Related Experiment Videos
Observations by electron microscopy on pig muscle inoculated and incubated with Pseudomonas fragi
Abstract:
Myofibrils from pig muscle inoculated and incubated with Pseudomonas fragi showed an extremely disrupted appearance as compared to uninoculated controls. There was an almost complete absence of material in the H zone, marked disruption of the A band (probably myosin), and some loss of dense material from the Z line. These changes indicated that marked proteolysis had occurred. Bacteria observed in spoiled muscle tissue exhibited protrusions or blebs on the outer surface of the cell walls. The blebs appeared to form detached globules that migrated into the muscle mass. Bacteria grown in non-muscle-containing media did not produce blebs, which indicates the blebs were induced by growth on muscle tissue. The possibility that the blebs and globules may contain a proteolytic enzyme responsible for myofibrillar disruption is discussed.
Insights
Pseudomonas fragi causes significant muscle protein breakdown in pigs. Bacterial blebs, likely containing enzymes, are implicated in this myofibrillar disruption during spoilage.
Area of Science:
- Food microbiology
- Proteolysis
- Muscle biochemistry
Background:
- Pseudomonas fragi is a common spoilage bacterium in meat.
- Bacterial activity leads to meat spoilage and texture changes.
- Understanding the mechanisms of bacterial spoilage is crucial for food preservation.
Purpose of the Study:
- To investigate the effects of Pseudomonas fragi on pig muscle myofibrils.
- To identify potential mechanisms of bacterial-induced muscle proteolysis.
- To examine the role of bacterial structures in muscle degradation.
Main Methods:
- Inoculation of pig muscle myofibrils with Pseudomonas fragi.
- Microscopic examination of myofibrillar structure.
- Culturing bacteria in muscle and non-muscle media.
- Observation of bacterial cell surface structures.
Main Results:
- Pseudomonas fragi inoculation caused severe disruption of myofibrils, including the H zone, A band (myosin), and Z line.
- Marked proteolysis was evident in inoculated muscle tissue.
- Bacteria exhibited blebs on their cell walls, forming globules that migrated into muscle.
- Bleb formation was specific to growth on muscle tissue, suggesting induction by muscle components.
Conclusions:
- Pseudomonas fragi induces significant proteolysis and myofibrillar damage in pig muscle.
- Bacterial blebs, potentially containing proteolytic enzymes, are likely responsible for the observed muscle disruption.
- Further research is warranted to confirm the enzymatic activity of these blebs in meat spoilage.