Science: Small but perfectly informed

The latest insight into bacterial behaviour reveals an organism sensitively tuned to its environment, writes Bernard Dixon

Because they are very small, microbes are often described as simple, elementary or primitive. Most slanderously, they are "lower forms of life".

Not so. Most microbes are single cells, each capable of diverse functions for which we, like other "advanced" creatures, require specialised tissues and organs. Bacteria, for example, do not have multi-layered, multi-cellular skin, with hairs, sweat cells and freckles, as a barrier to protect them from the outside world. Instead, each individual cell is shielded from the environment by a sturdy wall, with a delicate membrane beneath.

Likewise, bacteria move around by using whip-like parts of the cell called flagellae, rather than legs and feet that require shoes and socks. They break down food materials perfectly well without the benefit of a digestive tract. And they enjoy an active sex life without weird-looking organs for that purpose.

It is precisely because microbes achieve so much with so little that scientists have long used them to study the fundamental processes of life. In recent years, researchers have increasingly recognised the paramount significance of one particular microbial skill - that of sensing chemical and physical changes outside the cell. This can be crucially important when a microbe detects a new source of food in its environment, for example, or when, suddenly deprived of water, it must form a protective spore to survive until more favourable conditions return.

The other reason why scientists are interested in microbial senses is that their mechanisms can throw light on their counterparts in human cells. Although much detail remains to be clarified, it is becoming clear that both types of cell have exquisitely sensitive processes through which they respond to changes in the environment. They do so by means of sequences of signals propagated from the cell surface to the working machinery determined by the genes in the nucleus. Several diseases are associated with failures in this system. The prime example is the loss of responsiveness that characterises cancer cells and which leads to their disorderly and damaging proliferation.

The latest insight into the way microbes recognise changes in their environment comes from research carried out at the Centre for Cellular and Molecular Biology in Hyderabad, India. MK Ray and his colleagues have been studying the capacity of bacteria growing in Antarctica to react when conditions become warmer or cooler. Their work indicates that certain proteins in the cell membrane change chemically when temperature rises or falls. This change serves as a signal which in turn triggers appropriate alterations in the cell's internal genetic machinery.

The membrane around a bacterial cell is much more than simply a bag to retain the contents. Surrounded by a cell wall that is rigid but permeable, and which prevents the delicate membrane bursting, it is an active rather than passive structure. For example, it regulates the rates at which food is imported into the cell and waste substances are excreted.

The new evidence from Hyderabad has emerged from research into a bacterium which Ray and his collaborators isolated from soil in the Antarctic, where the temperature fluctuates over a surprisingly wide range. It is a strain of Pseudomonas syringae, which thrives especially well at 22C, though it can grow (more slowly) at temperatures down to 0C and (more quickly) at temperatures up to 30C.

But how does the entire, complex process of growth (including assembly of new cellular materials and provision of requisite energy) respond to warming or cooling? The Indian researchers believe the initial signal comes from two membrane proteins, altering their chemistry with changes in temperature. Like many other proteins, they can be phosphorylated (combined with phosphate), and this alters their behaviour. In this case, one of the proteins is phosphorylated only at temperatures up to 15C, while the other is phosphorylated more at higher than lower temperatures.

We do not yet understand how such changes initiate the signals affecting the expression of genes which cause a bacterium to grow more quickly or slowly. However, these are precisely the sort of changes implicated in other types of response to the environment. From preliminary tests in other bacteria, Mr Ray and his colleagues believe a similar mechanism operates in some, but not all, other Antarctic microbes.

Forty years ago this month, the Dutchmen Jan Kluyver and CB van Niel were completing their book The Microbe's Contribution to Biology, a classical text that highlighted the enormous debt science owed to unseen micro-organisms as research tools. Even then, it was clear that bacteria and other microbes, despite their minute dimensions and apparent simplicity, had in many ways helped to lay the foundations of biochemistry and genetics. Kluyver and van Niel paid tribute accordingly. Yet even they would be astonished to learn that Pseudomonas syringae is now illuminating questions of senses, signals and responses to the environment. In 1955, such matters would not have merited a moment's discussion. Microbes simply did not have senses.

Start your day with The Independent, sign up for daily news emails
Arts and Entertainment
Joe Cocker performing on the Stravinski hall stage during the Montreux Jazz Festival, in Montreux, Switzerland in 2002
musicHe 'turned my song into an anthem', says former Beatle
News
Clarke Carlisle
sport
Sport
footballStoke City vs Chelsea match report
Arts and Entertainment
theatreThe US stars who've taken to UK panto, from Hasselhoff to Hall
PROMOTED VIDEO
ebooks
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Life and Style
Approaching sale shopping in a smart way means that you’ll get the most out of your money
life + styleSales shopping tips and tricks from the experts
News
newsIt was due to be auctioned off for charity
News
Coca-Cola has become one of the largest companies in the world to push staff towards switching off their voicemails, in a move intended to streamline operations and boost productivity
peopleCoca-Cola staff urged to switch it off to boost productivity
Environment
Sir David Attenborough
environment... as well as a plant and a spider
Voices
'That's the legal bit done. Now on to the ceremony!'
voicesThe fight for marriage equality isn't over yet, says Siobhan Fenton
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Austen Lloyd: Regulatory / Compliance / Exeter

Excellent Salary: Austen Lloyd: Exeter - An excellent opportunity for a Solici...

Ashdown Group: IT Support Technician - 12 Month Fixed Term - Shrewsbury

£17000 - £20000 per annum: Ashdown Group: IT Helpdesk Support Technician - 12 ...

The Jenrick Group: Maintenance Planner

£28000 - £32000 per annum + pension + holidays: The Jenrick Group: Maintenance...

The Jenrick Group: World Wide PLC Service Engineer

£30000 - £38000 per annum + pesion + holidays: The Jenrick Group: World Wide S...

Day In a Page

Isis in Iraq: Yazidi girls killing themselves to escape rape and imprisonment by militants

'Jilan killed herself in the bathroom. She cut her wrists and hanged herself'

Yazidi girls killing themselves to escape rape and imprisonment
Ed Balls interview: 'If I think about the deficit when I'm playing the piano, it all goes wrong'

Ed Balls interview

'If I think about the deficit when I'm playing the piano, it all goes wrong'
He's behind you, dude!

US stars in UK panto

From David Hasselhoff to Jerry Hall
Grace Dent's Christmas Quiz: What are you – a festive curmudgeon or top of the tree?

Grace Dent's Christmas Quiz

What are you – a festive curmudgeon or top of the tree?
Nasa planning to build cloud cities in airships above Venus

Nasa planning to build cloud cities in airships above Venus

Planet’s surface is inhospitable to humans but 30 miles above it is almost perfect
Surrounded by high-rise flats is a little house filled with Lebanon’s history - clocks, rifles, frogmen’s uniforms and colonial helmets

Clocks, rifles, swords, frogmen’s uniforms

Surrounded by high-rise flats is a little house filled with Lebanon’s history
Return to Gaza: Four months on, the wounds left by Israel's bombardment have not yet healed

Four months after the bombardment, Gaza’s wounds are yet to heal

Kim Sengupta is reunited with a man whose plight mirrors the suffering of the Palestinian people
Gastric surgery: Is it really the answer to the UK's obesity epidemic?

Is gastric surgery really the answer to the UK's obesity epidemic?

Critics argue that it’s crazy to operate on healthy people just to stop them eating
Homeless Veterans appeal: Christmas charity auction Part 2 - now LIVE

Homeless Veterans appeal: Christmas charity auction

Bid on original art, or trips of a lifetime to Africa or the 'Corrie' set, and help Homeless Veterans
Pantomime rings the changes to welcome autistic theatre-goers

Autism-friendly theatre

Pantomime leads the pack in quest to welcome all
The week Hollywood got scared and had to grow up a bit

The week Hollywood got scared and had to grow up a bit

Sony suffered a chorus of disapproval after it withdrew 'The Interview', but it's not too late for it to take a stand, says Joan Smith
From Widow Twankey to Mother Goose, how do the men who play panto dames get themselves ready for the performance of a lifetime?

Panto dames: before and after

From Widow Twankey to Mother Goose, how do the men who play panto dames get themselves ready for the performance of a lifetime?
Thirties murder mystery novel is surprise runaway Christmas hit

Thirties murder mystery novel is surprise runaway Christmas hit

Booksellers say readers are turning away from dark modern thrillers and back to the golden age of crime writing
Anne-Marie Huby: 'Charities deserve the best,' says founder of JustGiving

Anne-Marie Huby: 'Charities deserve the best'

Ten million of us have used the JustGiving website to donate to good causes. Its co-founder says that being dynamic is as important as being kind
The botanist who hunts for giant trees at Kew Gardens

The man who hunts giants

A Kew Gardens botanist has found 25 new large tree species - and he's sure there are more out there