Karakterisasi Isolat Bakteri Asal Danau dan Analisis Toleransi terhadap Hidrogen Sulfida (H2S) berdasarkan Pertumbuhan dan Respons Fisiologis

Abstract

Hidrogen sulfida (H2S) senyawa sulfur tereduksi yang dapat mempengaruhi aktivitas fisiologis mikroorganisme. Penelitian ini bertujuan mengaraktrisasi isolat bakteri asal danau serta mengetahui kemampuan toleransi terhadap H2S, berdasarkan pertumbuhan dan respons fisiologis. Karakterisasi isolat diamati berdasarkan pengamatan morfologi, pewarnaan Gram, dan identifikasi molekuler 16S rRNA. Analisis toleransi dilakukan pada media Tryptic Soy Broth + monosodium glutamat 1% yang ditambahkan Na2S dengan konsentrasi 10, 50, dan 100 µg/ml, dengan masa inkubasi 72 jam. Hasil karakterisasi isolat S3 memiliki koloni berwarna merah, bentuk circular, tepian entire, elevasi convex, tekstur halus berlendir, serta sel berbentuk batang pendek dan bertipe Gram negatif. Analisis sekuens gen 16S rRNA memiliki kemiripan 98.95% dengan Serratia marcescens subsp. marcescens dan didukung dengan analisis filogenetik dengan nilai boostrap 99. Hasil pengujian H2S menunjukan isolat mampu tumbuh pada semua Perlakuan H2S hingga konsentrasi 100 µg/ml yang ditandai dengan kekeruhan dan pigmen kembali muncul ketika isolat ditumbuhkan kembali pada media tanpa H2S. Hasil penelitian menunjukan S. marcescens subsp. marcescens isolat S3 memiliki kemampuan toleransi terhadap H2S hingga konsentrasi 100 µg/ml, tetapi mengalami perubahan respons fisiologis berupa hambatan sementara produksi pigmen merah pada bakteri.

Hydrogen sulfide (H2S) is a reduced sulfur compound that can effect the physiological activity of microorganisms. This study aims to characterize bacterial isolates from lakes and to determine their tolerance to H2S based on growth and physiological responses. The characterization of the isolates was based on morphological observation, Gram staining, and 16S rRNA molecular identification. Tolerance analysis was conducted on TSB+MSG medium supplemented with Na2S at concentrations of 10, 50, and 100 µg/ml, with an incubation period of 72 hours. The characterization result showed that isolate S3 had red colored colonies that were circular in shape, with entire margins, a convex elevation, a smooth, slimy texture, and short rod shaped, Gram negative cells. Sequencing of the 16S rRNA gene revealed 98.95% similarity to Serratia marcescens subsp. marcescens, a finding supported by phylogenetic analysis with a boostrap value 99. Test results showed that the isolate was able to grow under all H2S treatments up to a concentration off 100 µg/ml, as indicated by turbidity and the reappearance of pigment when the isolate was regrown on H2S free medium. The results of the study indicate that the S. marcescens subsp. marcescens isolate S3 exhibits tolerance to H2S up to a concentration of 100 µg/ml, but experiences a physiological response in the form of a temporary inhibition of red pigment production in the bacteria.