Lactobacillus acidophilus: Difference between revisions

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=== Metabolism ===

[[File:Lactic acid fermentation.png|thumb|Pathway by which glucose is converted to lactic acid as a means of energy production]]

''L. acidophilus'' is a homofermentative anaerobic microorganism, meaning it only produces lactic acid as an end product of fermentation; and that it can only ferment hexoses (not pentoses) by way of the [[Glycolysis|EMP pathway]] (glycolysis).~~<ref name=":02" />~~ ''L. acidophilus'' has a slower growth time in milk than when in a host due to limited available nutrients. Because of its use as a probiotic in milk, a study done by the American ''Journal of Dairy Science'' examined the nutrient requirements of ''L. acidophilus'' in an effort to increase its low growth rate. The study found that [[glucose]] and the amino acids [[cysteine]], [[glutamic acid]], [[isoleucine]], [[leucine]], [[lysine]], [[methionine]], [[phenylalanine]], [[threonine]], [[tyrosine]], [[valine]], and [[arginine]] are essential nutrients to the growth of ''L. acidophilus'', with [[glycine]], calcium-pantothenate, and Mn<sup>2+</sup> acting as stimulatory nutrients. The study helps to explain the low growth rate of ''L. acidophilus'' in milk, as some of the amino acids necessary to ''L. acidophilus'' growth are lacking in milk. Adding amino acids with high rates of consumption to fermented milk is a possible solution to the problem.

''L. acidophilus'' is a homofermentative anaerobic microorganism, meaning it only produces lactic acid as an end product of fermentation; and that it can only ferment hexoses (not pentoses) by way of the [[Glycolysis|EMP pathway]] (glycolysis). ''L. acidophilus'' has a slower growth time in milk than when in a host due to limited available nutrients. Because of its use as a probiotic in milk, a study done by the American ''Journal of Dairy Science'' examined the nutrient requirements of ''L. acidophilus'' in an effort to increase its low growth rate. The study found that [[glucose]] and the amino acids [[cysteine]], [[glutamic acid]], [[isoleucine]], [[leucine]], [[lysine]], [[methionine]], [[phenylalanine]], [[threonine]], [[tyrosine]], [[valine]], and [[arginine]] are essential nutrients to the growth of ''L. acidophilus'', with [[glycine]], calcium-pantothenate, and Mn<sup>2+</sup> acting as stimulatory nutrients. The study helps to explain the low growth rate of ''L. acidophilus'' in milk, as some of the amino acids necessary to ''L. acidophilus'' growth are lacking in milk. Adding amino acids with high rates of consumption to fermented milk is a possible solution to the problem.

=== Genomics ===

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== Environment ==

[[File:Epithelial Tissues Simple Columnar Epithelium (41006485014).jpg|thumb|Columnar epithelial cells from a mammal's intestinal tract. ''L. acidophilus'' easily adheres to and commonly grows on this cell type]]

''L. acidophilus'' grows naturally in the oral, intestinal, and vaginal cavities of mammals. Nearly all Lactobacillus species have special mechanisms for heat resistance which involves enhancing the activity of [[Chaperone (protein)|chaperones]]. Chaperones are highly conserved stress proteins that allow for enhanced resistance to elevated temperatures, ribosome stability, temperature sensing, and control of ribosomal function at high temperatures. This ability to function at high temperatures is extremely important to cell yield during the fermentation process, and [[genetic testing]] on ''L. acidophilus'' in order to increase its temperature tolerance is currently being done. When being considered as a probiotic, it is important for ''L. acidophilus'' to have traits suitable for life in the gastrointestinal tract. Tolerance of low pH and high toxicity levels are often required. These traits vary and are strain specific. Mechanisms by which these tolerances are expressed include differences in cell wall structure, along with other changes is protein expression.~~<ref name=":5" />~~ Changes in salt concentration have been shown to affect ''L. acidophilus'' viability, but only after exposure to higher salt concentrations. In another experiment highlighted by the American Dairy Science Association, viable cell counts only showed a significant reduction after exposure to NaCl concentrations of 7.5% or higher. Cells were also observed to distinctly elongate when grown in conditions of 10% NaCl concentration or higher.~~<ref name=":8" />~~ ''L. acidophilus'' is also very well suited for living in a dairy medium, as fermented milk is the ideal method of delivery for introducing ''L. acidophilus'' into a gut microbiome.~~<ref name=":63"/>~~ The viability of ''L. acidophilus'' cells encapsulated by spray drying technology stored at refrigerated condition (4 °C) is higher than the viability of cells stored at room temperature (25 °C).

''L. acidophilus'' grows naturally in the oral, intestinal, and vaginal cavities of mammals. Nearly all Lactobacillus species have special mechanisms for heat resistance which involves enhancing the activity of [[Chaperone (protein)|chaperones]]. Chaperones are highly conserved stress proteins that allow for enhanced resistance to elevated temperatures, ribosome stability, temperature sensing, and control of ribosomal function at high temperatures. This ability to function at high temperatures is extremely important to cell yield during the fermentation process, and [[genetic testing]] on ''L. acidophilus'' in order to increase its temperature tolerance is currently being done. When being considered as a probiotic, it is important for ''L. acidophilus'' to have traits suitable for life in the gastrointestinal tract. Tolerance of low pH and high toxicity levels are often required. These traits vary and are strain specific. Mechanisms by which these tolerances are expressed include differences in cell wall structure, along with other changes is protein expression. Changes in salt concentration have been shown to affect ''L. acidophilus'' viability, but only after exposure to higher salt concentrations. In another experiment highlighted by the American Dairy Science Association, viable cell counts only showed a significant reduction after exposure to NaCl concentrations of 7.5% or higher. Cells were also observed to distinctly elongate when grown in conditions of 10% NaCl concentration or higher. ''L. acidophilus'' is also very well suited for living in a dairy medium, as fermented milk is the ideal method of delivery for introducing ''L. acidophilus'' into a gut microbiome. The viability of ''L. acidophilus'' cells encapsulated by spray drying technology stored at refrigerated condition (4 °C) is higher than the viability of cells stored at room temperature (25 °C).

=== Quorum sensing ===

@@ Line 27: / Line 27: @@
 === Metabolism ===
 [[File:Lactic acid fermentation.png|thumb|Pathway by which glucose is converted to lactic acid as a means of energy production]]
-''L. acidophilus'' is a homofermentative anaerobic microorganism, meaning it only produces lactic acid as an end product of fermentation; and that it can only ferment hexoses (not pentoses) by way of the [[Glycolysis|EMP pathway]] (glycolysis).<ref name=":02" /> ''L. acidophilus'' has a slower growth time in milk than when in a host due to limited available nutrients. Because of its use as a probiotic in milk, a study done by the American ''Journal of Dairy Science'' examined the nutrient requirements of ''L. acidophilus'' in an effort to increase its low growth rate. The study found that [[glucose]] and the amino acids [[cysteine]], [[glutamic acid]], [[isoleucine]], [[leucine]], [[lysine]], [[methionine]], [[phenylalanine]], [[threonine]], [[tyrosine]], [[valine]], and [[arginine]] are essential nutrients to the growth of ''L. acidophilus'', with [[glycine]], calcium-pantothenate, and Mn<sup>2+</sup> acting as stimulatory nutrients. The study helps to explain the low growth rate of ''L. acidophilus'' in milk, as some of the amino acids necessary to ''L. acidophilus'' growth are lacking in milk. Adding amino acids with high rates of consumption to fermented milk is a possible solution to the problem.
+''L. acidophilus'' is a homofermentative anaerobic microorganism, meaning it only produces lactic acid as an end product of fermentation; and that it can only ferment hexoses (not pentoses) by way of the [[Glycolysis|EMP pathway]] (glycolysis). ''L. acidophilus'' has a slower growth time in milk than when in a host due to limited available nutrients. Because of its use as a probiotic in milk, a study done by the American ''Journal of Dairy Science'' examined the nutrient requirements of ''L. acidophilus'' in an effort to increase its low growth rate. The study found that [[glucose]] and the amino acids [[cysteine]], [[glutamic acid]], [[isoleucine]], [[leucine]], [[lysine]], [[methionine]], [[phenylalanine]], [[threonine]], [[tyrosine]], [[valine]], and [[arginine]] are essential nutrients to the growth of ''L. acidophilus'', with [[glycine]], calcium-pantothenate, and Mn<sup>2+</sup> acting as stimulatory nutrients. The study helps to explain the low growth rate of ''L. acidophilus'' in milk, as some of the amino acids necessary to ''L. acidophilus'' growth are lacking in milk. Adding amino acids with high rates of consumption to fermented milk is a possible solution to the problem.
 === Genomics ===
@@ Line 34: / Line 34: @@
 == Environment ==
 [[File:Epithelial Tissues Simple Columnar Epithelium (41006485014).jpg|thumb|Columnar epithelial cells from a mammal's intestinal tract. ''L. acidophilus'' easily adheres to and commonly grows on this cell type]]
-''L. acidophilus'' grows naturally in the oral, intestinal, and vaginal cavities of mammals. Nearly all Lactobacillus species have special mechanisms for heat resistance which involves enhancing the activity of [[Chaperone (protein)|chaperones]]. Chaperones are highly conserved stress proteins that allow for enhanced resistance to elevated temperatures, ribosome stability, temperature sensing, and control of ribosomal function at high temperatures. This ability to function at high temperatures is extremely important to cell yield during the fermentation process, and [[genetic testing]] on ''L. acidophilus'' in order to increase its temperature tolerance is currently being done. When being considered as a probiotic, it is important for ''L. acidophilus'' to have traits suitable for life in the gastrointestinal tract. Tolerance of low pH and high toxicity levels are often required. These traits vary and are strain specific. Mechanisms by which these tolerances are expressed include differences in cell wall structure, along with other changes is protein expression.<ref name=":5" /> Changes in salt concentration have been shown to affect ''L. acidophilus'' viability, but only after exposure to higher salt concentrations. In another experiment highlighted by the American Dairy Science Association, viable cell counts only showed a significant reduction after exposure to NaCl concentrations of 7.5% or higher. Cells were also observed to distinctly elongate when grown in conditions of 10% NaCl concentration or higher.<ref name=":8" /> ''L. acidophilus'' is also very well suited for living in a dairy medium, as fermented milk is the ideal method of delivery for introducing ''L. acidophilus'' into a gut microbiome.<ref name=":63"/> The viability of ''L. acidophilus'' cells encapsulated by spray drying technology stored at refrigerated condition (4&nbsp;°C) is higher than the viability of cells stored at room temperature (25&nbsp;°C).
+''L. acidophilus'' grows naturally in the oral, intestinal, and vaginal cavities of mammals. Nearly all Lactobacillus species have special mechanisms for heat resistance which involves enhancing the activity of [[Chaperone (protein)|chaperones]]. Chaperones are highly conserved stress proteins that allow for enhanced resistance to elevated temperatures, ribosome stability, temperature sensing, and control of ribosomal function at high temperatures. This ability to function at high temperatures is extremely important to cell yield during the fermentation process, and [[genetic testing]] on ''L. acidophilus'' in order to increase its temperature tolerance is currently being done. When being considered as a probiotic, it is important for ''L. acidophilus'' to have traits suitable for life in the gastrointestinal tract. Tolerance of low pH and high toxicity levels are often required. These traits vary and are strain specific. Mechanisms by which these tolerances are expressed include differences in cell wall structure, along with other changes is protein expression. Changes in salt concentration have been shown to affect ''L. acidophilus'' viability, but only after exposure to higher salt concentrations. In another experiment highlighted by the American Dairy Science Association, viable cell counts only showed a significant reduction after exposure to NaCl concentrations of 7.5% or higher. Cells were also observed to distinctly elongate when grown in conditions of 10% NaCl concentration or higher. ''L. acidophilus'' is also very well suited for living in a dairy medium, as fermented milk is the ideal method of delivery for introducing ''L. acidophilus'' into a gut microbiome. The viability of ''L. acidophilus'' cells encapsulated by spray drying technology stored at refrigerated condition (4&nbsp;°C) is higher than the viability of cells stored at room temperature (25&nbsp;°C).
 === Quorum sensing ===