Diversity and anaerobic growth of Pseudomonas spp. isolated from modified atmosphere packaged minced beef

This study aimed to monitor development of spoilage-associated microbiota on high-oxygen modified atmosphere packaged (MAP) minced beef, assess diversity of Pseudomonas sp. therein employing a polyphasic approach and probe their ability to grow anaerobically in the presence of carbon dioxide.

Headspace atmosphere and total viable count of MAP minced beef were monitored, and spoilage-associated microbiota was identified using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). Pseudomonas spp. represented a major part of the spoilage-associated microbiota throughout the spoilage process and were characterized with a polyphasic approach including MALDI-TOF, randomly amplified polymorphic DNA biotyping, 16S rDNA and rpoD sequence analysis, and carA multiplex polymerase chain reaction. Pseudomonas isolates displayed high diversity and varying assertiveness under conditions employed in MAP minced beef with P. fragi, P. lundensis and P. weihenstephanensis as dominant species.

The polyphasic approach enabled high-throughput characterization of Pseudomonas sp. Their adapted capability to grow anaerobically and resistance to high levels of CO₂ is suggested to be a general feature within the genus, which is hitherto underexplored.

This study shows that diverse Pseudomonas generally regarded as strict aerobes and CO₂ -sensitive appear well adapted to grow under MAP conditions, leading to high cell counts in minced beef and ultimately contribute to spoilage of the product.