虽然肠道菌群在多种疾病如肠易激综合征、结肠癌和衰老中的影响已经被证明，但对其在改变其他感染性微生物属性方面的作用的研究仍然很少。在本研究中，我们研究了Blastocystis sp.和人类肠道菌群的关联和相互作用。我们研究了有和无Blastocystis sp. ST3感染的有症状和无症状个体的肠道菌群。我们测试了Blastocystis sp. ST3的表型和致病特征是否受其伴随菌群的变化影响。Blastocystis sp. ST3感染会改变细菌组成。其在无症状个体中的存在显示出显著的对微生物丰富度的影响，与有症状者相比。推断的宏基因组发现表明Blastocystis sp. ST3的寄生会导致微生物功能的改变。我们首次证明了细菌对Blastocystis sp.致病性的影响。当从有症状个体中分离出的Blastocystis sp.和来自无症状个体的Blastocystis sp.菌悬液共培养时，寄生虫表现出了增加的生长和减少的潜在致病表现。本研究也揭示了Blastocystis sp.感染可以影响微生物功能而对菌群多样性本身影响不大的证据。我们的结果还证明了肠道菌群在改变寄生虫特征方面的影响力，这成为不同研究中看到的寄生虫致病性矛盾结果的基础。我们的研究提供了证据表明，人类肠道中的无症状Blastocystis sp.可以在受肠道菌群的影响下被激活展现出病原特征。版权所有：©2023 Rajamanikam等人。本文是一篇采用创作共用许可协议发布的开放获取文章，允许在任何媒体中自由使用、分发和重制，只要原作者和来源被给予著作权归属。

Whilst the influence of intestinal microbiota has been shown in many diseases such as irritable bowel syndrome, colorectal cancer, and aging, investigations are still scarce on its role in altering the nature of other infective organisms. Here we studied the association and interaction of Blastocystis sp. and human intestinal microbiota. In this study, we investigated the gut microbiome of Blastocystis sp.-free and Blastocystis sp. ST3-infected individuals who are symptomatic and asymptomatic. We tested if the expression of phenotype and pathogenic characteristics of Blastocystis sp. ST3 was influenced by the alteration of its accompanying microbiota. Blastocystis sp. ST3 infection alters bacterial composition. Its presence in asymptomatic individuals showed a significant effect on microbial richness compared to symptomatic ones. Inferred metagenomic findings suggest that colonization of Blastocystis sp. ST3 could contribute to the alteration of microbial functions. For the first time, we demonstrate the influence of bacteria on Blastocystis sp. pathogenicity. When Blastocystis sp. isolated from a symptomatic individual was co-cultured with bacterial suspension of Blastocystis sp. from an asymptomatic individual, the parasite demonstrated increased growth and reduced potential pathogenic expressions. This study also reveals that Blastocystis sp. infection could influence microbial functions without much effect on the microbiota diversity itself. Our results also demonstrate evidence on the influential role of gut microbiota in altering the characteristics of the parasite, which becomes the basis for the contradictory findings on the parasite's pathogenic role seen across different studies. Our study provides evidence that asymptomatic Blastocystis sp. in a human gut can be triggered to show pathogenic characteristics when influenced by the intestinal microbiota.Copyright: © 2023 Rajamanikam et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.