snapshots malaria vaccine trial on

SCIENCE & TECHNOLOGY

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18 THE HINDU THURSDAY, NOVEMBER 15, 2012CHENNAI

Poor adult health due to childhood abuse The psychological scars of childhood abuse can havelong-term negative physical effects, as well as emotionalones, well into adulthood.

Easing cancer symptoms by massageA new study shows that a type of ancient footmassage can help cancer patients manage theirsymptoms and perform daily tasks.

Necessity is the mother ofnatural selection. When

conditions become threaten-ing, maverick or mutantmembers of a group whichcan cope with the threat sur-vive and multiply. The latestexample is the discovery of aspecial type of bacteria in theocean, which join together toform a long conducting nano-wire cable to transport elec-trons and capture the oxygenat the surface for metabolicuse. This wire is not made ofmetal, alloy or other usualmaterial, but of living biolog-ical cells. The report by Dr.Christian Pfeiffer and othersin the 8 November 2012 issueof Nature is a live example ofthe Panchatantra tale whichteaches the value of cooper-ation between individuals towin over a problem.

All organisms gain energyfor living through metabo-lism. The vital step in theprocess is the burning or ox-idation of the food molecules.Chemists define oxidation as

the loss of electrons and re-duction as the gain of elec-trons. We burn our food bythe breathing of oxygen in theair. When we oxidize our foodand gain energy, the oxygenmolecule is reduced by ac-cepting or gaining electronsto make water, while the foodmolecule is oxidized by losingelectrons; this is not muchdifferent from burning petrolfor energy.

What if no oxygen?What about organisms that

live in places where there isno oxygen? They too metabo-lize their food through oxida-tion. But, rather than oxygen,they utilize whatever elec-tron-acceptor molecules areavailable in the environment.One such group lives in ma-rine sediments, below thesurface, and it use the sul-phates in the sediment as theelectron-acceptors for ‘burn-ing’ and gaining energy, anexample of making do withavailable resources. In the

process, however, the sul-phate gains electrons and isreduced all the way to hydro-gen sulphide (H2S), a poison-ous material. How then is thissulphide removed?

The problemLook at the problem. If H2S

can be oxidized to sulphur,the situation turns safer. Butin the process electrons areliberated and should be ac-cepted by a partner. If onlyoxygen at the surface can be

reached and the electronstransferred to it, we will haveH2S becoming S and the O2

reduced to H 2O. How doesone transfer the electronscentimetres away? It is nolonger a process within thecell where reactions happenwithin nanometres, and theoxidant and reductant mole-cules are in contact. What isneeded is an efficient method— an electrical cable or wirefor transporting the electronsfrom the sulphide to the ox-

ygen above. It is here that biology

springs an unexpected sur-prise. In the sedimental layerbeneath the marine surfacelives a class of anaerobic bac-teria called Desulfobulba-ceae, which Pfeffer andcolleagues find to denselypopulate the sediments. Andthese live not as individualsbut in groups strung togetheras long, multicellular fil-aments or rods, some as longas 1.5 centimetres. And thesefilaments reach out from thesulphide-rich sedimental lay-er to the aerobic top layer afew centimetres above, whichhas dissolved oxygen (fromthe air). These filaments thusconnect the anoxic layers tothe oxic layer. And what dothey do? They capture theelectrons generated when theH2S is oxidized to S at thebottom, and transport themall the way to the oxygen atthe top, which accepts themand generates water or H2O.In other words, the Desulfo-bulbaceae bacteria line up tomake a live wire.

The researchers conducteda series of experiments toshow how the filaments formand work. They layered thesedimental layer below in the

lab and covered is with theoverlying oxic sea water andstudied the process. As thesulphide oxidation happenedin the deeper anoxic layers,distinct change in the pH wasnoticed, confirming the proc-ess. And when they gently dis-turbed the layer, they foundthe 12-15 run long fibrous fil-aments entangled. Geneticanalysis of the filamentsshowed their identity as Des-ulfobulbaceae. It appears thatat least 40 million cells cometogether to assemble fil-aments of lengths as much as1.5 cm, showing that the bac-teria could span the length ofthe entire anoxic layer.

Liquid-filled layerElectron microscopy

showed that the cells wereconnected lengthwise, andeach cell had a liquid-filledlayer in the periplasmic spacebetween the outer and innercytoplasmic membranes.These liquid compartmentsformed ridges connecting theeach cell to its neighbour,suggesting electron transportoccurring through this fluidtubular structure coveredwith a continuous outermembrane along the filamentacting as the insulator — the

ancient precursor, if you will,of the electric cable of today.Hair-like appendages, calledpili, of some bacteria areknown to be electron trans-porters, but the whole cellacting so, and joining withothers to make a conductingwire is novel, and reported forthe first time.

Plenty of roomThe physicist Richard

Feynman famously remarkedthat there is plenty of room atthe bottom. Bacterial fil-aments acting as electric na-nowires is but one example.Some cyanobacteria calledAnabena, which are able to‘fix’ nitrogen, also form suchcontinuous periplasmic fil-aments. And when a fluores-cent protein was engineeredinto some its cells, the fluo-rescence was found to movealong the filament from onecell to the other. Here is anexample of material transfer,while with Desulfobulbaceae,it is electrons that are trans-ported. Surely there is farmore room at the bottom, andnanotechnologists can learn alesson or two from suchbacteria.

D. BALASUBRAMANIANdbala@lvpei.org

INGENUOUS NATURE: The conducting nanowire cableis not made of metal, alloy or other usual material,but of living biological cells. — PHOTO: S. THANTHONI

Bacteria that line up to make a ‘live wire’ The bacteria form a long conductingnanowire cable to transport electronsand capture the oxygen at thesurface for metabolic use

SPEAKING OF SCIENCE

SNAPSHOTS

A new study using brevetoxin-2, acompound produced naturally bymarine algae, stimulated nervecell growth and plasticity inmouse neurons. Treatment forstroke may not be far off.

Stroke recovery usingmarine algae product

K. RAMESH BABU

Two professors at the Universityof California, Riverside havedeveloped a new method thatdoubles the efficiency of wirelessnetworks and could have a largeimpact on the mobile Internet andwireless industries.

Increasing efficiency ofwireless networks

M. KARUNAKARAN

Using a regional climate modeland the output of three globalclimate models, researchers atThe City College of New Yorkpredict how climate change wouldchange the face of Greenland overthe next century.

Climate change willalter Greenland’s face

REUTERS

Researchers have created a newartificial lens that is nearlyidentical to the natural lens of thehuman eye. This innovation mayprovide a natural performance inimplantable lenses to replacedamaged human eye lenses.

New, more natural lensinspired by human eye

S. SIVA SARAVANAN

On November 13, the sun emitteda mid-level solar flare. Solar flaresare powerful bursts of radiation,which can disturb the atmospherein the layer wherecommunications and GlobalPositioning System signals travel.

Sun emits a mid-levelflare on November 13

AFP

NASA and British Antarctic Surveyscientists have reported thatmarked changes to Antarctic seaice drift caused by changing windsare responsible for observedincreases in Antarctic sea icecover in the past two decades.

Why Antarctic sea icecover has increased

REUTERS

The results of thePhase III trial of themalaria vaccineRTS,S/AS01 are

greatly disappointing. The ef-ficacy of the vaccine in pre-venting clinical and severemalaria in infants aged 6 to 12weeks is much less than whatwas expected. In fact, the levelof protection offered is nearlyhalf of what was reported lastyear in older children (5 to 17months).

Vaccine efficacyThe vaccine efficacy (in in-

fants aged 6-12 weeks) wasabout 31 per cent in the caseof clinical malaria and 37 percent in the case of severe ma-laria. In the case of older chil-dren (5 to 17 months),reported last year, the protec-tion offered was nearly 56 percent in the case of clinical ma-laria and about 47 per cent forsevere malaria. The efficacyagainst severe malaria in boththe groups combined wasnearly 35 per cent. Totally,6,537 infants were studied.

The current data on infantsis also lower than what wasseen in the Phase II trial re-sults from three of the 11 cen-tres. The protection againstclinical malaria was 61.6 percent. According to Nature,nearly 60 per cent of clinicalmalaria cases were reportedfrom just two of the 11 sites.The trial is being conductedin 11 centres across sevencountries in Africa.

What then could havecaused a severe drop in theprotection efficacy? One ofthe possibilities could be the

severity of malaria transmis-sion. The Phase II resultswere from three centres thathad only low to moderate ma-laria transmission. In the caseof the Phase III, it also in-cluded centres that had highmalaria transmission. The re-al implications of vaccine pro-tection in high malariatransmission areas will beclear when the complete datais analysed in 2014 after a 30-month follow-up.

What is more disappointingis the drastic reduction in effi-cacy during the 12-month fol-low-up period. The efficacy

was “higher at the beginningthan at the end of the follow-up period” found the study,published a few days ago inThe New England Journal ofMedicine. If the protectionefficacy does wane with time,several factors may makeyounger infants more vulner-able than older children, thepaper suggests.

Possible reasonsWhat then could be the

possible reasons for the dis-appointing protection levelsseen? One could be the lowerprotection in areas that had

higher malaria transmission.Another could be the differ-ence in immune response be-tween the infants and theolder children included in thetrial. Evidence favouring thiswas earlier seen during thetrial. The co-administrationof other vaccines along withthe malaria vaccine could beanother. Finally, the presenceof maternal antibodies in in-fants could have played a rolein protecting them (both thevaccine and control groups)from malaria, thereby reduc-ing the differences seen in thetwo groups.

The vaccine has been de-veloped primarily for infantsand children in sub-SaharanAfrica. The reasons are obvi-ous: of the 216 million cases ofmalaria and 6,55,000 malar-ia-related deaths in 2010, amajority of deaths took placein African countries.

Even as many newspaperswent overboard last yearbased on results from the ol-der age group, the 2011 Edi-torial accompanying thepaper in The New EnglandJournal of Medicine explicit-ly stated: “there does notseem to be a clear scientificreason why this trial has beenreported with less than halfthe efficacy results available.”

The 2011 paper concludedwith a rider that the “vaccinehas the potential to have animportant effect on the bur-den of malaria in young Afri-can children.” The rider was:the “vaccine efficacy amongyounger infants and the dura-tion of protection will be crit-ical to determining how thisvaccine could be used effec-tively to control malaria.”

Target 2014In that sense, the latest re-

sults do dampen the highspirits seen last year. The lastword is yet to be pronounced.One has to wait till 2014 whenthe complete data is analysedand the outcome is known.Only then can it be said withany certainty if the vaccinewill indeed be included foruse in the African countriesas per WHO recommenda-tions. WHO had taken the un-usual decision last year whenit had “recommended” its usein the African countries asearly as 2015.

Malaria vaccine trial on African infants disappointing A drastic reduction in efficacy seen in the infants during the one-year follow-up period

R. PRASAD

DRASTIC DROP: The vaccine's malaria prevention efficacy in infants (6-12 weeks)is half of what was seen in older children (5-17 months). — PHOTO: AP

In the last week of October,the Mars rover Curiosity

announced that there was nomethane on Mars. The rover’sconclusion is only a prelimi-nary verdict, although it is al-ready controversial becauseof the implications of thegas’s discovery (ornon-discovery).

The presence of methane isan important sign to indicatethat life may have existed inthe planet’s past. The interestin the notion was increasedwhen Curiosity found signsthat water may have flowed inthe past through Gale Crater,the immediate neighbour-hood of its landing spot, afterfinding sedimentarysettlements.

The rover’s Tunable LaserSpectrometer (TLS), whichanalysed a small sample ofMartian air to come to theconclusion, had actually de-tected a few parts per billionof methane. However, recog-nising that the reading wastoo low to be significant, itsounded a “No”.

In an email to this Corre-spondent, Adam Stevens, amember of the science teamof the NOMAD instrument onthe ExoMars Trace Gas Orbi-ter due to be launched in Ja-nuary 2016, stressed: “Noorbital or ground-based de-tections have ever suggestedatmospheric levels anywhereabove 50 parts per billion, sowe are not expecting to seeanything above this level.”

At the same time, he alsonoted that the 50 parts perbillion (ppb) is not a globalaverage. The previous detec-tions of methane found thegas localised in the Tharsisvolcanic plateau, the SyrtisMajor volcano, and the polarcaps, locations the rover isnot going to visit. What con-tinues to keep the scientists

hopeful is that methane onMars seems to get replen-ished by some geochemical orbiological source.

The TLS will also have animportant role to play in thefuture. At some point, the in-strument will go into a highersensitivity-operating modeand make measurements ofhigher significance by reduc-ing errors.

It is pertinent to note thatscientists still have an incom-plete understanding ofMars’s natural history. As Mr.Stevens noted: “While notfinding methane would notrule out extinct or extant life,finding it would not necessar-ily imply that life exists or ex-isted either.”

Apart from methane, thereare very few “bulk” signaturesof life that the Martian geog-raphy and atmosphere haveto offer. Scientists are lookingfor small fossils, complex car-bon compounds and otherhydrocarbon gases, aminoacids, and specific mineralsthat could be suggestive of bi-ological processes.

While Curiosity has somefixed long-term objectives,they are constantly adaptedaccording to what the roverfinds. Commenting on itsplans, Mr. Stevens said, “Cu-riosity will move up AeolisMons, the mountain in themiddle of Gale Crater, takingsamples and analyses as itgoes.”

Curiosity is not the lastchance to look more closelyfor methane in the near fu-ture. Development of the Ex-oMars Trace Gas Orbiter(TGO), with which Mr. Ste-vens is working, is under way.A collaboration between theEuropean Space Agency andthe Russian Federal SpaceAgency, the TGO is plannedto deploy a stationary Landerthat will map the sources ofmethane and other gases onMars.

Significance ofMartian methaneVASUDEVAN MUKUNTH

Scientists in China said onTuesday they had se-

quenced the DNA of the wildbactrian camel, a threatenedspecies with an extraordinaryability to survive in extremeconditions.

The genetic code of Camel-us bactrianus ferus reveals20,821 genes, many of themproviding the metabolic toolsto cope with days withoutfood and water and a dietbased on tough desertvegetation.

Bactrian camels are de-scendants of even-toed ungu-lates which diverged from acommon ancestor around 55-60 million years ago, theyfound.

The DNA book could shed

light on the camel's ‘remarka-ble salt tolerance and unusu-al immune system,’ said thestudy, published in the jour-nal Nature Communications.

Wild bactrian camels livein the deserts of northwest-ern China and southwesternMongolia, where they endurefierce heat and bitter cold,aridity and sparse grazing.

Camels consume eighttimes more salt than cattle orsheep and have twice theblood glucose levels of otherruminants, yet do not devel-op diabetes or hypertension.

They also make unique dis-ease-fighting proteins calledheavy-chain antibodies,which interest pharmaceuti-cal engineers. —AFP

DNA study unravelssecrets of bactrian camels led the study and presented

the findings at a briefing.MRSA, or methicillin-re-

sistant staphylococcus au-reus, is a drug-resistantbacterial infection, or superb-ug, and a serious public healthproblem. When outbreaks oc-cur in hospitals it can lead tothe closure of whole wardswith many people infected.

The bug kills an estimated19,000 people in the UnitedStates per year. Althoughrates of MRSA infection havecome down significantly inBritain in recent years, it stillpresents a major threat withseveral hundred deaths a yearand high hospital costs in-volved in managing infectedpatients.

Julian Parkhill from Bri-tain's Sanger Institute, whoalso worked on the study, said

Researchers have usedDNA sequencing for the

first time to identify, analyseand put a halt to an infectiousdisease outbreak in ahospital.

The success of the tech-nique, which used fast ge-nome sequencing technologyto control an outbreak of theMRSA superbug on a babyward, suggests it could beused to control hospital bugs,salmonella and E.coli infec-tions and diseases like tuber-culosis, scientists said.

“What we have glimpsedthrough this pioneering studyis a future in which new se-quencing methods will helpus to identify, manage andstop hospital outbreaks,” saidNick Brown, an infection con-trol doctor at Addenbrooke'sHospital Cambridge, who co-

there is a “real health and costburden from hospital out-breaks” which could be signif-icantly reduced or eliminatedif they were containedswiftly.

In the study, staff at Ad-denbrooke's hospital usingroutine screening over a sixmonth period found 12 pa-tients carrying MRSA. Be-cause they were only usingstandard tests, which providelimited information, the in-fection control team was notable to tell if the 12 were partof an outbreak, or were un-connected cases that did notpresent a threat.

MRSA is a bug present inaround one per cent of thepopulation at any time, anddoes not always causeinfection.

Parkhill and Brown's team

analysed MRSA samples fromthe 12 patients with DNA se-quencing technology andfound that all the MRSA bac-teria were closely related,confirming an outbreak.

By tracing relatives andother people who had recentlinks to the hospital, they alsofound the outbreak was moreextensive than previouslythought, with twice as manypeople carrying or infectedwith the MRSA strain.

While this sequencingstudy was underway, the hos-pital's infection control teamfound a MRSA case in the spe-cial care baby unit - 64 daysafter the last MRSA patienthad left.

The team used advancedDNA sequencing to show inreal time that this strain wasalso part of the same out-

break, raising the possibilitythat a staff member was un-knowingly carrying andtransmitting the MRSAstrain.

After screening 154 staffthey found one carryingMRSA and, using DNA se-quencing, confirmed it wasthe strain linked to the out-break. The worker was quick-ly treated to eradicate thebug, and any further spreadwas stopped.

The researchers, whosefindings were published inthe Lancet Infectious Diseas-es journal, say this kind of fastgenome sequencing couldeventually form the basis forregional or national infectionsurveillance programmes de-signed to nip infectious dis-ease outbreaks in the bud. —Reuters

Genome sequencing halts superbug outbreak

TH Chennai/ CITY SETA_01 User: cojmv 11-14-2012 23:46 Color: CMYK