# _Lactobacillus rhamns GG_ as Biosensor for Oral and Systemic Health Conditions: A Pilot Study
## 3 Results and Discussion
Proteins with a black dot have significantly different expression, while proteins marked with a grey dot are not significant. (**a**) The volcano plot comparing control (BUF) and subject (SANT) groups. (**b**) The volcano plot comparing control (BUF) and subject (SLPA) groups. (**c**) The volcano plot comparing control (BUF) and subject (SLFU) groups. (**d**) The volcano plot comparing control (BUF) and subject (SLAN) groups. (**e**) The volcano plot comparing control (BUF) and (LAC) groups. (**f**) The volcano plot comparing control (BUF) and (SU10) groups. In Figure 2, key proteins, such as LRHM_0760, LRHM_1642 (Tagatose-6-phosphate kinase), and LRHM_2802 (Mannitol-specific phosphotransferase enzyme IIA component) were significantly downregulated in SLPA, with high statistical significance. Conversely, proteins such as LRHM_1938 (protein in stress response) and LRHM_1714 (Hydrolase) were upregulated (Figure 2b). Additionally, proteins such as CSTP1 and CTSG were downregulated, while KRT1 showed notable upregulation in the control group, with strong \(p\)-values, reflecting their potential biological significance. Overall, the volcano plot identified key proteins differentially expressed between BUF and SLPA, offering insights into their possible roles in the underlying biological processes. Protein LRHM_760 may be involved in nutrient acquisition or metabolic processes. The downregulation of this protein may occur due to direct inhibition by salivary components or a tactical bacterial response to conserve energy and resources under stressful conditions [25]. LRHM_1642 (cell division protein) might be associated with cell wall synthesis or maintenance [26]. The acidic pH and enzymatic activity of human saliva can alter the bacterial cell environment, leading to the downregulation of less critical proteins for immediate survival. This could involve the repression of genes through regulatory proteins that respond to environmental changes [25]. In Figure 2c, notably, the SLFU comparison led to a high number of proteins being displayed in the volcano plot, both upregulated and downregulated. For example, LRHM_2802, LRHM_2254, LRHM_0760, and LRHM_2528 were in regions indicating strong downregulation in SLFU, suggesting that these proteins may play a critical role in SLFU-specific pathways or responses. Conversely, proteins such as LRHM_2282, LRHM_0475, and LRHM_2219 exhibit upregulation in BUF, indicating increased activity under SLFU conditions. These findings highlight the dynamic modification of LRHM proteins in both situations, providing valuable targets for further investigation into their functional significance. Proteins such as LRHM_2802 (Mannitol-specific phosphotransferase enzyme IIA component) were downregulated. This protein participates in signaling or cellular transport. Salivary components may interfere with the signaling pathways that regulate the expression of this protein. For instance, the interaction between salivary mucins and bacterial surface proteins could result in the inhibition of specific genes, leading to a reduction in the synthesis of protein LRHM_2254, an acetyltransferase. Bacterial chemotaxis, metabolism, DNA replication, and other cellular processes are influenced by protein acetylation [27]. The presence of specific proteins and antimicrobial peptides in human saliva can interfere with metabolic processes, resulting in the downregulation of proteins involved in these processes [28]. In Figure 2d, notably, the significantly downregulated protein in SLPO is LRHM_1642 (cell division protein FtsI). This protein is involved in cell division, and saliva contains various enzymes and antimicrobial peptides that can disrupt bacterial cell division, leading to the downregulation of proteins involved in cell multiplication [29]. Proteins such as LRHM_2617, LRHM_2811, and LRHM_1714 were upregulated, indicating reduced functional activity under SLPO conditions compared to BUF. LRHM_2617 (Hydrolase) is the protein that plays a role in DNA replication and repair.