This presentation is based on article titled "The Tongue Biofilm Meta-transcriptome Identifies Metabolic Pathways Associated with the Presence or Absence of Halitosis" as an application of transcriptomics in biomarkers discovery for halitosis.

1. The Tongue Biofilm Meta-transcriptome
Identifies Metabolic Pathways Associated
with the Presence or Absence of Halitosis
Course: Integrative System Biology

2. Introduction
• Halitosis is a highly prevalent condition characterized by oral malodor.
Halitosis
(VSC)
intra-oral H2S (112 ppb), CH3SH (26 ppb)
extra-oral [CH3]2S (8 ppb)
transient
6/3/2023 5:51 PM ASAB-NUST 2

3. Observations
1. VSCs are mainly produced by oral microbiota degradation of certain amino
acids.
2. Tongue coating in halitosis patients is thicker than that in healthy individuals.
3. Periodontitis patients have 6 times more thicker tongue coating as compared to
healthy individuals.
4. Hydrogen sulfide has cytotoxic and pro-inflammatory properties under certain
conditions, thus contributing to inflammation and tissue damage.
5. When the tongue microbiota of halitosis patients is compared to that of
halitosis-free individuals, VSCs producers such as Prevotella, Fusobacterium
and Leptotrichia are detected in higher proportions.
6/3/2023 5:51 PM ASAB-NUST 3

4. Objectives
• The study aimed at:
1. sequencing the total RNA of the microbial communities associated
with tongue coating to provide the first metatranscriptomic profile of
tongue-associated biofilms under halitosis-free and halitosis
conditions.
2. relating microbial activity to specific metabolic pathways, thereby
shedding light to the underlying mechanisms of VSC production and
to potential therapeutic approaches.
6/3/2023 5:51 PM ASAB-NUST 4

5. 6/3/2023 5:51 PM ASAB-NUST 5

6. Methodology
6/3/2023 5:51 PM ASAB-NUST 6

7. Bioinformatics Analysis
Calculation
of
abundance
matrix
• R scripts
• DESeq2
Pathway
Analysis
• KEGG
Annotation
of mRNA
reads
• Human Oral
Microbiome
Database
(HOMD)
Identificatio
n of human
and
microbial
ribosomal
seq
• Human
Genome
• SILVA
Trimming
of reads
• PRINSEQ
Sequencing
• FISABIO
6/3/2023 5:51 PM ASAB-NUST 7

8. 1. Changes in Active Microbial Proportions
6/3/2023 5:51 PM ASAB-NUST 8

9. 6/3/2023 5:51 PM ASAB-NUST 9

10. 2. Microbial Differences in Gene Expression
Profiles
6/3/2023 5:51 PM ASAB-NUST 10

11. 6/3/2023 5:51 PM ASAB-NUST 11

12. 3. Differential Gene Expression Profiles
6/3/2023 5:51 PM ASAB-NUST 12

13. 6/3/2023 5:51 PM ASAB-NUST 13

14. Conclusion
• An elevated concentration of H2S (hydrogen sulfide), or its
combination with CH3SH (methyl mercaptan), are associated with
dysbiosis of the tongue microbiota.
• The changes in active microbiota composition is associated with an
increase in VSCs concentration.
• Genes involved in VSCs production identify several routes by which
the bacterial communities in halitosis-free individuals consume VSCs
to transform them in non-halitosis compounds.
• Relationship between halitosis and a repression of genes responsible
for nitrate reduction is identified.
6/3/2023 5:51 PM ASAB-NUST 14

15. Reference Paper
6/3/2023 5:51 PM ASAB-NUST 15