Metabolic diversity in commensal protists regulates intestinal immunity and trans-kingdom competition

The microbiota influences intestinal health and physiology, yet the contributions of commensal protists to the gut environment have been largely overlooked. Here, we discover human- and rodent-associated parabasalid protists, revealing substantial diversity and prevalence in nonindustrialized human populations. Genomic and metabolomic analyses of murine parabasalids from the genus Tritrichomonas revealed species-level differences in excretion of the metabolite succinate, which results in distinct small intestinal immune responses. Metabolic differences between Tritrichomonas species also determine their ecological niche within the microbiota. By manipulating dietary fibers and developing in vitro protist culture, we show that different Tritrichomonas species prefer dietary polysaccharides or mucus glycans. These polysaccharide preferences drive trans-kingdom competition with specific commensal bacteria, which affects intestinal immunity in a diet-dependent manner. Our findings reveal unappreciated diversity in commensal parabasalids, elucidate differences in commensal protist metabolism, and suggest how dietary interventions could regulate their impact on gut health.

Hybrid assemblies of microbiome Blastocystis protists reveal evolutionary diversification reflecting host ecology

The most prevalent microbial eukaryote in the human gut is Blastocystis , an obligate commensal protist also common in many other vertebrates. Blastocystis is descended from free-living stramenopile ancestors; how it has adapted to thrive within humans and a wide range of hosts is unclear. Here, we cultivated six Blastocystis strains spanning the diversity of the genus and generated highly contiguous, annotated genomes with long-read DNA-seq, Hi-C, and RNA-seq. Comparative genomics between these strains and two closely related stramenopiles with different lifestyles, the lizard gut symbiont Proteromonas lacertae and the free-living marine flagellate Cafeteria burkhardae , reveal the evolutionary history of the Blastocystis genus. We find substantial gene content variability between Blastocystis strains. Blastocystis isolated from an herbivorous tortoise has many plant carbohydrate metabolizing enzymes, some horizontally acquired from bacteria, likely reflecting fermentation within the host gut. In contrast, human- isolated Blastocystis have gained many heat shock proteins, and we find numerous subtype- specific expansions of host-interfacing genes, including cell adhesion and cell surface glycan genes. In addition, we observe that human-isolated Blastocystis have substantial changes in gene structure, including shortened introns and intergenic regions, as well as genes lacking canonical termination codons. Finally, our data indicate that the common ancestor of Blastocystis lost nearly all ancestral genes for heterokont flagella morphology, including cilia proteins, microtubule motor proteins, and ion channel proteins. Together, these findings underscore the huge functional variability within the Blastocystis genus and provide candidate genes for the adaptations these lineages have undergone to thrive in the gut microbiomes of diverse vertebrates.

Commensal protists in reptiles display flexible host range and adaptation to ectothermic hosts

IMPORTANCE

Environmental factors like climate change and captive breeding can impact the gut microbiota and host health. Therefore, conservation efforts for threatened species may benefit from understanding how these factors influence animal microbiomes. Parabasalid protists are members of the mammalian microbiota that can modulate the immune system and impact susceptibility to infections. However, little is known about parabasalids in reptiles. Here, we profile reptile-associated parabasalids in wild and captive reptiles and find that captivity has minimal impact on parabasalid prevalence or diversity. However, because reptiles are cold-blooded (ectothermic), their microbiotas experience wider temperature fluctuation than microbes in warm-blooded animals. To investigate whether extreme weather patterns affect parabasalid-host interactions, we analyzed the gene expression in reptile-associated parabasalids and found that temperature differences significantly alter genes associated with host health. These results expand our understanding of parabasalids in this vulnerable vertebrate group and highlight important factors to be taken into consideration for conservation efforts.

Commensal protists in reptiles display flexible host range and adaptation to ectothermic hosts

Parabasalid protists recently emerged as keystone members of the mammalian microbiota with important effects on their host's health. However, the prevalence and diversity of parabasalids in wild reptiles and the consequences of captivity and other environmental factors on these symbiotic protists are unknown. Reptiles are ectothermic, and their microbiomes are subject to temperature fluctuations, such as those driven by climate change. Thus, conservation efforts for threatened reptile species may benefit from understanding how shifts in temperature and captive breeding influence the microbiota, including parabasalids, to impact host fitness and disease susceptibility. Here, we surveyed intestinal parabasalids in a cohort of wild reptiles across three continents and compared these to captive animals. Reptiles harbor surprisingly few species of parabasalids compared to mammals, but these protists exhibited a flexible host-range, suggesting specific adaptations to reptilian social structures and microbiota transmission. Furthermore, reptile-associated parabasalids are adapted to wide temperature ranges, although colder temperatures significantly altered the protist transcriptomes, with increased expression of genes associated with detrimental interactions with the host. Our findings establish that parabasalids are widely distributed in the microbiota of wild and captive reptiles and highlight how these protists respond to temperature swings encountered in their ectothermic hosts.

Transcriptional profiling identifies novel regulators of macrophage polarization

Macrophages are key inflammatory immune cells that display dynamic phenotypes and functions in response to their local microenvironment. Major advances have occurred in understanding the transcriptional, epigenetic, and functional differences in various macrophage subsets by in vitro modeling and gene expression and epigenetic profiling for biomarker discovery. However, there is still no standardized protocol for macrophage polarization largely due to the lack of thorough validation of macrophage phenotypes following polarization. In addition, transcriptional regulation is recognized as a major mechanism governing differential macrophage polarization programs and as such, many genes have been identified to be associated with each macrophage subset. However, the functional role of many of these genes in macrophage polarization is still unknown. Moreover, the role of other regulatory mechanisms, such as DNA methylation, in macrophage polarization remains poorly understood. Here, we employed an optimized model of human M1 and M2 macrophage polarization which we used for large-scale transcriptional and DNA methylation profiling. We were unable to demonstrate a role for DNA methylation in macrophage polarization, as no significant changes were identified. However, we observed significant changes in the transcriptomes of M1 and M2 macrophages. Additionally, we identified numerous novel differentially regulated genes involved in macrophage polarization, including CYBB and DHCR7 which we show as important regulators of M1 and M2 macrophage polarization, respectively. Taken together, our improved in vitro human M1 and M2 macrophage model provides new understandings of the regulation of macrophage polarization and candidate macrophage biomarkers.

Complications associated with intrathecal morphine in spine surgery: a retrospective study

Background

Supplemental intrathecal morphine (ITM) represents an option to manage postoperative pain after spine surgery due to ease of administration and ability to confer effective short-term analgesia at low dosages. However, whether ITM increases risk of surgical site infections (SSI), cerebrospinal fluid (CSF) leak, and incidental dural tears (IDT) has not been investigated. Therefore, this study was performed to determine the rates of SSI, CSF leak, and IDT in patients that received ITM.

Methods

Patients that underwent posterior instrumented fusion from January 2010 to 2016 that received ITM were compared to controls with respect to demographic, medical, surgical, and outcome data. Fisher's exact test was used to compare rates of SSI, CSF leak, and IDT between groups. Poisson regression was used to analyze complication rates after adjusting for the influence of covariates and potential confounders.

Results

A total of 512 records were analyzed. ITM was administered to 78 patients prior to wound closure. The remaining 434 patients compromised the control group. IDT was significantly more common among patients receiving ITM (P=0.009). Differences in rates of CSF leak and SSI were not statistically significant (P=0.373 and P=0.564, respectively). After compensating for additional variables, Poisson regression revealed a significant increase in rates of IDT (P=0.007) according to ITM injection and advanced age (P=0.014). There was no significant difference in rates of CSF leak or SSI after accounting for the additional variables (P>0.05).

Conclusions

ITM for pain control in posterior instrumented spinal fusion surgery was linked to increased likelihood of IDT but not CSF leaks or SSI. Age was also noted to be a significant predictor of IDT. Spine surgeons should weigh potential risks against benefits when deciding whether to administer ITM for postoperative pain management following spine surgery.