Potential antibacterial and anti-biofilm effects of Anoectochilus roxburghii rhizome cultures

Anoectochilus roxburghii (Wall.) Lindl. is a precious herb plant and its rhizome cultures can be used as an alternative plant material. To utilize rhizomes in practical production, this study investigated the antibacterial and anti-biofilm effects of the rhizome extract (RhE) from (A) roxburghii , and further clarified the antibacterial mechanism. Results showed that RhE inhibited the growth of all tested bacterial species ( Escherichia coli , Pseudomonas aeruginosa , Staphylococcus aureus , and Bacillus subtilis ) and the highest inhibitory zone (18.6 mm) was found on (B) subtilis , which was 4.8 mm more than the extract (PE) from the field-grown plants of (A) roxburghii . The RhE treatment increased the leakage of the alkaline phosphatase, electrolyte, nucleic acid, and protein of (B) subtilis , indicating that the cell permeability was increased. Furthermore, RhE inhibited the respiration of B. subtilis and decreased the activity eof the key enzyme (glucose-6-phosphate dehydrogenase) in the hexose monophosphate (HMP) pathway, proving that RhE was involved in the HMP pathway. In addition, RhE inhibited bacterial biofilm formation, which was higher than PE; Among the four tested bacteria, RhE treatment had strong inhibitory effect on biofilm formation of P. aeruginosa and B. subtilis . The findings suggested that A. roxburghii rhizome cultures are the potential material in the production of antibacterial and anti-biofilm products.