Three Bacteria that Make the Nice List

Bacteria get a bad rap – especially those that live on or inside humans. Outbreaks of Salmonella spp. and Listeria monocytogenes make headlines. Fall comes and we’re told to battle bad germs with hand washing and various disinfectants. Even here we’ve highlighted dangerous antibiotic-resistant bacteria. However, most microbes that call humans home have a symbiotic relationship with us. They help the immune system, synthesize certain vitamins, and break down hard to digestion compounds. Here are three examples of super good bacteria that we are grateful for and adding to our holiday wish list!

Lactobacillus acidophilus is a gram-positive, immobile, and rod-shaped bacteria that’s become the poster child for probiotics (good bacteria). That’s because these little microbes can help alleviate diarrhea and constipation, fight cavities, reduce heartburn, enhance immunity, and even lower cholesterol. How do they accomplish all this? Mainly by moving into our gastrointestinal (GI) tract and then keeping other pathogenic bacteria out! A robust population of L. acidophilus in a person’s GI tract helps the body maintain a healthy mucus surface along the track and produces highly effective antimicrobial proteins that target pathogenic bacteria. As a cherry on top you can also thank this species every time you successfully eat ice cream. That’s because L. acidophilus produces the enzyme lactase which is essential for breaking down lactose. L. acidophilus populations are prolific in most healthy individuals but can get wiped out by certain antibiotics. Luckily these populations are easy to reestablish either by taking supplements or eating most yogurts.

L. acidophilus Mogana Das Murtey and Patchamuthu Ramasamy, CC BY-SA 3.0

Bifidobacterium adolescentis are also gram-positive, immobile bacteria that have a distinct bifid (y-shaped) form. These little microbes are with us from the start – studies have shown that they begin colonizing our intestines immediately after birth. And that’s a good thing! In infants, B. adolescentis removes the protein casein which helps with milk digestion, produces essential B vitamins, releases acids that help prevent constipation, and out-compete pathogenic bacteria. This beneficial relationship continues for a lifetime although poor diet, stress, and repeated antibiotic use can cause a decline in B. adolescentis as humans age. That’s unfortunate as this bacteria species helps to lower cholesterol in adults, may prevent colon cancer, and more generally aids in the body’s antitumor defenses.     

B. adolescentis Y tambe, CC BY-SA 3.0

Streptococcus thermophilus are gram-positive, round, and heat-loving bacteria. They tend to gather in chains and resemble a string of beads – hence the genus name Streptococcus meaning twisted kernel. Unlike its relative Streptococcus pyogenes which can cause strep throat, S. thermophilus is a force for good especially when it comes to our digestion. While many bacteria help us digest carbohydrates and sugars only a handful help with proteins and lipids. S. thermophilus is one of them! Like other probiotics, S. thermophilus also produces situation-specific antibiotic chemicals that protect us from more dangerous bacteria without hurting neighboring beneficial bacteria. Researchers have also noticed a correlation between S. thermophilus populations and a WIDE range of health benefits including reduced childhood colic, increased antitumor activity, reduced AIDS symptoms, reduced IBS symptoms, reduced atopic dermatitis, and lower rates of respiratory infections. Last but not least, S. thermophilus is also used to make several types of cheese including swiss and mozzarella!

S. thermophilus Adam Benyoussef, CC BY-SA 3.0

Ready to include these hospitable microbes in your holiday fun? Try adding kimchi to the appetizer table, making buttermilk pancakes for a festive breakfast, or use whole milk yogurt in a pie toppings. Ready to learn more about bacteria? Check out our experiments (Identification of Bacteria, Battling Bacteria: Ecosystem Dynamics in a Petri Dish, Bioremediation by Oil Eating Bacteria) or our fun Bacteria rings activity!   

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