Microbial Powerhouses: Exploring the Roles of Yeast and Lactobacillus Acidophilus in Human Life

The world that we live in today is crowded with an army of bacteria and fungi that can immensely benefit and impact human life. Yeast and Lactobacillusacidophilus is no stranger in this field. These two microbes have been known to boast many benefits that prove to positively impact human life such as being vital ingredients in beer and yoghurt production. Lactobacillusacidophilus which is part of a family of lactic acid bacteria known as Lactobacillaceae can also be more commonly referred to as acidophilus.

Acidophilus is naturally found in our intestinal area acting as a positive bacteria, as it produces lactic acid to combat against harmful bacteria colonizing in our intestines.

Acidophilus is also common in many health supplements. Yeast, which is also known in Latinised Greek as SaccharomycesCerevisiae meaning ‘sugar-fungus’ and ‘beer’ also show traits that improve and positively impact human life. For example, yeast is an essential ingredient in bread production as it acts as a leavening agent to help the bread rise.

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Bread has been a staple in our diets for many centuries this would not have been possible if it weren't for yeast and the discoveries made allowing us to better understand and maximise the full potential of yeast as a leavening agent. Wine and beer are also huge beneficiaries of yeast as they rely on yeast in the fermentation process to allow them to become alcoholic beverages. We can clearly see that yeast and Lactobacillusacidophilus both positively impact human life. In my report below, I will be further elaborating on these two microbes.

There are approximately 1500 different types of yeast species which have slight structural variations and functions. Nevertheless, these single cellular fungi generally tend to share similar characteristics in their structure such as all having a nucleus, cell wall and a vacuole. The role of the nucleus within a yeast cell is to carry and transfer the genetics of the cell, this is especially crucial in the budding process, where the genetic material from the nucleus aids the yeast cell to reproduces by dividing into two individual cells. Moreover, the role of the cell wall within a yeast cell allows the cell to keep a rigid shape, while the vacuole is responsible for being the primary storage ‘facility’ for small molecules and biosynthetic precursors such as amino acids and polyphosphates. These precursors are essential in processes such as osmoregulation, which involves the regulation of intracellular fluids. Since yeast is a living organism, it carries out a number of life processes which allow it to survive. As all living cells including yeast, require energy for it to carry out cellular processes like cellular respiration- an essential process which enables living cells to function normally. Cellular respiration is the process of energy in the form of ATP being released from the glucose found in food.

Formula for aerobic cellular respiration

C6H12O6 (glucose) + 6O2 (oxygen)→ 6H2O (Water) + 6CO2 (Carbon dioxide) + ATP(Energy)

Formula for anaerobic cellular respiration

C6H12O6 (glucose)→ 2CH3CH2OH (Alcohol) + 2CO2 (Carbon dioxide) + ATP(Energy)

This process can be carried out both aerobically and anaerobically. We can from the formulas above that the difference between aerobic and anaerobic respiration is that the formula for aerobic respiration requires oxygen while anaerobic respiration does not. Anaerobic respiration also produces alcohol as a by-product instead of water. Bread production is a prime example of when yeast respires.

During this process, the yeast first respires anaerobically as it reacts with the oxygen and sugar in the dough excreting carbon dioxide gas and water to help the bread rise. After a period of time when the oxygen source is cut off, the yeast in the dough is forced to respire anaerobically. Similarly, this produces carbon dioxide gas as well as ethanol which evaporates when the dough is placed into an oven- a high temperature environment. A high temperature environment like the inside of an oven, also causes the rate of cellular respiration to effectively diminish as the enzymes essential in this reaction are denatured by the extreme temperatures. This is why bread in a hot oven will only rise to a certain point before coming to a halt as the process of cellular respiration involving these enzymes are denatured. In contrast, the rate of cellular respiration in yeast cells will also slow because of low temperatures, this is due to the slower vibrations and movements of molecules in lower temperatures.

The optimum temperature for yeast to respire in is in room temperature conditions, as this is considered the ‘sweet spot’ where conditions are not too hot nor too cold. After various experiments like this, humans have learned to manipulate the yeast such as placing their baking in warm in order to maximise the rate of cellular respiration which allows the bread to be made at a faster pace. The reproduction of yeast cells known as budding. The budding process involves the yeast cell splitting into two forming a smaller bud(bleb) on the outside of the parent cell. A bleb has its own nucleus and with time will detach from the parent cell and will eventually grow into a full sized yeast cell. Sufficient nutrients is key for the yeast cells to survive. As a result, without nutrients, yeast will be unable to reproduce and will gradually perish. The acidity and alkalinity the environment yeast is in will also have a great impact on the reproduction of yeast cells. Yeast, along with other fungi, are unable to adjust their internal pH levels, therefore an environment that is too acidic or basic threatens the survival of yeast cells. As a result of this, humans have learned and adapted to prevent yeast from making contact with acidic or basic ingredients to allow for reproduction in order to maximise the potential of yeast.

Lacking a distinct nucleus, the prokaryoteLactobacillusAcidophilus has an overall rod-shaped body. Just like other bacteria, a LactobacillusAcidophilus cell features flagella, a cell membrane and nuclear matter. Each of these organelles have specific jobs which contribute to maintaining the normal function of a cell. For example, the cell membrane is responsible for regulating the movement of cells and molecules in and out of the cell. Moreover, L.Acidophilus usually link up in small chains 0.5 to 0.8 micrometres in width and 2 to 9 millimetres in length. L.Acidophilusutilises a type of asexual reproduction called binary fission. This is the process where the ‘parent’ cell divides into two individual cells each having their own nucleus.

The bacteria continue to exponentially reproduce as each new cell that is formed from binary fission is able to reproduce again. In fact, in ideal conditions where warmth(30-40 degrees ideally), moisture and sufficient food are all present, bacteria cells are able to reproduce once every 20 minutes. Furthermore, in imperfect conditions where either moisture, warmth and sufficient food are not present. The rate of bacteria reproduction slows significantly due to the absence of these factors. In addition, L.Acidophilus relies on a sufficient food source in order to survive. Without proper nutrition, the survival of Acidophilus is at risk. All living organisms carry out respiration, as they require energy to survive. L.Acidophilus is able to carry out respiration both aerobically and anaerobically(with oxygen). Factors that threaten the ability for L.Acidophilus to respire, include the pH level and moisture levels. As mentioned before, bacteria do not have an internal pH regulator. As a result, bacteria are unable to survive in extremely acidic or basic environments. The optimum pH environment for bacteria to live in is a neutral pH of 7.

The moisture level around a bacteria cell- L.Acidophilus in this case, is also another crucial factor in the survival and normal function of a bacteria cell. Since bacteria is made from 80% to 90% water, water is needed for the cell to grow. If too much water/fluids were to pass through the cellular membrane of a bacteria cell- the cell would no longer be able to survive. Though Acidophilus naturally live in our gastrointestinal tract, this probiotic is also commonly found in supplements and fermented foods such as yoghurt. Health supplements containing acidophilus have also demonstrated to be beneficial to the health of an individual in a number of areas including reduction of cholesterol levels, prevention of diarrhoea and vaginal infections, as well as, restoring normal flora after the use of antibiotic therapy. An example of how humans manipulate Acidophilus in order to adjust and maximise its potential is when we adjust the variation of bacteria in yoghurt starter cultures. Starter cultures are a blend of different types of bacteria which convert the lactose in milk into lactic acid resulting in a slightly acidic tangy taste in yoghurt.

Yeast and L.Acidophilus share a number of similarities and differences. For example, L.Acidophilus produces through binary fission whereas yeast utilizes a process called budding. Despite lacking a defined nucleus, L.Acidophilus shares a very similar intracellular structure to yeast, as they both have features such a cell membrane and cytoplasm. Additionally, yeast cells have a vacuole to store fluids and nutrition, while L.Acidophilus features flagella on the outside of the cell to aid with the movement of the cell.

Furthermore, both microbes are able to carry out cellular respiration both aerobically and anaerobically, allowing them to release energy from food while producing by-products such as carbon dioxide gas and ethanol, essential in the production of bread and beer. Moreover, in optimum conditions, L.Acidophilus is able to reproduce once every 20 minutes, whereas yeast cells only reproduce once approximately every 2 hours. This means that L.Acidophilus cells are able to reproduce at a quicker rate compared to yeast cells, meaning that L.Acidophilus cells have higher chances of survival compared to yeast when faced with unfavourable conditions, as they are able to reproduce at a faster rate.

To conclude, we can see that yeast and L.Acidophilus have proven to be microbes that bring a positive impact on human life. A large factor into why we as humans have been able to benefit from these two microbes is due to our extensive biological knowledge. For instance, we understand that yeast produces carbon dioxide gas as a by-product when it respires aerobically. Because of this piece of knowledge have learned to use it in bread production to allow the dough to rise. L.Acidophilus is another example of how we have investigated its properties, and as a result, it is now commonly found in supplements providing immense health benefits to us humans.