Degradation of agar by a gram-negative bacterium

Area of Science:

• Microbiology
• Biochemistry

Background:

• Agar and agarose are widely used polysaccharides in various scientific applications.
• The microbial degradation of agar is of interest for biotechnological and environmental purposes.

Purpose of the Study:

• To isolate and characterize a novel agar-degrading bacterium from sewage.
• To investigate the properties and release of the agarase enzyme.

Main Methods:

• Isolation of bacteria from sewage samples.
• Cultivation in a simple salts medium with carbohydrates.
• Assay of agar and agarose degradation using gels and suspensions.
• Determination of agarase location (cell-bound vs. released) during bacterial growth phases.
• Analysis of enzyme activity using cell extracts and culture filtrates.

Main Results:

• An agar-degrading, Gram-negative bacterium with 50.5 mol% guanine-cytosine content was isolated.
• The bacterium efficiently degraded agar and agarose gels and suspensions but not cross-linked variants.
• Agarase was cell-bound during exponential growth and released into the medium at the stationary phase.
• Cell extracts and culture filtrates reduced agar's gelling ability and turbidity, indicating enzymatic breakdown.

Conclusions:

• A novel, sewage-derived bacterium possesses significant agarolytic activity.
• The agarase enzyme is released extracellularly during the stationary phase of bacterial growth.
• This enzyme effectively depolymerizes agar and agarose, reducing their gelling and structural properties.