Spoiled meat niche

Description of Niche

Physical Conditions?

What are the conditions in your niche? Temperature, pressure, pH, moisture, etc.

Influence by Adjacent Communities (if any)

Is your niche close to another niche or influenced by another community of organisms?

Conditions under which the environment changes

Do any of the physical conditions change? Are there chemicals, other organisms, nutrients, etc. that might change the community of your niche.

Who lives there?

Which microbes are present?

Brochotrix thermosphacta

Carnobacterium

Clostridium [[1]]

Enterobacterium

Lactobacillus [[2]]

Leuconostoc [[3]] Leuconostoc is one of the lactic acid bacteria; it produces D-lactate and ethanol. This group of microbe is responsible for the discoloration, gas production, and buttery smell of spoiled meat. [1] The genus Leuconostoc is described as being spherical cells that is gram-positive and often lenticular on agar. This bacterium grows optimally in an environment of 20-30°C. However, they also require a rich and complex media for growth. A rich and complex media includes nicotinic acid, thiamin, biotin, and pantothenic acid. For energy, they are heterofermentatives, which means they use a combination of pentose phosphate and phosphoketolase pathways. This microbe cannot go through spore formation for survive. Leuconostoc was originally placed into Streptococcaceae bacteria family as mentioned in Bergey’s Manual of Determinative Bacteriology. However, in 1986, the Bergey’s Manual of Systematic Bacteriology moved Leuconostoc from the Streptococcaceae family into the Deinococcaceae family. [7]

Pseudomonas [[4]]

Shewanella putrefaciens

Do the microbes change their environment?

Brochothrix thermosphacta, Carnobacterium spp., Enterobacteriaceae, Lactobacillus spp., Leuconostoc spp., Pseudomonas spp., Shewanella putrefaciens and Weissella spp. work together to create the spoiled meat profile: discoloration, gas production, slime production, decrease in pH, and sour off-flavor. [2]

Clostridium work with lactic acid bacterias to produce large amounts of gas (H2 and CO2) which is accompanied by a foul odor. [2]

Do the microbes carry out any metabolism that affects their environment?

Do they ferment sugars to produce acid, break down large molecules, fix nitrogen, etc. etc.

Current Research

In lactic acid bacteria associated with vacuum-packed cooked meat product spoilage: population analysis by rDNA-based methods (2006), investigators aimed to research and find which lactic acid bacteria was involved in the spoilaged of vacuum packaged cooked meat products. They did this by studying different samples of bacteria within 4 meat products, some of which had spoilage symptons, some that did not. Colonies of these were then grown on yeast glucose lactose peptone and trypticase soy yeast plates, and where then identifived via internal spacer region. The study found that Leuc. Mesenteroides was the main spoilage agent within vacuum packaged meats. The significance of this study was to determine what organisms to look for to prevent the spoilage of vacuum packaged meats. [1]

Development of a Microbial Model for the Combined Effect of Temperature and pH on Spoilage of Ground Meat, and Validation of the Model under Dynamic Temperature Conditions (2005). The study aimed at using microbiological and sensory analysis at predicting spoilage of aerobic stored ground meat. Under aerobic conditions, samples of ground meat (beef and pork) were analyzed for changes in their appearances, smells and microbes composition at certain pH (5.34-6.13) and temperature (0-20 Celcius). As observed, pseudomonads were the predominant bacteria isolated. In addition, it was also detected that the changes in pseudonomads populations is proportional to the sensory changes. Thus, microbiological and sensory analysis can be used as a “good index for spoilage of aerobically stored ground meat”. Following this type of model, the meat industry can benefit from by running more “effective management systems, which will optimize the quality of meat products”. [3 JN]

References

[1] Chenoll, E., Macian, M., Elizaquivel, P., Aznar, R. "Lactic Acid Bacteria Associated with Vacuum-packed Cooked Meat Product Spoilage: Population Analysis by rDNA-based Methods". Journal of Applied Microbiology. 2006. Volume 102. p. 498-508.

[2] Borch, E., Kant-Muermans, M., Blixt, Y. "Bacterial Spoilage of Meat and Cured Meat Products". International Journal of Food Microbiology". 1996. Volume 33. p. 103-120.

[3] Koutsoumanis, K., A. Stamatiou, P. Skandamis, and G.-J. E. Nychas. 2005. Development of a Microbial Model for the Combined Effect of Temperature and pH on Spoilage of Ground Meat, and Validation of the Model under Dynamic Temperature Conditions. Applied and Environmental Microbiol. 72: 124-134. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1352189

Edited by [Steven Lee , Jade Nguyen , Ngoc-minh Nguyen , Sarah Paek , June Tse , Amy Vo], students of Rachel Larsen