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How Bacteria Invade: New study sheds light on age-old mystery

August 25, 2016

Toron­to, ON –  They’re small, unas­sum­ing – and poten­tial­ly dead­ly. And while most bac­te­ria are ren­dered harm­less by the body’s defense mech­a­nisms, to date there has been very lit­tle under­stand­ing of exact­ly how bac­te­ria are able to nav­i­gate the blood stream to invade organs, where they can cause mas­sive dam­age and in some cas­es, death. But in a study pub­lished in the jour­nal Cell Reports this week, sci­en­tists at the Uni­ver­si­ty of Toron­to have used a new live-imag­ing sys­tem to shed new light on this ancient mys­tery. To their sur­prise, the researchers found that bac­te­ria uti­lize the same strate­gies for inva­sion as the body’s immune cells use for defense.

The team focused their study on the bac­teri­um B. burgdor­feri, known to cause Lyme dis­ease which can invade joints, brain, heart and oth­er tis­sues. This bac­te­ria is part of the spiro­chete fam­i­ly of bac­te­ria asso­ci­at­ed with dis­eases such as relaps­ing fever, lep­tospiro­sis, and peri­odon­tal dis­ease, and are a major cause of human dis­ease world­wide.

To uncov­er the secrets behind this bacteria’s mas­sive suc­cess, the team devel­oped nov­el imag­ing analy­sis meth­ods to cap­ture and study thou­sands of films of the indi­vid­ual bac­teri­um in flow cham­bers and blood ves­sels.

“It’s always been hard to under­stand why spiro­chete bac­te­ria are so high­ly inva­sive,” explained Tara Mori­ar­ty, Assis­tant Pro­fes­sor at the Fac­ul­ty of Den­tistry and the Depart­ment of Lab­o­ra­to­ry Med­i­cine and Patho­bi­ol­o­gy, Temer­ty Temer­ty Fac­ul­ty of Med­i­cine, and senior author of the study.

That’s because once bac­te­ria enter the blood­stream – say, from the bite of a tick – they face a great deal of force. Imag­ine a fast-flow­ing riv­er: the blood­stream should exert enough force to sweep the bac­te­ria through the cir­cu­la­to­ry sys­tem and into the liv­er, spleen and lungs, where they would be met by the body’s immune sys­tem and elim­i­nat­ed.

But in fact, the bacteria’s catch bonds grow stronger as they encounter more force from blood flow, which makes them par­tic­u­lar­ly good at stick­ing to blood ves­sels.

Liken­ing their imag­ing process to “pluck­ing a sin­gle cell out of a haystack,” and filmed in real time, the researchers deduced that indi­vid­ual bac­teri­um use ‘catch bonds’ and ‘teth­ers’, some­thing like an anchor on a rope, to hook onto the blood vessel’s endothe­lial cells and slow down. The pro­peller-like struc­tures which help bac­te­ria pro­pel for­ward appear to allow the bac­te­ria active con­trol of their move­ments, enabling them to wrig­gle out of the flow­ing riv­er of blood and make their way into oth­er parts of the body.

“This is the first time we’ve seen this with any bac­teri­um,” said Mori­ar­ty

But per­haps the most strik­ing fea­ture of the bacteria’s inva­sion tac­tics is that they are eeri­ly sim­i­lar to those of the body’s own immune cells. Dif­fer­ent in terms of their shape, size and sur­face pro­teins, bac­te­ria and white blood cells nonethe­less seem to move about the body using the same catch-teth­er tech­niques. “It’s pret­ty sur­pris­ing and fas­ci­nat­ing that you’d see bac­te­ria [use these meth­ods], too,” Mori­ar­ty added.

The study’s first author, Fac­ul­ty of Den­tistry PhD stu­dent Rhod­a­ba Ebady, hopes that the study’s nov­el imag­ing tech­nique can be used in oth­er in vit­ro stud­ies. “I’m still pret­ty amazed at the behav­iour of the bac­te­ria when they are inter­act­ing with the endothe­lial cells. They do some very inter­est­ing things some­times,” Ebady said.

“I hope to see this research con­tin­ue for oth­er bac­te­ria that require vas­cu­lar dis­sem­i­na­tion to cause infec­tion [and that] it will lead to find­ing ways to pre­vent the dis­sem­i­na­tion of bac­te­ria,” she added.

About the Fac­ul­ty of Den­tistry, Uni­ver­si­ty of Toron­to         

Com­bin­ing the rigours of bio­log­i­cal and clin­i­cal research with a supe­ri­or edu­ca­tion­al expe­ri­ence across a full range of under­grad­u­ate and grad­u­ate pro­grams – with and with­out advanced spe­cial­ty train­ing – the Fac­ul­ty of Den­tistry at the Uni­ver­si­ty of Toron­to has earned an inter­na­tion­al rep­u­ta­tion as a pre­mier den­tal research and train­ing facil­i­ty in Cana­da. From the cut­ting-edge sci­ence of bio­ma­te­ri­als and micro­bi­ol­o­gy, to next-gen­er­a­tion nanopar­ti­cle and stem cell ther­a­pies, to ground-break­ing pop­u­la­tion and access-to-care stud­ies, the mis­sion of the Fac­ul­ty of Den­tistry is to shape the future of den­tistry and pro­mote opti­mal health by striv­ing for integri­ty and excel­lence in all aspects of research, edu­ca­tion and clin­i­cal prac­tice.

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Media Con­tact:

Erin Vol­lick
Com­mu­ni­ca­tions Offi­cer, Fac­ul­ty of Den­tistry
Tel: 416–979-4900 ext. 4381