Methylotrophic bacteria from underarm of human: Isolation, molecular detection, antibiofilm activity, and toxicity property

Abstract

Background: Methylotrophic bacteria are a group of bacteria that capable in utilize one-carbon and reduced carbon compounds as a source of carbon and energy for their growth. This ability was supported by the presence of mxaF gene that encodes methanol dehydrogenase (MDH) enzyme. Previous studies have reported the presence of these bacteria in the mouth and feet of human. However, research about the presence of methylotrophic bacteria in human underarm is still limited. Biofilm is known as one of the self-defense mechanisms against the antibacterial agents, possessed by several bacteria, resulting in resistance and many chronic infections. This research is aimed to isolate methylotrophic bacteria from underarm of human, detect the genes encode MDH, screen the antibiofilm activity of these bacteria, and continue to determine their toxicity property. Methods and materials: Methylotrophic bacteria were isolated from 80 participants. Subsequently, molecular detection of mxaF gene as marker of these bacteria was conducted by performing polymerase chain reaction (PCR) using specific primer, namely f1003 and r1561. Then, antibiofilm activity assay was performed in two different mechanisms (inhibition and destruction activity) at two different concetration treatment (5 and 10% of crude extract). Finally, toxicity assay was performed by using brine shrimp lethality assay (BSLA) to determine LC50 values of these isolates. Results: In total, 120 isolates were isolated from 80 participants, and mxaF genes of 54 isolates were successfully amplified. Most of the methylotrophic bacteria exhibited specific antibiofilm activity against specific pathogen at specific concentration. The highest antibiofilm activity was demonstrated by isolate B2.4, which was identified as Serratia marcescens through 16S rRNA gene sequencing method. This isolate showed the highest inhibition activity against ETEC and also the destruction activity against Staphylococcus aureus ATCC 25923 with the result up to 65.09% and 58.56%, respectively. Then, five selected isolates showed LC50 values greater than 1000 μg/mL, indicating that these isolates had no cytotoxic effect. Conclusion: Further study needs to be conducted to explore other molecular detection of methylotrophic bacteria, other than using mxaF gene as a molecular marker. Moreover, it is also important to characterize, purify, and do more advanced toxicity assay on the potential bioactive compound.