Swiss Cheese Niche: Difference between revisions
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Lactobacillus helveticus is mainly involved with Streptococcus thermophilus in controlling the pH level of the Swiss cheese environment through their fermentation of lactose. The Swiss cheese enivronment changes temperatures due to the pastuerization process and in its intial stages Streptococcus thermophilus is the more dominant bacteria in the cheese. However since makers of Swiss cheese allow it to sit at room temperature for the ripening process allows for the growth of lactobacillus helveticus. Since room temperature is slightly off from the optimum growth temperature which is around 45 degrees Celcius for lactobacillus helveticus, the microbe is slowly able to grow. When L. helveticus reaches its maximum growth or reaches the stationary phase it begins to lyse and starts to affect the viability of Streptococcus thermophilus. There is correlation between the survivability of Lactobacillus and Streptococcus but there are no specifics as to why the correlations occur. [2] | Lactobacillus helveticus is mainly involved with Streptococcus thermophilus in controlling the pH level of the Swiss cheese environment through their fermentation of lactose. The Swiss cheese enivronment changes temperatures due to the pastuerization process and in its intial stages Streptococcus thermophilus is the more dominant bacteria in the cheese. However since makers of Swiss cheese allow it to sit at room temperature for the ripening process allows for the growth of lactobacillus helveticus. Since room temperature is slightly off from the optimum growth temperature which is around 45 degrees Celcius for lactobacillus helveticus, the microbe is slowly able to grow. When L. helveticus reaches its maximum growth or reaches the stationary phase it begins to lyse and starts to affect the viability of Streptococcus thermophilus. There is correlation between the survivability of Lactobacillus and Streptococcus but there are no specifics as to why the correlations occur. [2] | ||
The growth of P. Shermanii is heavily dependent on L. helveticus and S. thermophilus. Since low pH level does not favor growth for P. Shermanii, the ability of L. helveticus and S. thermophilus to change the pH of the niche determines the population size of P. Shermanii. Additionally, the bacterium relies on L. helveticus and S. thermophilus to produce lactic acid for it to consume. If lactic acid is not present, P. Shermanii can still survive by consuming lactose but the growth rate of the bacterium will be slower. | |||
===Do the microbes change their environment?=== | ===Do the microbes change their environment?=== | ||
Revision as of 13:55, 28 August 2008
Description of Niche
Where located?
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?
You may refer to organisms by genus or by genus and species, depending upon how detailed the your information might be. If there is already a microbewiki page describing that organism, make a link to it.
Within the Swiss Cheese environment lives three types of microbes of the genus lactobacillus, streptococcus, and propionibacteria.
Lactobacillus is a homofermentative and gram-positive bacteria that is always found within Swiss cheese due to its ability to provide texture and sharpness of the cheese. Different types of strains of lactobacillus(L. helveticus, L. casei, L. bulgaricus) live in Swiss cheese but the more commonly known bacteria is the strain lactobacills helveticus. This microbe is part of the lactic acid family of bacteria by converting lactose present in the cheese to lactic acid. [1]
S. Thermophilus is a homofermentative and gram-positive bacterium responsible for the initial lactate fermentation of Swiss cheese. S. Thermophilus is responsible for the acidity and texture in the cheese’s early production and involvement in lactic acid formation.
Propionibacterium Shermanii is a slow growing and gram positive bacterium that grows in an anaerobic glucose medium. P. shermanii is responsible for producing the holes and the distinct flavor of Swiss cheese. The growth rate of the bacterium is dependent on the surrounding temperature, pH, and bacteria. The optimal growth for P. shemanii is in warm temperature and at a pH of 5.3. The bacterium’s growth is also dependent of the availability of lactic acid which is produced by L. helveticus and S. thermophilus.
Do the microbes that are present interact with each other?
Describe any negative (competition) or positive (symbiosis) behavior
Lactobacillus helveticus is mainly involved with Streptococcus thermophilus in controlling the pH level of the Swiss cheese environment through their fermentation of lactose. The Swiss cheese enivronment changes temperatures due to the pastuerization process and in its intial stages Streptococcus thermophilus is the more dominant bacteria in the cheese. However since makers of Swiss cheese allow it to sit at room temperature for the ripening process allows for the growth of lactobacillus helveticus. Since room temperature is slightly off from the optimum growth temperature which is around 45 degrees Celcius for lactobacillus helveticus, the microbe is slowly able to grow. When L. helveticus reaches its maximum growth or reaches the stationary phase it begins to lyse and starts to affect the viability of Streptococcus thermophilus. There is correlation between the survivability of Lactobacillus and Streptococcus but there are no specifics as to why the correlations occur. [2]
The growth of P. Shermanii is heavily dependent on L. helveticus and S. thermophilus. Since low pH level does not favor growth for P. Shermanii, the ability of L. helveticus and S. thermophilus to change the pH of the niche determines the population size of P. Shermanii. Additionally, the bacterium relies on L. helveticus and S. thermophilus to produce lactic acid for it to consume. If lactic acid is not present, P. Shermanii can still survive by consuming lactose but the growth rate of the bacterium will be slower.
Do the microbes change their environment?
Do they alter pH, attach to surfaces, secrete anything, etc. etc.
The decrease in pH is attributed to the utilization of lactose and galactose during early stages of Swiss cheese manufacture. S. thermophilus and Lactobacillus alter the pH by fermenting the lactose that surrounds them and converting it into lactic acid. In addition to changing their environment Lactobacillus can also produce formation of lactate calcium crystals and toxic amines. The lactate calcium crystals form on the surfaces on the cheese and has no adherent effects on the Lactobacillus and is just a defect within the cheese environment. No information or study has been found yet on how the production of toxic amines would affect the surrounding microbes of Streptococcus and Propionibacteria but was more commonly known as an outbreak of food poisoning when ingested by humans. [3][4]
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.
Lactobacillus ferments lactose into lactic acid. Also among fermentation lactobacillus also has other metabolism such as
Current Research
Resistance to Freezing and Frozen Storage of Streptococcus thermophilus Is Related to Membrane Fatty Acid Composition
S. thermophilus’s ability to resist freezing and frozen storage was examined under four experimental factors and quantified by the ability to regain acidification activity of the lactic acid bacteria. The four experimental factors observed include: concentration of fatty acid with storage time, addition of glycerol as a cyroprotective agent, addition of oleic acid, and fermentation pH. The lactic acid bacteria was grown at 42C until the beginning of stationary phase at which experimental conditions were implemented. The acidification activity was measured before, after and during storage with the Cinac System. Experimental results show recovery of acidification activity of S. thermophilus with observable changes in membrane fatty acid composition with the experimental factors: increase in unsaturated fatty acid concentration with storage time, increase in unsaturated:saturated fatty acid ratio with addition of oleic acid and pH fermentation, but no effect in the addition of glycerol. The adaptation in unfavorable pH triggered a homeostatic mechanism that affected transbilayer movement of phospholipids and maintained permeability of membrane. The dependence of fermentation pH and oleic acid in unsaturated:saturated ratio still remains unclear [7]
References
[4] Hutkins, R., Halambeck, S. M., Morris, H. A. Use of Galactose-Fermenting Streptococcus thermophilus in the Manufacture of Swiss, Mozzarella, and Short-Method Cheddar Cheese J. Dairy Sci. 1986 69: 1-8
[7] Beal, C., Fonseca, F., Corrieu, G. Resistance to Freezing and Frozen Storage of Streptococcus thermophilus Is Related to Membrane Fatty Acid Composition. J. Dairy Sci. 2001 84: 2347-2356
Edited by Heidi Cung, Derrick Low, Binh Phung, and Danny Tran, students of Rachel Larsen
