The strange sci­ence of breast milk may change the way you think about bac­te­ria.

North & South - - Contents - nerd na­tion by jenny nicholls

Jenny Nicholls on the 39 tril­lion, mostly won­drous, mi­cro­bial cells liv­ing in and on us.

It was ei­ther the club sand­wiches (of­fice shout), or the take­away chicken foo yung I ate later. By the next day, I was vom­it­ing, twice an hour, ev­ery hour.

After 48 hours of non­stop clench­ing, my stom­ach felt like an or­ange on a mo­tor­way, and I was barf­ing (sen­si­tive read­ers, turn away) blood. So I caught a cab to the doc­tor’s, a bowl on my knees. Even though the trip lasted only a few min­utes, I didn’t make it out of the cab with­out vom­it­ing. At the doc’s, I was ush­ered into a side room where I could throw up in pri­vate.

My boyfriend, a med stu­dent, glee­fully di­ag­nosed sal­mo­nella poi­son­ing, and pre­scribed gal­lons of wa­ter to keep me hy­drated. My GP, who gave me an anti- emetic shot, agreed. Although I was bet­ter in a few days, my stom­ach felt raw for weeks.

Although this brush with “path­o­genic” (dis­ease-caus­ing) bac­te­ria was decades ago, I re­mem­ber it vividly. The res­i­dents of Have­lock North, I have no doubt, will re­call the fright­en­ing campy­lobac­ter bac­te­ria con­tam­i­na­tion of their pub­lic wa­ter sup­ply for the rest of their lives.

For such tiny an­i­mals, bac­te­ria cast a long shadow. Yersinia pestis, the plague bac­terium (aka the Black Death) mowed down so many it changed the course of his­tory – and My­cobac­terium tu­ber­cu­losi (aka “con­sump­tion”) killed even more, chok­ing to death the Bron­tës, Chekhov, Kafka, Keats, D.H. Lawrence, Kather­ine Mans­field, Molière, Ge­orge Or­well and Chopin, among mil­lions of oth­ers.

The “lin­ger­ing cul­tural scar” of these bugs, as award-win­ning sci­ence writer Ed Yong puts it in his as­tound­ing new book I Con­tain Mul­ti­tudes (Bod­ley Head, $55), casts bac­te­ria as feared con­tam­i­nants. Germs are not only bad, they are dis­gust­ing. Ex­ter­mi­nate!

But this widely held view is not only wrong, it is wrong on an epic scale, ex­plains Yong (in­ter­viewed, over­leaf ). Most mi­crobes are not pathogens. Fewer than 100 species of bac­te­ria cause ill­ness in hu­mans.

It is hard to get your head around,

but the 30 tril­lion cells in your body are ac­com­pa­nied by an es­ti­mated 39 tril­lion mi­cro­bial ones. This is your mi­cro­biome and it be­haves, Yong ex­plains, like an or­gan, “as im­por­tant as a stom­ach or an eye”.

So, what is your mi­cro­biome made up of? Bac­te­ria, mostly – but there are also fungi, mys­te­ri­ous or­gan­isms called ar­chaea, and vast num­bers of viruses, mostly in­fect­ing the bac­te­ria. It’s a jun­gle in there – and also a desert and a for­est and a city. Our body, in­side and out, con­tains a range of en­vi­ron­ments, each home to its own fauna.

“Each of us has our own dis­tinc­tive mi­cro­biome,” writes Yong, “sculpted by the genes we in­her­ited, the places we’ve lived in, the drugs we’ve taken, the food we’ve eaten, the years we’ve lived, the hands we’ve shaken.”

Your cells carry around 20,000 genes, but the mi­crobes in­side you con­tain 500 times more – func­tion­ing, in other words, like tiny, in­de­pen­dent chem­i­cal fac­to­ries. “This ge­netic wealth, com­bined with their rapid evo­lu­tion, makes them masters of bio­chem­istry, able to adapt to any pos­si­ble chal­lenge. They help to digest our food, re­leas­ing oth­er­wise in­ac­ces­si­ble nu­tri­ents. They pro­duce vi­ta­mins and min­er­als that are miss­ing from our diet. They break down tox­ins and haz­ardous chem­i­cals. They (even) pro­tect us from dis­ease.”

It now seems our body wouldn’t de­velop prop­erly with­out a bal­ance of mi­crobes, and a long list of com­plaints have been linked to dis­rup­tions in the bio­di­ver­sity of our germs. A dis­ease like cholera, for ex­am­ple, could be likened to an en­vi­ron­men­tal dis­as­ter, such as the one in Guam, where in­tro­duced tree snakes have swal­lowed whole species of native birds.

One day, we might well be able to tweak our mi­cro­biomes to fix dis­eases as di­verse as al­ler­gies, di­a­betes, de­pres­sion and heart dis­ease. And not just ours. Yong also ex­plores the idea of a build­ing’s mi­cro­biome – like that of a hos­pi­tal, where fresh air can bring in harm­less out­door mi­crobes and whisk away pathogens emit­ted by pa­tients.

Emit­ted? “All of us are con­stantly seed­ing the world with our mi­crobes,” he writes. “Ev­ery time we walk, talk, scratch, shuf­fle or sneeze, we cast a per­son­alised cloud of mi­crobes into space. Ev­ery per­son aerosolises around 37 mil­lion bac­te­ria per hour.”

So Florence Nightin­gale was ahead of her time when she put pa­tients next to open win­dows. Yong quotes a re­searcher who found hos­pi­tal air, to her shock, to be a bouil­l­abaisse of pathogens rare or ab­sent in the air just out­side.

Although he doesn’t over-hype the sci­ence, Yong con­veys the ex­cite­ment of evolving dis­cov­er­ies in a field that’s hot­ter than hot. (Bugs. Fash­ion­able. Yep.)

An­other spec­tac­u­lar find­ing in­volves hu­man breast milk, now known to con­tain a ridicu­lously long list of com­plex sug­ars; more than 200 dif­fer­ent kinds. This is odd, be­cause hu­man ba­bies can­not digest them.

But some­thing else can. It seems they don’t feed the baby at all – but the baby’s bac­te­ria. Eek!

Bi­fi­dobac­terium in­fan­tis, in par­tic­u­lar, thrives on this diet, which makes it the dom­i­nant bac­te­ria in the guts of breast­fed ba­bies. And the bug is a stel­lar ten­ant, help­ing to “cal­i­brate” the baby’s im­mune sys­tem – which is, by the way, not so much “im­ma­ture” as di­alled back, to al­low an in­flux of bac­te­ria it needs.

“The ob­vi­ous mes­sage is that breast milk is good,” said Yong in an in­ter­view with Vox mag­a­zine. “But if you’re not breast­feed­ing, you’re not screw­ing up your baby’s mi­cro­biome. One of the things I no­ticed when I was re­search­ing the book is that these path­ways are very re­silient. The devel­op­ment of the mi­cro­biome can go down lots of dif­fer­ent paths.”

Breast milk is just one ex­am­ple of the mind-bog­gling sym­bio­sis be­tween bac­te­ria and their hosts, the true ex­tent of which we are only just be­gin­ning to un­der­stand. +

“Ev­ery time we walk, talk, scratch, shuf­fle or sneeze, we cast a per­son­alised cloud of mi­crobes into space.”

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