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Our Little Friend of the Week: Lactic Acid Bacteria

This is my first post in my ‘Our Little Friend of the Week’ series. I am a Microbiology minor (though I have taken enough classes for it to be a major by now) and have a passion for all things microbe. Actually I like microbes, parasites and viruses. I love all of it. Call it odd, but they’re fascinating. I even have microbe plushies…don’t judge me! Anyway, I know that most people who don’t study biology don’t always necessarily realize how prevalent microbes (and the like) can be in our everyday lives. So, I am doing this for a few reasons: a) it would be fun to blog about something I’m passionate about b) I can blog about this…and make it easier to understand than reading some textbook that ASSUMES you know what it’s talking about and c) It would be something different, I think. I will try to select organisms that I think are most relevant to everyday people. I will try to keep them to medically or industrially important organisms. However, there are some that aren’t necessarily important on either level but…are ones that In find to be really cool, so I will post those as well. I will ALSO not be posting any gruesome pictures…unless requested to do so 😛 I am not phased by gross pictures of people affected by the many horrible diseases cause by various microorganisms…but I know there are many who can’t stand that. So. Don’t worry about seeing anything extreme. I WILL post some photos, but only of the less horrific instances. So, here we go 🙂

For my first post of the series, I had a hard time trying to think of where to start. So, I just went with what I think is one of the more industrially important microbes I can think of right now: Lactic Acid Bacteria. There are a lot of bacteria that are involved in the food industry. Most of us don’t take the time to think of what is in our food or what is giving it taste. I consume a lot of products fermented by lactic acid bacteria, thus why I am starting here. Lactic acid bacteria have been used to ferment or culture foods for thousands of years. Lactic acid bacteria refers to a large group of beneficial bacteria that have similar properties and all produce lactic acid as an end product of the fermentation process. They are widespread in nature and are also found in our digestive systems. So, they are friendly! If you like dairy that is…and aren’t lactose intolerant. Even if you ARE…you don’t have to hate them. Although they are best known for their role in the preparation of fermented dairy products, they are also used for the fermentation of sour dough bread, sorghum beer, cassava (to produce gari and fufu), most “pickled” (fermented) vegetables, as well as sausages. I think you will find something in this list that you like eating. You can thank Lactic Acid bacteria for that!

Bifidobacterium plushy. Sorry, they don’t really look this cute.

Bacteria from the genera Lactobacillus, Leuconostoc, Pediococcus and Streptococcus are the main species involved in fermentation of the food mentioned. However, there are many others also involved. I won’t go into those though, way too much information for one day I’d think. We’ll keep it simple. Lactic acid bacteria carry out their reactions – the conversion of carbohydrate to lactic acid – without the need for oxygen. They are described as microaerophilic as they do not utilize oxygen. Because of this, they do not cause drastic changes in the composition of the food. I think the best way to get a good general idea of what bacteria does what, I’ll list a few foods/drinks and which bacteria are involved in the fermentation.


Milk is sterile at secretion in the udder but is contaminated by bacteria even before it leaves the udder of the cow. Lactic acid bacteria are usually present in the milk, and are also used as starter cultures in the production of cultured dairy products such as yogurt or sour cream. Let’s say we were making sour cream. To manufacture sour cream, the species of bacteria Streptococcus is added directly to the cream. These bacteria grow in the cream incubated at about 70 degrees producing lactic acid. The acid causes the cream to thicken and cause the flavor of sour cream we are familiar with. Overall, careful selection of the right bacterial type to be added in different foods has lead to a variety of cultured foods. Another example: most of our cheeses owe their unique flavors and textures to bacterial growth. Also, San Francisco sourdough bread would not be ‘sour’ (have acid taste) if not for lactic acid from Streptococcus sanfranciscus (no, I’m not making this up) in the dough during the time the yeast is growing and making the dough rise. The list goes on, but these are just a few examples.


Lactobacillus acidophilus: used in yogurt, buttermilk and certain cheeses.


Probiotics: Probiotics are defined as “live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host.” Yes, they are actually alive, and most of these microorganisms are bacteria. Most people think of antibiotics and antibacterial products when you mention bacteria. Both of those kill bacteria so why would you want to consume anything that has live bacteria in it? It’s all about balance. Our digestive system normally has what we would call “good” bacteria and “bad” bacteria. Maintaining the correct balance between the “good” bacteria and the “bad” bacteria is necessary for optimal health. When you consume probiotics, you are consuming “good” bacteria to help regulate and balance your digestive system. You are probably familiar with products like Activia, that do this for their products. Lactic acid bacteria such as Streptococcus Themophilus or Bifidobacterium are usually the ones behind the scenes in Probiotics.

Streptococcus Thermophilus: used in probiotic products

Bifidobacterium breve: used in probiotics.

Meat Products: The fermentation step in sausage production involves the action of a lactic acid bacterium on the sugar added to ground meat. This organism, generally a strain of Pediococcus cerevisiae added as a starter culture, ferments the sugar to lactic acid. The acid causes the meat to develop the characteristic texture associated with sausage. The flavor of sausage is due to the lactic acid, other byproducts of bacterial fermentation, salt, seasonings and nitrite. Salting also affords protection against many spoilage organisms. Nobody wants spoiled sausages.


Sauerkraut: Possibly to go on top of whatever sausage of your choice…. is fermented by various lactic acid bacteria, including Leuconostoc, Lactobacillus, and Pediococcus. It has a distinctive sour flavor, both of which result from the lactic acid that forms when the bacteria ferment the sugars in the cabbage.

Leuconostoc mesenteroides: involved in the fermentation of Sauerkraut

I think this is a good place to stop. I really hope that those that read at least walked away with a better understanding (and appreciation) for these lovely bacteria that make some of our favorite foods so flavorful and even help us with our health. Next week, I think I will start taking a look at bacteria that are involved with the production of some of my favorite things: bread…and beer! (and more). We will be looking at the lovely microorganism, Yeast! 🙂


If you have any suggestions to make these posts more to what YOU want (I’m not writing this for my own education :P), please let me know in the comments. Also, if there is something you particularly want me to write about (a disease, microbe of any kind, scientific procedure, biological phenomena…anything) let me know too!

~Bacteria are your friends~