Microbe(s) of the Month — February 2017 — Lactic Acid Bacteria!

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Not Lactic Acid Bacteria

Greetings from all of us at Microbe of the Month HQ in sunny Peoria, Indiana! Our dedicated staff of low paid wage slaves and assorted hangers-ons have finally returned from their annual 3 month vacations, are fully rested, and each is ready to dive headlong into another amazing year of edutational infotainment chock full of all the crazy facts, half-truths, and sciency thing-a-ma-bobs you have come to expect from Microbe of the Month. Ii is with great pleasure that I introduce this month’s nominee(s), the lactic acid bacteria (LABs).

It’s no secret that we like to have a good time here at microbe of the month. In fact our annual Christmas party is hands-down the most happening holiday time event in Peoria every year. When it comes to good times nothing delivers the goods like getting drunk. Our staff feature a bevy of experts in the field, many of whom have only one or two drunken disorderly charges on their records. There is a tradition of hard drinking here that can be traced all the way back to our founder, the legendary Howard Ven Trusseldorf III. It was said he drank from sunup to sundown 7 days a week. Even though his crippling alcoholism eventually pickled his liver and he died of cirrhosis at the tragically young age of 43 he still managed to transform microbe of the month from a “crazy idea” to a full-fledged Fortune 20,0000 company in only ten short years.

What does any of this have to do with microbiology or lactic acid bacteria you may be asking yourself. Well you see Mr. Trusseldorf’s alcoholic beverage of choice was wine. I much prefer a quicker route to drunk city and favor everclear myself, but wine is quite popular with lots of people I have been told. When most people think of microorganisms and alcohol, yeast immediately comes to mind. It is the yeasts after all that are responsible for the production of the alcohol itself via the process of fermentation. Basically they eat sugar and excrete alcohol. Same things happens to me the next day after a typical night out. It turns out that other microorganisms play an important role as well, specifically in the production of wines, via a process called malolactic fermentation. Malolactic bacteria, which are subset of lactic acid bacteria, are able to convert the malic acid found in most grapes into lactic acid. This has profound effects on the total acidity (TA and/or pH) of the wine, but more importantly on its flavor profile. Wine snobs refer to the flavor changes as “reduction in sharpness of the acid” and “imparting of a buttery quality” among a slew of other flavor benefits. Malolactic bacteria occur naturally on grapes however in modern winemaking these natural flora are typically killed off and a particular strain (most often Leuconostoc oenos) is added back in during the primary fermentation. The timing of the addition is tricky because MLBs are sensitive to high alcohol concentrations and will be killed if added to late in the process.

Beyond winemaking Lactic acid bacteria are among the most important groups of microorganisms used in food fermentations. They contribute to the taste and texture of fermented products and inhibit food spoilage bacteria by producing growth-inhibiting substances and large amounts of lactic acid. As agents of fermentation LAB are involved in making yogurt, cheese, cultured butter, sour cream, sausage, cucumber pickles, olives and sauerkraut, but some species may spoil beer, wine and processed meats. Note to all my Eurofins readers. This last part is mostly why we test for them. People do not like spoilage.

Although many genera of bacteria produce lactic acid as a primary or secondary end-product of fermentation, the term Lactic Acid Bacteria is conventionally reserved for genera in the order Lactobacillales, which includes Lactobacillus, Leuconostoc, Pediococcus, Lactococcus and Streptococcus, in addition to Carnobacterium, Enterococcus, Oenococcus, Tetragenococcus, Vagococcus, and Weisella.

Because they obtain energy only from the metabolism of sugars, lactic acid bacteria are restricted to environments in which sugars are present. They have limited biosynthetic ability, having evolved in environments that are rich in amino acids, vitamins, purines and pyrimidines, so they must be cultivated in complex media that fulfill all their nutritional requirements. Most are free-living or live in beneficial or harmless associations with animals, although some are opportunistic pathogens. They are found in milk and milk products and in decaying plant materials. They are normal flora of humans in the oral cavity, the intestinal tract and the vagina, where they play a beneficial role. Because they are so beneficial they are often the only or the major component of many probiotic formulations marketed as cure-alls for any number of common ailments.

A few LAB are pathogenic for animals, most notably some members of the genus Streptococcus. In humans, Streptococcus pyogenes is a major cause of disease (strep throat, pneumonia, and other pyogenic infections, scarlet fever and other toxemias).

The next time you raise a glass of wine for a toast with friends and family, or even if you prefer to drink alone like me, be sure to give a thought to our (mostly) good friends the LABs. They will be forever grateful I am sure.

Kind regards and see you next month,

Microbe of the Month President and CEO

Daniel DeMarco, Ph.D.

p.s. — due to an unforeseen scheduling conflict the contest and prize committee was unable to convene this month. The committee chairman could not attend the regularly scheduled Friday meeting as he “doesn’t work on Fridays in any of the winter months, or June-Aug”. I have apologized and rescheduled for every other Tuesday at 2pm. Since the committee did not meet there will be no prize or contest this month. Do not shed a tear loyal readers. I have challenged the eggheads in R&D to come up with an amazing contest and asked accounting to cut me a big fat check. Stay tuned!

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