Radiation-resistant Macrococcus caseolyticus (A) isolated from radiation-processed semidried prawns

Area of Science:

• Microbiology
• Food Science
• Radiation Biology

Background:

• Bacterial contamination in food processing is a significant concern.
• Gamma irradiation is used for food preservation, but radiation-resistant bacteria can survive.
• Macrococcus caseolyticus is a known bacterium, but its radiation resistance is not well-documented.

Purpose of the Study:

• To identify and characterize a radiation-resistant bacterial isolate from gamma-radiation-processed semidried prawns.
• To determine the radiation resistance profile of the identified isolate.
• To compare its resistance to other bacterial strains.

Main Methods:

• Isolation and identification of bacteria from irradiated prawns.
• Morphological and biochemical characterization.
• 16S rRNA sequencing and DNA-DNA hybridization.
• Fatty acid methyl ester analysis.
• Determination of decimal reduction dose (D10) for gamma radiation.

Main Results:

• A new strain of Macrococcus caseolyticus, designated M. caseolyticus (A), was identified.
• M. caseolyticus (A) showed significant resistance to gamma radiation, with a D10 of 1.18 kGy.
• The isolate was more resistant to gamma and UV radiation than M. caseolyticus JCSC5402 and Staphylococcus aureus MTCC96.
• Fatty acid profile analysis supported its classification as M. caseolyticus, though with notable differences.
• The strain demonstrated sensitivity to heat and desiccation stress.

Conclusions:

• Macrococcus caseolyticus (A) represents a novel, radiation-resistant strain.
• This finding has implications for understanding microbial survival in irradiated foods.
• Further research into the mechanisms of radiation resistance in M. caseolyticus (A) is warranted.