![]() ![]() Protection or repair of macromolecules such as DNA and proteins as essential acid resistance mechanism has also been described by several researchers 3, 6, 7. Examples of these systems include lysine, arginine, and glutamate decarboxylases that combine a proton with internalized amino acid (lysine, arginine, or glutamate) and exchange the product for another amino acid 5. The role of amino acid decarboxylases in maintaining bacterial pH homeostasis has also been reported 4. The changes in membrane fatty acid profiles in response to dropping in pH point out the significant role of the cell membrane in acid tolerance 3. Survival and growth under stress involve changes in cell structure, metabolism, and transport patterns (F1F0-ATPase, ABC transporter). Neutralophilic bacteria adopt a number of mechanisms in maintaining pH homeostasis including no growth strategy as adopted by Escherichia coli and Salmonella spp., to survive during exposure to pH values that are outside their growth range 1, 2. ![]() The importance of acid stress has propelled several studies in unraveling the molecular mechanisms of acid tolerance in bacteria especially the pathogenic enteric bacteria and those involved with food and beverages. Acidic stress condition specifically, soil acidic condition has significant relevance and ramification in agriculture, food, and human health. Hope you enjoyed this topic and see you next week for more exciting pictures of microorganisms.Bacteria have innate ability to survive and grow in several stress conditions including extreme ecological niches. ![]() ![]() From this information, it can be said that the bacterial cells that contain endospores inside of the cell have received some kind of environmental stress, while the free endospores are dormant and the bacterial cells without the endospores have not received environmental stress. The endospores will stay remain inactive until a bacterial cell needs it again as a result of environmental stress. Once the bacteria relieves itself of environmental stress, the endospores get released from the bacterial cell and the cell itself will be destroyed. When these bacteria receive stress from the environment that limits their growth, they begin to form endospores from vegetative cells. So what's the importance of these so called endospores? Well for Bacillus megaterium, it is use as a survival mechanism. Then there are a few endospores that remained inside the bacterial cells. These free endospores above appear to be a cluster of two rather large endospores. When looking at the picture above you can see that some spores are outside the cells which are commonly known as free endospores. This lets us know exactly where each cell is and whether or not the endospores are inside the cells or outside. This process allows us to see the endospores in green while the cells appear pink. There was no discoloration process, commonly performed in differential staining, for spore staining. In spore staining, Malachite green dye was used to stain the endospores as well as Safranin, commonly used in Gram staining, was used to stain the cells. This week in microbiology lab we spore stained Bacillus megaterium shown above at 1000x (1000 times) more than what we can see with the naked eye. ![]()
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