Diversity and functional analysis of salivary microflora of Indian Antarctic expeditionaries

Abstract

Introduction: The human oral microbiota continues to change phenotype by many factors (environment, diet, genetics, stress, etc.), throughout life with a major impact on human physiology, psychology, metabolism and immune system. Amongst one such factor with unique and extreme environmental conditions is Antarctica. The sea voyage to Antarctica has many risks than at station for expedition members. In this study, we investigated the influence of Antarctic sea voyage and stay at the Indian Antarctic station Maitri, on the health of Indian expedition members by using a metagenomic approach to explore oral biodiversity. Methods: Saliva samples were collected from 12 expedition members, at 3 different time points viz. before the start of the ship voyage, after the completion of the voyage and at the end of the stay at Antarctica. Samples were analyzed for whole genome and 16S rRNA sequencing. Result: The oral microbial diversity of the expedition members was significantly changed, during the days of sailing and after the stay at Antarctica. The oral microbiota comprised mainly of the phyla Firmicutes (46%, 29% & 36%); Proteobacteria (40%, 48%, & 44%), Bacteroidetes (10%, 22%, &14%), Fusobacterium and Actinobacteria (5%-1%) and Unclassified (17%, 25% & 23%), at three time points, respectively. Further, the differential analysis of microbes across all the phyla revealed 89, 157 and 157 OTUs genera. The altered microbiota indicated changes in amino acid, lipid and carbohydrate metabolism. Conclusion: Study suggests that understanding the compositional and functional differences in the oral microbiota of Antarctic expedition members, can lay the foundation to relate these differences to their health status. It will further demonstrate the need for providing improved management during ship voyage and stay in Antarctica.

Keywords: Antarctica; metabolism; metagenome; oral microbiota; saliva; stress.

Figure 1.

(a) represents the number of texas, Neon Green represents (T1), blue (T2), red (T3), share texas green (T1-T2), purple (T2-T3) brown (T1-T3) and gray (T1-T2-T3). (b) shows the fold changes in phyla at T1, T2 and T3 time points, dark blue represent maximum ‘Z’ score and white minimum.

Figure 2.

(a and d) show oral microbial abundance at phyla and genus level at three time points; (b and e) depict alpha diversities as antilog of Shannon index and (c and f) indicate beta diversity. All the data have p < 0.05.

Figure 3.

KEGG orthologs (KOs) in saliva microbiota in all individuals at different time points. The heat map shows the relative abundance of significant (p value <0.01) individual KEGG orthologs (Kos) calculated for time points T1, T2 and T3 samples using PICRUSt. Samples were clustered using the Euclidean distance measure.

Figure 4.

Principal coordinate analysis (PCoA) using STAMP v2.1.3 of predicted functional metagenomes between Time points T1, T2 and T3.

Figure 5.

Metagenomic functional predictions pair-wise comparison between the time points (T1 – T2), (T1 – T3) and (T2 – T3) for mean relative gene pathway abundance of significantly differentially abundant modules (ANOVA; p < 0.01).

Figure 6.

Representation of the CDS contigs annotation against (a) GO terms identified across T1, T2 & T3; (b) NR-protein; (c) GO blast and (d) Pfam abundance at various time points.