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.

News
people Biographer says cinema’s enduring sex symbol led a secret troubled life
News
newsGlobal index has ranked the quality of life for OAPs - but the UK didn't even make it into the top 10
News
people

Kirstie Allsopp has waded into the female fertility debate again

News
In 2006, Pluto was reclassified as a 'dwarf planet'
scienceBut will it be reinstated?
PROMOTED VIDEO
News
people
News
Researchers say a diet of fatty foods could impede smell abilities
scienceMeasuring the sense may predict a person's lifespan
Sport
footballArsenal 4 Galatasaray 1: Wenger celebrates 18th anniversary in style
News
peopleStella McCartney apologises over controversial Instagram picture
News
Gillian Anderson was paid less than her male co-star David Duchovny for three years while she was in the The X-Files until she protested and was given the same salary
people

Gillian Anderson lays into gender disparity in Hollywood

Life and Style
Laid bare: the Good2Go app ensures people have a chance to make their intentions clear about having sex
techCould Good2Go end disputes about sexual consent - without being a passion-killer?
News
ebooksAn unforgettable anthology of contemporary reportage
Arts and Entertainment
Richard Burr remains the baker to beat on the Great British Bake Off
tvRichard remains the baker to beat as Chetna begins to flake
Life and Style
fashionThe Secret Angels all take home huge sums - but who earns the most?
News
i100
Arts and Entertainment
Amazon has added a cautionary warning to Tom and Jerry cartoons on its streaming service
tv
News
The village was originally named Llansanffraid-ym-Mechain after the Celtic female Saint Brigit, but the name was changed 150 years ago to Llansantffraid – a decision which suggests the incorrect gender of the saint
newsA Welsh town has changed its name - and a prize if you can notice how
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

DT Teacher - Resistant Materials

£33000 - £34000 per annum: Randstad Education Group: Technology Teacher (Resis...

Trainee Recruitment Consultant

£20000 - £25000 per annum + Uncapped Commission, 1st yr OTE £30-£40k : SThree:...

Middleware Support Analyst

£45000 - £50000 Per Annum: Clearwater People Solutions Ltd: Our client is curr...

Senior Java Developer/Designer

£400 - £450 Per Day: Clearwater People Solutions Ltd: My client are looking fo...

Day In a Page

Italian couples fake UK divorce scam on an ‘industrial scale’

Welcome to Maidenhead, the divorce capital of... Italy

A look at the the legal tourists who exploited our liberal dissolution rules
Tom and Jerry cartoons now carry a 'racial prejudice' warning on Amazon

Tom and Jerry cartoons now carry a 'racial prejudice' warning on Amazon

The vintage series has often been criticised for racial stereotyping
An app for the amorous: Could Good2Go end disputes about sexual consent - without being a passion-killer?

An app for the amorous

Could Good2Go end disputes about sexual consent - without being a passion-killer?
Llansanffraid is now Llansantffraid. Welsh town changes its name, but can you spot the difference?

Llansanffraid is now Llansantffraid

Welsh town changes its name, but can you spot the difference?
Charlotte Riley: At the peak of her powers

Charlotte Riley: At the peak of her powers

After a few early missteps with Chekhov, her acting career has taken her to Hollywood. Next up is a role in the BBC’s gangster drama ‘Peaky Blinders’
She's having a laugh: Britain's female comedians have never had it so good

She's having a laugh

Britain's female comedians have never had it so good, says stand-up Natalie Haynes
Sistine Chapel to ‘sing’ with new LED lights designed to bring Michelangelo’s masterpiece out of the shadows

Let there be light

Sistine Chapel to ‘sing’ with new LEDs designed to bring Michelangelo’s masterpiece out of the shadows
Great British Bake Off, semi-final, review: Richard remains the baker to beat

Tensions rise in Bake Off's pastry week

Richard remains the baker to beat as Chetna begins to flake
Paris Fashion Week, spring/summer 2015: Time travel fashion at Louis Vuitton in Paris

A look to the future

It's time travel fashion at Louis Vuitton in Paris
The 10 best bedspreads

The 10 best bedspreads

Before you up the tog count on your duvet, add an extra layer and a room-changing piece to your bed this autumn
Arsenal vs Galatasaray: Five things we learnt from the Emirates

Arsenal vs Galatasaray

Five things we learnt from the Gunners' Champions League victory at the Emirates
Stuart Lancaster’s long-term deal makes sense – a rarity for a decision taken by the RFU

Lancaster’s long-term deal makes sense – a rarity for a decision taken by the RFU

This deal gives England a head-start to prepare for 2019 World Cup, says Chris Hewett
Ebola outbreak: The children orphaned by the virus – then rejected by surviving relatives over fear of infection

The children orphaned by Ebola...

... then rejected by surviving relatives over fear of infection
Pride: Are censors pandering to homophobia?

Are censors pandering to homophobia?

US film censors have ruled 'Pride' unfit for under-16s, though it contains no sex or violence
The magic of roundabouts

Lords of the rings

Just who are the Roundabout Appreciation Society?