The Effectiveness of <i>Limnobium laevigatum</i> in Inhibiting the Growth of Microbes Found in Lake Water

Limnobium laevigatum, commonly called Amazon frogbit, belongs to the Hydrocharitaceae family and thrives in freshwater environments with abundant lighting. This perennial herb has a unique characteristic of floating above the water’s surface but can also establish roots in shallow water. Several studies showed that the roots of L. laevigatum have high removal efficiencies of heavy metals in wasted water up to a concentration of 70%, particularly Zn. However, the investigation of L. laevigatum to treat microorganisms in contaminated water still needs to be explored. After serial dilution, a lake water sample was isolated to identify the types of microbes. Gram-staining was applied as a preliminary analysis for further identification of the types of microbes by observing under a compound microscope. Following identification, 6 gram-positive and 4 gram-negative bacteria were tested with different amounts of L. laevigatum powder, 0.1 g, 0.2 g, and 0.3 g using a mass spectrophotometer to determine the effectiveness of inhibiting the growth of selected microbes. Gram-staining revealed that 66% of isolates are categorized as gram-positive bacteria, while 34% are gram-negative. Further observation shows that 75.75% of isolates from gram-positive bacteria are bacillus-shaped, and 24.25% are cocci-shaped among all gram-positive. 0.1 g of powder shows the least effect on inhibiting Gram-positive bacteria growth, whereas 0.3 g of powder shows the most impact on bacteria. Graphs with standard deviation (SD) values were plotted to compare the effectiveness between different concentrations of L. laevigatum and the differences between Gram-positive and Gram-negative bacteria. The antimicrobial properties of L. laevigatum show minimal effect on Gram-negative than Gram-positive bacteria. This research aims to assess the efficacy of L. laevigatum for inhibiting microbes’ growth, offering practical applications for sustainable water treatment, contributing to eco-friendly solutions, and promoting environmental sustainability.