Science: Bacteria with a taste for the dirty work - A magnetic microbe offers hope of a breakthrough in detoxifying industrial waste, says Martyn Kelly

Making industrial waste clean enough to pump into a river is an expensive business as environmental regulations become stricter. In the past few years, businessmen and scientists have concentrated on biotechnology - the use of living organisms - to do this. To a layman this appears somewhat paradoxical: how can living organisms detoxify waste without themselves succumbing? That, however, underestimates that most versatile of organisms, the bacterium.

There is almost no place on earth where bacteria are not found. Several bacteria, for example, are naturally tolerant of heavy metals; others can be bred for resistance in the laboratory. Place these in an industrial effluent and toxic chemicals in it will be accumulated by the bacteria to such an extent that the effluent becomes clean enough to be discharged. That, at least, is the theory. The problem lies in moving from laboratory fermentors to factory-

sized installations. Having allowed your bacteria to accumulate metals, how do you then remove them en masse from the solution?

Three biotechnologists - Professor Derek Ellwood, of the Westlake Industrial Park in Cumbria; Professor Jim Watson, of Southampton University; and Mike Hill, of European Cancer Prevention - have hit upon a novel technique: make the bacteria magnetic. Then if the treated effluent is exposed to a magnetic field, the bacteria and toxins can be collected on to a solid surface.

'The bacteria can accumulate some metals to up to 30 per cent of their body weight,' Professor Ellwood says. 'This is a lot more concentrated than many natural metal ores and, depending upon the metal, can be very valuable.'

But how do you make a bacterium magnetic? Bacteria are usually grown in the laboratory on a growth medium containing simple sugars. Dr Alistair Dean, a microbiologist at Oxford University, gave some bacteria a sugar that was bound to a phosphate molecule. In order to use the sugar, the bacteria had to secrete an enzyme to split it from the phosphate. The sugar was then absorbed by the bacterium, while the phosphate remained outside the cell.

Phosphate is relatively insoluble. If the solution contains dissolved metals, these will form precipitates with phosphate on the nearest available surface - in this case the bacteria. If the metal is magnetic, then it is a simple job to harvest the bacteria by passing a current through some steel wool. Professor Ellwood and his colleagues first tested this with solutions containing radioactive isotopes common in effluents produced by British Nuclear Fuels. Typically, concentrations of uranium, caesium, strontium and other radioactive metals were reduced by a factor of 20.

However, not all metals readily form insoluble phosphates, and the next step was to find a similar way of removing these from solution. The organism they struck upon was a bacterium called Desulphovibrio. This organism is common in places where there is no oxygen for respiration. Its respiration is based, rather, on sulphate. The sulphate ion (one sulphur atom plus four oxygen atoms) is taken into the cell, the oxygen removed and sulphur released, usually as hydrogen sulphide. Sulphide is highly insoluble, so if there are any metals in the solution, these are precipitated on to the cell surface.

The results, Professor Ellwood admits, were a complete surprise. When tested on a large volume of industrial effluent containing two parts per million mercury, a pilot system for a company in the Netherlands succeeded in reducing the concentration to five parts per billion: a reduction of more than 99 per cent.

The chemical mechanism is not clear, but it seems that the bacteria become covered with a 'feather boa' of iron sulphide strands. This massive surface area - more than 200 square metres per gram - makes it extremely efficient at mopping up stray metals. The irony of this case is that the company decided it was cheaper to pay the fine for discharging the untreated effluent than invest in a new treatment plant. So much for leaving environmental control to market forces.

By contrast, some of these metals, such as rhodium, are extremely valuable. Jim Watson is presently assessing the feasibility of using natural populations of Desulphovibrio to clean up the sediments of New York harbour.

'The value of the recovered metals in this situation,' Professor Ellwood says, 'could potentially pay for the entire process.' Laboratory tests suggest that any industry that uses precious metals - the photographic processing industry, for example - might be able to profit from using magnetic bacteria systems to recycle waste metals.

It is a tempting prospect: companies not so much penalised for polluting as able to profit from good environmental practice. With extensive trials under way at Southampton General Hospital to exploit the same system in treating victims of nuclear accidents, the potential of these magnetic bacteria may be limited only by the ingenuity of biotechnologists.

(Photograph omitted)

Start your day with The Independent, sign up for daily news emails
ebooks
ebooksA celebration of British elections
  • Get to the point
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

SThree: Trainee Recruitment Consultant - Dublin

£13676.46 - £16411.61 per annum + OTE: SThree: SThree Trainee Recruitment Cons...

Ashdown Group: Marketing or Business Graduate Opportunity - Norwich - £22,000

£18000 - £22000 per annum + training: Ashdown Group: Business and Marketing Gr...

SThree: Trainee Recruitment Consultant

£20000 - £25000 per annum + Commission: SThree: Are you great at building rela...

Ashdown Group: Database Analyst - Birmingham - £22,000 plus benefits

£20000 - £22000 per annum + excellent benefits: Ashdown Group: Application Sup...

Day In a Page

General Election 2015: Ed Miliband's unlikely journey from hapless geek to heart-throb

Miliband's unlikely journey from hapless geek to heart-throb

He was meant to be Labour's biggest handicap - but has become almost an asset
Amr Darrag: Ex-Muslim Brotherhood minister in exile still believes Egypt's military regime can be replaced with 'moderate' Islamic rule

'This is the battle of young Egypt for the future of our country'

Ex-Muslim Brotherhood minister Amr Darrag still believes the opposition can rid Egypt of its military regime and replace it with 'moderate' Islamic rule, he tells Robert Fisk
Why patients must rely less on doctors: Improving our own health is the 'blockbuster drug of the century'

Why patients must rely less on doctors

Improving our own health is the 'blockbuster drug of the century'
Sarah Lucas is the perfect artist to represent Britain at the Venice Biennale

Flesh in Venice

Sarah Lucas has filled the British pavilion at the Venice Biennale with slinky cats and casts of her female friends' private parts. It makes you proud to be a woman, says Karen Wright
11 best anti-ageing day creams

11 best anti-ageing day creams

Slow down the ageing process with one of these high-performance, hardworking anti-agers
Fishing for votes with Nigel Farage: The Ukip leader shows how he can work an audience as he casts his line to the disaffected of Grimsby

Fishing is on Nigel Farage's mind

Ukip leader casts a line to the disaffected
Who is bombing whom in the Middle East? It's amazing they don't all hit each other

Who is bombing whom in the Middle East?

Robert Fisk untangles the countries and factions
China's influence on fashion: At the top of the game both creatively and commercially

China's influence on fashion

At the top of the game both creatively and commercially
Lord O’Donnell: Former cabinet secretary on the election and life away from the levers of power

The man known as GOD has a reputation for getting the job done

Lord O'Donnell's three principles of rule
Rainbow shades: It's all bright on the night

Rainbow shades

It's all bright on the night
'It was first time I had ever tasted chocolate. I kept a piece, and when Amsterdam was liberated, I gave it to the first Allied soldier I saw'

Bread from heaven

Dutch survivors thank RAF for World War II drop that saved millions
Britain will be 'run for the wealthy and powerful' if Tories retain power - Labour

How 'the Axe' helped Labour

UK will be 'run for the wealthy and powerful' if Tories retain power
Rare and exclusive video shows the horrific price paid by activists for challenging the rule of jihadist extremists in Syria

The price to be paid for challenging the rule of extremists

A revolution now 'consuming its own children'
Welcome to the world of Megagames

Welcome to the world of Megagames

300 players take part in Watch the Skies! board game in London
'Nymphomaniac' actress reveals what it was really like to star in one of the most explicit films ever

Charlotte Gainsbourg on 'Nymphomaniac'

Starring in one of the most explicit films ever