COLUMN: Bacteria can be both friend and foe

UVic biologist gives the lowdown on good and bad bacteria

Bacteria are everywhere. A few give diseases like tuberculosis (Mycobacterium tuberculosis), but most are very useful. Some lactic acid bacteria transform milk into yogurt; others make cheddar cheese from milk.

One gram of yogurt, for example, has as much as 10 million Lactobacillus delbrueckii bulgaricus bacteria and 100 million Streptococcus thermophilus, which represent for a 100g cup of yogurt a total of 11 billion lactic acid bacteria. These bacterial cultures can also be purchased in small packets in the grocery store to make yogurt at home. Those I bought here in Victoria looked like a white powder that can be added to milk after it has been heated and slowly cooled.

Leaving the inoculated milk in a warm place (I personally use the oven) for few hours allows these lactic acid bacteria to grow by feeding on lactose and casein in the milk, and to produce lactic acid, giving the yogurt its slightly sour taste. Other lactic acid bacteria like Lactobacillus plantarum, for instance, play a key role in the fermentation of vegetables like cabbage (sauerkraut) or green Manzanillo olives that are found in grocery stores.

Although these bacteria are very small, they still can contract a cold-like virus. When you catch a cold, you have been infected with a type of virus scientists call Rhinovirus.

Compared to bacteria, the vast majority of viruses are about 10 times smaller. But unlike bacteria, they cannot divide on their own. They have to be inside a cell to be able to replicate their genes and produce their proteins.

Viruses can also infect the lactic acid bacteria that are so important in the dairy industry. Because the bacterium infected with a virus disappears, these viruses became known as bacteriophages (eater of bacteria), or more simply “phages.” More accurately, phages break up the cells in a process called cell lysis, which releases several copies of the phage that initially infected the bacterium.

There are many types of phages, but they are usually specific to only one type of bacteria. If one type of phage starts infecting the lactic acid bacteria used in a yogurt or cheese factory, it can be catastrophic. It is like an infection in a hospital. It slows down the production of cheese and causes economic losses until the phages are removed.

Phages sometimes may even be the cause of tragic outcome. When a phage called beta phage infects a bacterium called Corynebacterium diphtheria, it produces a very potent toxin and a disease (diphtheria) that can kill people. Today, the diphteria-tetanus-pertussis (DTaP) vaccine contains an inactive toxin, which allows vaccinated children to build immunity against the diphtheria toxin. Before law required pasteurization of milk, raw milk was one of the ways diphtheria was transmitted.

The first to discover phages was a Canadian born in Montreal: Félix d’Hérelle (1873-1949). He found a phage of dysenteric bacteria that could clear a cloudy culture without the phage being retained by a porcelain filter. In time, other phages were discovered and became models in the study of the molecular basis of life.

Today we know that phages may play an important role as a genetic shuttle between different types of bacteria, which is one mechanism that explains the development of resistance of bacteria to antibiotics.

Between 1896 and 1899, before his discovery of bacteriophage, d’Hérelle received a grant from the Canadian Minister of Revenue to develop a method of fermentation of maple syrup for the production of whisky. The minister was Henri-Gustave Joly de Lotbinière (1829-1908), the seventh governor of British Columbia from 1900 to 1906.

Réal Roy is a microbiologist and an assistant professor in the department of biology at the University of Victoria.

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Greater Victoria man killed in Alberta accident was expectant father

Geordie Murray described as ‘wonderful husband, brother son and friend’

VicPD says circumstances around missing teen are ‘high-risk’

Arianna McKenzie last seen in Centennial Square

Canada Post aware of ongoing email, text phishing scams

Scammers pretending to be Canada Post will ask for personal and payment information

Suicide rates not impacted by seasons

While men are three times more likely to commit suicide, women have higher rates of depression

VIDEO: Music stars pay tribute to Kobe Bryant at Grammys award show

Music artists including Billy Ray Cyrus, Rick Ross and Kirk Franklin paid tribute to Bryant

Pregnant B.C. woman stuck in Wuhan, the epicentre of coronavirus outbreak

Woman is due to give birth in Wuhan, China unless she can get out

Ontario confirms second presumptive coronavirus case in wife of first patient

Both arrived on a China Southern Airlines flight after having been to Wuhan

Canada’s basketball community mourns Kobe Bryant after helicopter crash

Bryant was an 18-time NBA all-star who won five championships

‘Devastated’: Fans, celebrities remember Kobe Bryant after his death

Bryant played all of his 20-year career with the NBA with the Los Angeles Lakers

Investigation launched after six dead puppies dumped in Richmond hotel parking lot

RAPS reminds people they can always give up puppies they can’t take care of

Canadian Lunar New Year celebrations dampened by coronavirus worries

But Health Minister Patty Hajdu said today that the risk of infection is low

B.C. VIEWS: New coronavirus outbreak an important reminder

Walking the line between cautious and alarmist

Kobe Bryant, daughter killed in California helicopter crash

Bryant entered the NBA draft straight out of high school in 1996

Most Read