Thuy Do ^1* Dongmei Deng ² Naile Dame-Teixeira ³

• ¹ Oral Biology, School of Dentistry, University of Leeds, Leeds, West Yorkshire, United Kingdom
• ² University of Amsterdam and VU University Amsterdam, 1081 LA Amsterdam, The Netherlands., Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, VU Amsterdam, Amsterdam, Netherlands
• ³ Departamento of Dentistry, Faculty of Health Sciences, University of Brasília, Brasília, Brazil

to explore the cutting-edge research on oral health and systemic diseases. 13Our first volume collated 17 insightful papers exploring the use of microbial meta-omics data to 14 better understand the complex biological context of health and disease. These contributions 15 provided a comprehensive overview of the current state of knowledge and future directions in the 16 field of oral microbiome research using NGS technologies. NGS technologies hold immense 17 potential for developing strategies to modulate the oral microbiome for improved overall health. A 18 key theme emerging from these studies is the significant impact of systemic conditions, such as 19 hypertension and hyperglycemia, and dysbiosis in distant body sites, like the gut, on the oral 20 microbiota via the oral-gut axis. This intricate connection between the oral cavity and the gut 21 warrants significant attention. In this volume, Lin et al investigated the presence of oral bacteria 22 in the gut of patients without any history of intestinal disorders. Their research give compelling 23 evidence for the transmission of oral taxa, commonly residing on the tongue dorsum, to the 24 rectum. Notably, they discovered that the translocation of oral bacteria to the rectum was 25 significantly more prevalent in participants with advanced age, hypertension, and those utilizing 26 proton pump inhibitors. 27This volume also features an interesting perspective by Filardo et al that explores the human 28 microbiome as a "hidden organ", with important contribution to host functions and significant 29 influence on human health. The review provides insights into human microbiome profiling, 30 describing various metagenomic methods, including 16S rRNA gene sequencing and its 31 associated biases (partial or full-length of the 16S rRNA gene) for the accurate identification of 32 bacteria to the species level, as well as biases associated with different sequencing platforms, 33 that may lead to the underestimation of the biodiversity of the microbiota being studied. 34For a more comprehensive picture, shotgun metagenomics offers a deeper taxonomic and 35 functional characterisation of the microbiome (de Cena et al., 2021, Kifle et al., 2024). While first 36 and second-generation sequencing technologies revolutionised the field by enabling higher-resolution analyses, further advancements have brought about third-generation platforms like 38 PacBio and Oxford Nanopore Technologies. These platforms offer long-read sequencing, which, 39 when combined with short-read methods (although admittedly more expensive), can significantly 40 improve coverage and assembly performance, facilitating the detection of low-abundance 41 species. This combined approach would provide a more thorough characterisation of the 42 microbiota and offer a clearer picture of microbial interactions during the transition to dysbiosis 43 (de Cena et al., 2021). However, the high cost of combining these sequencing approaches 44 remains a significant obstacle. This cost disparity leads to a major limitation in the current data which facilitates collaboration, enables new discoveries, and saves time and resources. However, 76 challenges such as incomplete metadata, incompatible software, and lack of standardisation 77 hinder data reuse. Implementing "FAIR" principles can address these issues by ensuring data is 78 "findable, accessible, interoperable, and reusable". This can lead to more efficient data handling, 79 faster insights, and reduced research costs, through the deployment of a user-friendly framework 80 that promotes inter-disciplinary collaboration. Furthermore, we argue that future studies require 81 much more detailed metadata. Research on the oral microbiome and systemic health should 82 include comprehensive data on the donor's oral health, including periodontal disease and caries, 83 as well as well-characterised and reproducible disease diagnoses. However, there are some 84 concerns regarding General Data Protection Regulation (GDPR) for data privacy with regards to 85 patients' data information, which may limit such implementation in healthcare research. 86In conclusion, the oral microbiome undeniably impacts overall human health. A deeper 87 understanding of host-microbe interactions can inform targeted strategies for disease prevention 88 and treatment. This knowledge can guide the development of novel preventive strategies through 89 microbiome modulation. Moreover, achieving predictive health and disease models for 90 personalised therapies focused on restoring a healthy microbiome will necessitate collaboration 91 between microbiologists and clinicians to strengthen the connection between biological and 92 clinical characteristics. 93 94 95