Anti-Microbial Activities of Shallots (Allium cepa L.) Extract and Garlic (Allium sativum L.) Extract on the Growth of Peat Soil Bacteria

This study aims to examine the antimicrobial activity of shallots (Allium cepa L.) and garlic (Allium sativum L.) extracts on the growth of peat soil bacteria. This type of research is an experimental study using a Completely Randomized Design with four levels of treatment. Test for bacterial activity using the agar diffusion method with the paper disc technique. Data were analyzed statistically using One Way ANOVA and the Games-Howell post-hoc test at the 5% significance level. The results showed that shallots (Allium cepa L.) and garlic (Allium sativum L.) extracts had antimicrobial activity against the growth of tested bacteria as indicated by the presence of a clear zone as an indicator of inhibition of bacterial growth. Garlic has better antimicrobial activity seen from the diameter of the clear zone that appears in the garlic extract treatment ranging from 8-13 mm, whereas in the treatment of onions it ranges from 3–5 mm.


Introduction
Prevention or treatment of diseases caused by pathogenic bacteria usually uses compounds that have antimicrobial activity. Antimicrobial compounds are compounds that can inhibit or interfere with microbial growth and metabolism (Cowan, 1999); (Sartelli et al., 2016); (Asif, 2017). Terms such as anti-bacterial or anti-fungal are used for antimicrobial compounds that inhibit specific groups of microbes, namely anti-bacteria for bacteria and anti-fungal for fungi. Two mechanisms are primarily due to the antibacterial behavior of an agent, which involves chemically interfering with the synthesis or function of essential components of bacteria and/or circumventing traditional antibacterial resistance mechanisms (Amerikova et al., 2019;Gonelimali et al., 2018;Khameneh et al., 2019). There are many targets for antibacterial agents, including bacterial protein biosynthesis; bacterial cell-wall biosynthesis; degradation of bacterial cell membranes; replication and repair of bacterial DNA; and inhibition of a metabolic pathway (Khameneh et al., 2019).
Several studies have examined the diversity and composition of soil microbial populations, including peat soils (Mandic-Mulec et al., 2014). Peat soils are rich in bacterial communities that help fertilize the soil as a denitrifier that is involved in denitrification and nitrogen fixer (Kusai & Ayob, 2020). Pathogenic bacteria are also found in the peat soils, such as Bacillus anthracis that is known as a pathogen that infects humans, wildlife, and livestock (Irenge & Gala, 2012;Wall et al., 2015). This study aims to examine the antimicrobial activity of shallot extract (Allium cepa L.) and garlic extract (Allium sativum L.) on the growth of peat soil bacteria.

Materials
The tested bacteria in this experiment were bacteria isolated from peat soil on Jl. Mahir Mahar, Palangka Raya, Central Kalimantan. Soil samples were diluted by serial dilution method and then planted on NA (Nutrient Agar) media as culture stock. The instruments and materials used in this study are presented in Table 1 and Table 2.  Alcohol 70% Sufficiently 7 Paper Sufficiently 8 Latex Gloves 1 pair 9 Cotton Sufficiently

Methods
This study used a completely randomized design with 4 levels of treatment and 4 replications ( Table 3). Consisting of 4 groups, namely two control groups (positive control and negative control) and two treatment groups.  c. Soaking the refined shallots (Allium cepa L.) and garlic (Allium sativum L.) in distilled water for 24 hours. d. After 24 hours, the soaking was filtered to obtain the extract of shallots (Allium cepa L.) and garlic (Allium sativum L.) with water solvent. b. Soak the paper disc (cut using a paper punch) in each solution.

Sterilization
c. Cover the solution with aluminum foil.

Anti-Microbial Activity Test
The anti-microbial activity was observed from the results of measurements of the clear zone/inhibition zone diameter at 24 hours and 48 hours after bacterial inoculation and treatment.

Data Analysis
The data obtained from each treatment level were analyzed using the One Way ANOVA formula at the 5% significance level. The data will be analyzed using the SPSS 23 program. The hypothesis in this study is as follows: H0 : Shallot extract (Allium cepa L.) and garlic extract (Allium sativum L.) do not have an antimicrobial activity that inhibits bacterial growth. H1 : Shallot extract (Allium cepa L.) and garlic extract (Allium sativum L.) have an antimicrobial activity that inhibits bacterial growth.
If the p-value <0.05, then H0 is rejected. This shows that there is a significant difference between treatments and to find out which treatment is the best, it is necessary to carry out post-hoc tests, namely the Bonferroni test (if the variance is homogeneous) and the Games-Howell test (if the variance is not homogeneous).

Results
The research data is in the form of measurements of the clear zone diameter which is an indicator of the presence of antimicrobial activity against bacteria. Measurements were carried out twice, precisely at 24 hours (24h) and 48 hours (48h) after the inoculation of the bacterial sample and the treatment. The data on the results of clear zone measurements at 24h and 48h are presented in Table 4, Table 5, and Figure 1. The results of the One Way ANOVA analysis on the 24h and 48h data using the SPSS program in Table 6 show that there is a significant difference (reject H0) at the 5%  Post-hoc tests were carried out to determine which treatment was the most ideal between T1 (onion extract) and T2 (garlic extract). The results of the homogeneity test showed that the p-value (sig.) Was 0.024 (24h) and 0.026 (48h) less than 0.05, which means that the data variance was not homogeneous. Then a further Games-Howell test was carried out using the SPSS 23 program with the detailed results presented in Table 7 and Table 8 which show that between Positive Control (C+) and Treatment 2 (T2) were not significantly different. This means that the inhibition (antimicrobial activity) of garlic extract (Allium sativum L.) is better than that of shallot extract (Allium cepa L.). The length of the clear zone diameter between treatments is presented in Figure 3. .5500* Significant

Discussion
Extracts of shallots (Allium cepa L.) and garlic (Allium sativum L.) have long been and are widely used as antimicrobials to inhibit the growth of bacteria, fungi, and other parasitic microorganisms. This study tested the antimicrobial activity of shallot (Allium cepa L.) and garlic (Allium sativum L.) extracts against tested bacteria. Bacterial

T1 T2
samples were obtained from peat soil and grown on NA media. The results showed that both extracts had antimicrobial activity against the growth of the tested bacterial colonies. This is indicated by the clear zone on the treated media and the results of the one-way ANOVA analysis (p-value 0.000 <0.050). Research by (Yousufi, 2012) dan (Zine & Zine, 2015) shows that onion extract and garlic extract have antimicrobial activity inhibiting the growth of E. coli, Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi, Aerobacter aerogenes, and Proteus vulgaricus.
Shallots (Allium cepa L.) contain many phytochemical compounds, most of which are hydrocarbons and their derivatives (Griffiths et al., 2002). Quercetin and allicin are the main components of shallots that act as antimicrobials, especially antibacterials (Shrestha et al., 2016), quercetin is bound to the bacterial enzyme DNA gyrase and allicin inhibits enzymes that contain thiol (Ankri & Mirelman, 1999). DNA gyrase is an essential bacterial enzyme that catalyzes ATP-dependent negative super-coiling of double-stranded closed-circular DNA, which is included in the topoisomerase enzyme group (Reece & Maxwell, 1991) (Papillon et al., 2013). Gyrase has a different affinity for various molecules, making it an ideal antibiotic target (Engle et al., 1982). Shallots also contain flavonoids and polyphenols which based on several research results show that these compounds have antibacterial activity (Hendrich, 2006) (Ani et al., 2006).
Garlic (Allium sativum) also contains many phytochemical compounds that have pharmaceutical effects, including allicin which is the most potent compound as an antibacterial agent (Shrestha et al., 2016).
The results of post hoc analysis using Games-Howell showed that garlic extract (Allium sativum L.) was not significantly different from the positive control (C+; Amoxicillin). This means that the inhibitory power of garlic extract against bacterial growth is almost the same as that of commercial antibiotics (Amoxicillin). The diameter of the clear zone (inhibition zone) of garlic extract ranged from 8-13 mm, larger than the diameter of the clear zone of shallot extract which ranged from 3-5 mm at the same concentration.
Shallot extract (Allium cepa L.) actively inhibits gram-positive bacteria but is weak against gram-negative bacteria (Kirilov et al., 2014). This suggests that the tested bacterial strains obtained from peat soil are thought to be gram-negative bacteria so that the inhibition (antimicrobial activity) of shallots decreases. (Shrestha et al., 2016) through research that has been conducted, concluded that the mixture of garlic extract is more potential as an antibacterial than red onion extract, even the mixture of garlic and onion (1:1) still shows better antimicrobial activity.

Conclusion
The conclusions of this study are: (1) shallot extract (Allium cepa L.) and garlic extract (Allium sativum L.) have antimicrobial activity against the growth of tested bacteria which is indicated by the presence of a clear zone as an indicator of growth inhibition. bacteria; and (2) Garlic has better antimicrobial activity seen from the diameter of the clear zone that appears in the garlic extract treatment ranging from 8 -13 mm, while in the treatment of onions it ranges from 3 -5 mm.