Background Accumulating evidence has underscored the role of gut fungal microbiota (mycobiota) in the development of inflammatory bowel disease. We aimed to isolate a Malassezia strain directly from the human intestine mucosal surface from the patients with ulcerative colitis (UC) and investigated its genome and virulence in comparison with the same fungal species isolated from the human skin. Methods Mucosal lavage samples were collected separately from colonic areas with and without inflammation in patients with UC. Samples from healthy individuals (HT) were obtained in the same manner as from patients with UC at sigmoid or descending colon. Skin samples were taken from HT in our previous work. DNA was extracted from these lavage samples, and fungal isolation was conducted using PCR amplification with ITS4 and ITS5 primers. Comprehensive analysis and comparison of the genomes, transcriptomes, and virulence between M. globosa gut isolates and those of M. globosa strains isolated from the skin were performed. To determine the contribution of M. globosa gut isolates to exacerbating inflammation, 1107 fungal cells were orally gavaged to DSS-induced colitis mouse model for three days. Results Total 56 and 11 intestinal water-lavage samples from 29 UC patients and 11 HT were obtained respectively. The α- and b-diversities of mycobiota showed no significant differences between the groups, patients with UC vs. HT or the sites with inflammation vs. non-inflammation of the patient with UC. Malassezia was the fifth most frequently found fungal genus throughout the samples, and live fungal strains belong to 28 and 7 different species were isolated from the patients with UC and HT, respectively. The patients with UC tend to have higher frequency of M. globosa and M. restricta than HT in their gut mucosal surface with inflammation. Whole genome sequencing showed no specific genomic characteristics between gut-isolated M. globosa and skin-isolated M. globosa. However, gut-isolated M. globosa were suffered more from the higher oxygen levels than the skin isolates in different oxygen concentrations. In a mouse model, gut-isolated M. globosa exhibited a more pronounced exacerbation of DSS-induced colitis and elevated production of inflammatory cytokines, including TNF-a, IL-6, IL-12p40, IL-1b, and IL-18, while the skin isolates showed no difference compared to the negative control (Figure). Conclusion Our data shed new light on the pivotal role of M. globosa in the pathogenesis of UC, highlighting the potential influence of niche-specific adaptations on the virulence of this fungus. These findings provide critical insights into the complex interplay between the member of the gut mycobiota and host health.

中文翻译：

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P1229 马拉色菌在溃疡性结肠炎患者中的作用和特定适应

背景 越来越多的证据强调了肠道真菌微生物群（真菌群）在炎症性肠病发展中的作用。我们的目的是直接从溃疡性结肠炎（UC）患者的人肠粘膜表面分离马拉色菌菌株，并与从人类皮肤分离的相同真菌物种进行比较，研究其基因组和毒力。方法 分别采集 UC 患者有炎症和无炎症的结肠区域的粘膜灌洗样本。健康个体 (HT) 的样本采用与乙状结肠或降结肠 UC 患者相同的方式获取。皮肤样本取自我们之前工作中的 HT。从这些灌洗样品中提取 DNA，并使用 ITS4 和 ITS5 引物进行 PCR 扩增来进行真菌分离。对球形分枝杆菌肠道分离株与皮肤分离株的基因组、转录组和毒力进行了全面分析和比较。为了确定球形分枝杆菌肠道分离株对加剧炎症的作用，我们对 DSS 诱导的结肠炎小鼠模型口服 1107 个真菌细胞三天。结果共获得29例UC患者和11例HT患者的肠道水洗样本56份和11份。真菌群的α-和b-多样性在各组之间、UC患者与HT患者之间或者UC患者的炎症部位与非炎症部位之间没有显着差异。马拉色菌是整个样本中第五常见的真菌属，从 UC 和 HT 患者中分别分离出属于 28 个和 7 个不同物种的活真菌菌株。UC患者的肠道粘膜表面有炎症，球状支原体和限制性支原体的出现频率往往高于HT。全基因组测序显示，肠道分离的球形分枝杆菌和皮肤分离的球形分枝杆菌之间没有特定的基因组特征。然而，在不同氧气浓度下，肠道分离的球形分枝杆菌比皮肤分离的分枝杆菌更容易受到较高氧气水平的影响。在小鼠模型中，肠道分离的球形分枝杆菌表现出 DSS 诱导的结肠炎更明显的恶化，并且炎性细胞因子的产生增加，包括 TNF-a、IL-6、IL-12p40、IL-1b 和 IL-18。而皮肤分离株与阴性对照相比没有显示出差异（图）。结论 我们的数据为球分枝杆菌在 UC 发病机制中的关键作用提供了新的线索，强调了生态位特异性适应对该真菌毒力的潜在影响。这些发现为肠道菌群成员与宿主健康之间复杂的相互作用提供了重要的见解。