parabacteroides (P. distasonis).

Discussion

In conclusion, we found that MEP could mitigate the intestinal damage caused by LPS by modulating the inflammatory response, oxidative resistance, and intestinal flora of KM mice. Our results may provide insights into novel treatment options for intestine-related diseases.

The microbiota of Amblyomma americanum reflects known westward expansion

Amblyomma americanum, a known vector of multiple tick-borne pathogens, has expanded its geographic distribution across the United States in the past decades. Tick microbiomes may play a role shaping their host's life history and vectorial capacity. Bacterial communities associated with A. americanum may reflect, or enable, geographic expansion and studying the microbiota will improve understanding of tick-borne disease ecology. We examined the microbiota structure of 189 adult ticks collected in four regions encompassing their historical and current geographic distribution. Both geographic region of origin and sex were significant predictors of alpha diversity. As in other tick models, within-sample diversity was low and uneven given the presence of dominant endosymbionts. Beta diversity analyses revealed that bacterial profiles of ticks of both sexes collected in the West were significantly different from those of the Historic range. Biomarkers were identified for all regions except the historical range. In addition, Bray-Curtis dissimilarities overall increased with distance between sites. Relative quantification of ecological processes showed that, for females and males, respectively, drift and dispersal limitation were the primary drivers of community assembly. Collectively, our findings highlight how microbiota structural variance discriminates the western-expanded populations of A. americanum ticks from the Historical range. Spatial autocorrelation, and particularly the detection of non-selective ecological processes, are indicative of geographic isolation. We also found that prevalence of Ehrlichia chaffeensis, E. ewingii, and Anaplasma phagocytophilum ranged from 3.40-5.11% and did not significantly differ by region. Rickettsia rickettsii was absent from our samples. Our conclusions demonstrate the value of synergistic analysis of biogeographic and microbial ecology data in investigating range expansion in A. americanum and potentially other tick vectors as well.

Can Tick Microbiome Explain Nonlinear Relationship between Tick Abundance and Lyme Disease Incidence?

Ticks (Acari: Ixodida) are hematophagous ectoparasitic arachnids that feed on the blood of vertebrate hosts, posing significant concern due to their unrivaled capacity to transmit various pathogens, which surpasses those of all other known arthropod vectors [...].

Comparative Microbiome Analysis of Three Epidemiologically Important Tick Species in Latvia

(1) Background: Amplicon-based 16S rRNA profiling is widely used to study whole communities of prokaryotes in many niches. Here, we comparatively examined the microbial composition of three tick species, Ixodes ricinus, Ixodes persulcatus and Dermacentor reticulatus, which were field-collected in Latvia. (2) Methods: Tick DNA samples were used for microbiome analysis targeting bacterial 16S rDNA using next-generation sequencing (NGS). (3) Results: The results showed significant differences in microbial species diversity and composition by tick species and life stage. A close similarity between microbiomes of I. ricinus and I. persulcatus ticks was observed, while the D. reticulatus microbiome composition appeared to be more distinct. Significant differences in alpha and beta microbial diversity were observed between Ixodes tick life stages and sexes, with lower taxa richness indexes obtained for female ticks. The Francisella genus was closely associated with D. reticulatus ticks, while endosymbionts Candidatus Midichlorii and Candidatus Lariskella were associated with I. ricinus and I. persulcatus females, respectively. In I. ricinus females, the endosymbiont load negatively correlated with the presence of the Rickettsia genus. (4) Conclusions: The results of this study revealed important associations between ticks and their microbial community and highlighted the microbiome features of three tick species in Latvia.

Decontamination protocols affect the internal microbiota of ticks

Studies on the microbiota of ticks have promoted hypotheses about the combined effects of the bacterial community, its functional contributions to the tick's physiology or probable competition effects with some tick-borne pathogens. However, knowledge on the origin of the microbiota of newly hatched larvae is missing. This study aimed to elucidate the source(s) of the microbiota in unfed tick larvae, addressing the composition of the "core microbiota" and the best ways to decontaminate eggs for microbiota studies. We applied laboratory degree bleach washes and/or ultraviolet light treatments on engorged Rhipicephalus australis females and/or their eggs. No significant effects of these treatments on the reproductive parameters of females and the hatching rates of eggs were observed. However, the different treatments did show striking effects on the composition of the microbiota. The results indicated that bleach washes disrupted the internal tick microbiota in females, implying that bleach may have entered the tick and subsequently affected the microbiota. Furthermore, the analyses of results demonstrated that the ovary is a main source of tick microbiota, while the contribution of Gené's organ (a part of the female reproductive system that secretes a protective wax coat onto tick eggs) or the male's spermatophore requires further investigation. Further studies are needed to identify best practice protocols for the decontamination of ticks for microbiota studies.