NITROGEN FIXATION: FUNDAMENTALS AND APPLICATIONS

Current Plant Science and Biotechnology in Agriculture

VOLUME 27

Scientific EditorR.I. Summerfield, The University ofReading, Department ofAgriculture, P.O. Box 236,Reading RG6 2AT, Berkshire, UK

Scientific Advisory BoardB.K. Barton, Agracetus Inc., Middleton, Wisconsin, USAF.e. Cannon, University ofMassachusetts at Amherst, Amherst, Massachusetts, USAH.V. Davies, Scottish Crops Research Institute, Dundee, Scotland, UK1. Denecke, University ofYork, York, UKJ. Hamblin, The University ofWestern Australia, Nedlands, WA, Australia1. Lyman Snow, Rutgers University, New Brunswick, New Jersey, USAC.P. Meredith, University ofCalifornia at Davis, Davis, California, USA1. Sprent, University ofDundee, Dundee, Scotland, UKD.P.S. Verma, The Ohio State University, Columbus, Ohio, USA

Aims and ScopeThe book series is intended for readers ranging from advanced students to senior researchscientists and corporate directors interested in acquiring in-depth, state-of-the-art knowledgeabout research findings and techniques related to all aspects of agricultural biotechnology.Although the previous volumes in the series dealt with plant science and biotechnology, theaim is now to also include volumes dealing with animals science, food science andmicrobiology. While the subject matter will relate more particularly to agricultural applica­tions, timely topics in basic science and biotechnology will also be explored. Some volumeswill report progress in rapidly advancing disciplines through proceedings of symposia andworkshops while others will detail fundamental information of an enduring nature that willbe referenced repeatedly.

The titles published in this series are listed at the end ofthis volume.

Nitrogen Fixation: Fundamentals and Applications Proceedings of the 10th International Congress on Nitrogen Fixation, St. Petersburg, Russia, May 28-June 3,1995

edited by

IGOR A. TlKHONOVICH and NIKOLAI A. PROVOROV All-Russia Research Institute for Agriculural Microbiology, St. Petersburg-Pushkin, Russia

V ASSIL Y 1. ROMANOV A.N. Bach Institute of Biochemistry, Moscow, Russia

and

WILLIAM E. NEWTON Department of Biochemistry arul Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, U.SA.

SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

A C.I.P. Catalogue record for this book is available from the Library of Congress

ISBN 978-94-010-4170-6 ISBN 978-94-011-0379-4 (eBook) DOI 10.1007/978-94-011-0379-4

Printed on acid-free paper

All Rights Reserved © 1995 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 1995 Softcover reprint ofthe hardcover lst edition 1995

No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permis sion from the copyright owner.

PARIS

10th INTERNATIONAL CONGRESS ON NITROGEN FIXATION

SUPPORTED BY:

Government ofRussian Federation, Ministry ofScience andTechnical Policy ofRussian Federation

Russian Academy ofAgricultural Sciences

Russian Academy of Sciences

St. Petersburg Mayor's Office

All-Russia Research Institute for Agricultural Microbiology

In cooperation with International Atomic Energy Agency(IAEA, Vienna, Austria)

SPONSORED BY:=OECD, Directorate for Food, Agriculture and FisheriesOCOE Co-operative Research Program: Biological Resource

Management for Sustainable Agricultural Systems

Russian Foundation for Fundamental Research

Russian Ministry for Agriculture and Food Production

International Foundation for Science

International Union ofMicrobiological Societies,Russian Society ofGeneral Microbiology

UNESCO

National Science Foundation (USA)

United States Department ofAgriculture

International Society for Plant Molecular Biology

North American Symbiotic Nitrogen Fixation Conference

Centro de Investigacion sobre Fijacion de Nitrogeno,UNAM, Cuernavaca

Morgan Scientific Inc.

"ECOS" Company

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ASSISTED BY:

S1. Petersburg Centre ofthe Russian Academy ofSciences

Moscow State University

Department ofthe Russian Academy ofAgricultural Sciences forNonchemozem Area (S1. Petersburg-Pushkin)

All-Russia Institute for Plant Protection (S1. Petersburg)

N.J. Vavilov All-Russia Plant Breeding Institute (S1. Petersburg)

A.N. Bach Institute ofBiochemistry (Moscow)

Institute ofPlant Physiology (Moscow)

Institute ofChemical Physics (Moscow Region, Chemogolovka)

Institute ofBiochemistry and Physiology ofPlants and Microorganisms (Saratov)

vi

10TH INTERNATIONAL CONGRESS ON NITROGEN FIXATION

WAS ORGANIZED BY

National Organizing Committee:

Congress Organizer: Igor Tikhonovich (St. Petersburg)

Deputy Organizers: Sergey Shestakov (Moscow), Vassily Romanov (Moscow)

Vladimir Ignatov (Saratov)Mikhail Ivanov (Moscow)Stanislav Izmailov (Moscow)Alexander Kashtanov (Moscow)Andrei Kozhemiakov (St. Petersburg)

Valery Shatilov (Moscow)Alexander Shilov (Moscow)Boris Simarov (St.Petersburg)Yevgeny Smolinsky (Moscow)Mark Vol'pin (Moscow)

INTERNATIONAL PROGRAM ADVISORY COMMITTEE

T. Bisseling (The Netherlands)H. Bothe (FRG)N.l Brewin (UK)FJ. de Bruijn (USA)1. Denarie (France)RA Dixon (UK)C. Elmerich (France)P.M. Gresshoff (USA)G. Hardarson (IAEA, Austria)R. Haselkorn (USA)G.B. Kiss (Hungary)A Kondorosi (France)I.K. Ladha (philippines)D.B. Layzell (Canada)AB. Legocki (poland)K. Lindstrom (Finland)

E.ll Lugtenberg (The Netherlands)y. Okon (Israel)l Olivares (Spain)APuhler (FRG)B.G. Rolfe (Australia)M.l Sadowsky (USA)J.I. Sprent (UK)1.G. Streeter (USA)1. Thomas (India)G.L. Truchet (France)c.P. Vance (USA)D.P.S. Venna (USA)G.C. Walker (USA)D. Werner (FRG)lP.W. Young (UK)

INTERNATIONAL STEERING COMMITfEE

W.E. Newton (USA)RH. Burris (USA)RW.F. Hardy (USA)H. Hennecke (Switzerland)

vii

R Palacios (Mexico)B.E. Smith (UK)C. Veeger (The Netherlands)

LOCAL ORGANIZING COMMITTEE

Chainnan - Igor A. Tikhonovich

Infonnation, Registration, Exhibitions and Computer Service - Elena F. Chesnokova(Head), Nikolai I. Vorobyev, Anna V. Smitskaya, Ivan A. Kniazev, Maxim Yu. Zanin,Maria Yu. Fedorova, Elena A. Dolgich, Elena V. Limeschenko, Lidia N. Sokol,Anatoly Va. Danilin, Tatiana S. Batyreva, Anna P. Fomicheva, Viktor A. Kvitko

Finance - Tatiana K. Zabotina (Head), Ioulia A. Chvabaouskene,Raisa S. Zhihareva, Olga V. Anisimova, Vera A. Tarasova

Participant Communicatons -Irina A. Kolesnik (Head), Zinaida N. Bogdanova,Viktoria B. Trofimova, Mikhail S. Bronshtein

Interpretor Services - Vladimir S. Soloviev

Publications - Nikolai A. Provorov (Head), Alexandra O. Ovtsyna,Oxana N. Kurchak, Yanina K. Zabelina

Cultural Program Activities for Participants and Guests fjointly with"PETROINTOUR") - Svetlana A. Tchetkova (Head), Anna M. Kunakova

Accomodations, Meals and Congress Facilities - Ludmila N. Paromenskaya,Olga A. Kulikova, Galina A. Vladimirova, Elena P. Andrievskaya,

Valentina V. Vikhrova

Transportation and Post-Congress Tours fjointly with"PETROINTOUR" and "NICKO TOURS") - Vladimir K. Chebotar'

Poster Session Preparations - Vladimir K. Lebsky (Head), Alex Yu. Borisov,Viktor Yeo Tsyganov, Konstantin V. Ushakov, Andrei A. Belimov,Elena V. Morzhina, Elena D. Kozlova, Galina S. Konovalova

Media Relations - Natalia I. Novikova

Congress Logo Designer - Remigius I. Chvabaouskas

Congress Film Production - Artyom Yeo Men', Yevgeniya M. Men'

Visa Arrangements - Alexandra N. Zaretskaya

Security - Mars V. Karimov, Georgy YU. Laptev

viii

PREFACE

Among the most urgent problems that face Mankind as we approach the end of the 20thcentury are providing sufficient nourishment to the constantly growing World, reducingenvironmental pollution and conserving energy. The intense interest in biologicalnitrogen fixation shown by scientists from diverse fields of research (chemists,biochemists, molecular biologists, geneticists, microbiologists, agrochemists and manyothers) is obviously connected with the fact that understanding the main steps of thisprocess will help people cope with the global problems mentioned above.

We believe that any division between fundamental and applied science is artificial; thereis really only Science and its practical applications. While developing the ScientificProgram of the 10th International Congress on Nitrogen Fixation, that is reflected bythis volume, the Organizing Committee was always mindful of the fact that nitrogenfixation presents a broad spectrum of scientific problems of high fundamental interestwhile at the same time having a very significant practical value. It is important to stressthat, even in the countries with traditionally high application ofmineral nitrogen, interestin a sustainable balanced agriculture, and thus in the application ofmicrobial inoculants,is growing. So it is easy to understand why this Congress had three of its 13 scientificsessions (7 Symposia and 6 Round Tables) devoted to applied aspects.

Among the many scientific aspects that were discussed in the Congress in S1. Petersburg,three should be mentioned because of their active development of the past several years:(l) the impact of the nitrogenase structures on efforts to understand the mechanism thatoccurs in all nitrogen-fixing microorganisms; (2) dissection of the elaborate system ofsignal exchange between plants and microorganisms that undergirds the formation of thesymbiotic apparatus responsible for the majority of biologically fixed nitrogen inagriculture; (3) our increasing knowledge about the diversity and evolution ofmicroorganisms that are able to fix nitrogen and the attempts to systematize themthorough molecular genetic techniques. The importance of the last is difficult tooverestimate - among others, this work should help to develop biological methods forprotection of plants against phytopathogens. Thus, the phenomenon of biologicalnitrogen fixation presents a wonderful model for the study of many fundamental aspectsof science in quite a number ofdifferent fields.

The 10th International Congress on Nitrogen Fixation took place in S1. Petersburg,Russia, May 28 - June 3, 1995 and was organized through the All-Russia ResearchInstitute for Agricultural Microbiology in S1. Petersburg-Pushkin. The Congress wassupported and sponsored by a wealth of organizations, both within and from outside

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Russia, as listed elsewhere in this volwne. Without their generous assistance, thisCongress could not have been organized. About 600 participants from over 60 countriesgathered to share their recent research progress with one another and to come to knowthe history and beauty of St. Petersburg. In this book, we have tried to reflect the mainquestions that were discussed in the Congress and to detail the contributions of everyparticipant. We hope this volwne will promote new insights, more significant researchand fruitful cooperation.

We thank all those listed elsewhere who participated in the organization ofthe Congress,its smooth day-to-day operation, and the preparation of this volwne. Lastly, we thankVicki Newton for her tireless efforts to keep us on our tight publication schedule and ourfamilies and friends for their love, patience, support and understanding during thisintense experience.

Saint - Petersburg,Russia, June 1995

Igor A. TikhonovichNikolai A. ProvorovVassily I. RomanovWilliam E. Newton

TABLE OF CONTENTS

SECTION 1: INTRODUCTORY AND OVERVIEW LECTURES 1

M.E. VOL'PIN, AE. SIffi..,OVChemical nitrogen fixation in solution 3

A VAN KAMMENThe molecular development ofnitrogen fixing root nodules 9

G.A. ROMANENKOContribution ofRussian scientists towards solution ofbiologicalnitrogen fixation problem 15

B.E. SMITH, S.M.ROE, F.K.YOUSAFZAIThe structures ofthe nitrogenase proteins - an overview 19

R. HASELKORNMolecular genetics of nitrogen fixation in photosyntheticprokaryotes 29

B.n. LUGTENBERG, G.Y. BLOEMBERG, AAN. VAN BRUSSEL,I.W. KIJNE, I.E., THOMAS-OATES, H.P. SPAINKSignals involved in nodulation and nitrogen fixation 37

C. GUAN, K. PAWLOWSKI, T. BISSELINGNodulation in legumes and actinorhizial plants .49

P. MERGAERT, S. GOORMACHTIG, D. GEELEN, R. GEREMIA,M. VALERIO-LEPINIEC, M. FERNANDEZ-LOPEZ, K. GOETHALS,W. D'HAEZE, I.-c. PROME, F.I. DE BRUUN, M. VANMONTAGU,M. HOLSTERSEarly events in the Azorhizobium cau/inodans-Sesbania rostratasymbiosis 61

I.G. STREETERIntegration ofplant and bacterial metabolism in nitrogenfixing systems 67

C.P. VANCE, P.R. GRAHAMNitrogen fixation in agriculture: Application and perspectives 77

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xii

SECTION 2: CHEMISTRY AND BIOCHEMISTRY OF NITROGENASES.87

B.E. SMITHNitrogenase - after the structure 89

W.E. NEWTON, K FISHER, C.-H. KIM, l SHEN,lS. CANTWELL, KS. TIIRASHER, DR DEANProbing catalytic function through amino-acid substitutions inAzotobacter vinelandii molybdenum-dependent nitrogenase 91

L.A. SYRTSOVA, S.W. DRUZHININ, AV. KHRAMOV,AP. MORAVSKYPhotostimulation ofnitrogenase reaction in vitro forinvestigation ofnitrogenase mechanism action..................................................... 97

D.l LOWE, G.A ASHBY, M. BRUNE, H. KNIGHTS,M.R. WEBB, R.N.F. THORNELEYATP hydrolysis and energy transduction by nitrogenase l03

L.M. CAMERON, BJ. HALESCO inhibition ofnitrogen fixation l09

AE.SHll.,OVNitrogenase and its chemical models 115

R.A HENDERSONMechanistic studies on iron-sulfur-based clusters 117

D. SELLMANNChemistry ofN2H2 and other nitrogen hydrids related to N2fixation in the coordination sphere ofmetal sulfur complexes 123

GJ. LEIGHThe chemical mechanism ofbiological nitrogen fixation and thechemistry ofmodel systems 129

D. COUCOUVANIS, P.E. MOSIER, S. MALINAK,L. LAUGHLIN, KD. DEMANDISCatalytic reduction ofhydrazine and acetylene to ammonia andethylene and stoichiometric reduction ofCN to ammonia andmethane by Fe/M/S clusters (M=Mo, V) with structural featuressimilar to those of the FelMo/S site in nitrogenase 137

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POSTER SUMMARIES 143

SECTION 3: REGULATION OF NITROGEN FIXATION 165

C. KENNEDY, S. SlIESTAKOVRegulation ofnitrogen fixation: Progress and prospects 1995 167

R.A. DIXON, S. AUSTIN, T. EYDMANN, T. JONES,E. SODERBACK, S. HILLRegulation ofnitrogen fixation by theNlFL and NIFAproteins from Azotobacter vinelandii 171

YP. ZHANG, S.K. GRUNWALD, D. LIES, C. HALBLEID,Y MA, G.P. ROBERTS, R.H. BURRIS, P.W. LUDDENPosttranslational regulation ofnitrogenase activity byreversible ADP-ribosylation; how are the regulatory enzymesDRAT and DRAG regulated? 177

PA KAMINSKI, N. MICHEL-REYDELLET, N. DESNOUES,C. ELMERICHRegulation of free-living and symbiotic nitrogen fixation inAzorhizobium caulinodans 183

M.l. MERRICK, M. TAYLOR, M.H. SAIER, JR., l. REIZERThe role ofgenes downstream ofthe aN structural gene rpoNin Klebsiella pneumoniae 189

F.J. DE BRUUN, L. GRAHAM, A. MILCAMPS, D.RAGATZUse ofluciferase (Tn5-lux) reporter system to studyRhizobium meliloti genes responding to N/C/02 limitation orplant factors and their role in rhizosphere competition 195

W. KLIPP, S. ANGERMULLER, S. ASTROTH, P.-B. KAMP,M. KERN, M. KUTSCHE, S. LEIMKUHLER, A. PASCHENRegulation ofmolybdenum and alternative nitrogenases in thephotosynthetic purple bacterium Rhodobacter capsulatus 201

H. BOTHE, O. SCHMITZ, G. BOlSON, B. HUNDESHAGEN,W.ZIMMERNitrogenases and hydrogenases in cyanobacteria 207

POSTER SUMMARIES 213

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SECTION 4: SIGNALLING PROCESSES IN PLANT-MICROBEINTERACTIONS 263

1.1. SPRENTSignalling processes in plant-microbe interactions:Introductory remarks 265

1.A DOWNIE, I.M. SUTTON, G. DEAN, AE. DAVIES,C. FINNIE, S. GHELANI, E.1.A LEA, K.E. WILSON,1. FIRMINDeterminants ofnodulation efficiency in the symbiosis betweenPisum sativum and Rhizobium leguminosarum 269

F.DEBELLE,P.ROCHE,C.PL~ANET,F.~LET,C.PVI0L,

M. ARDOUREL, N. DEMONT, C. ROSENBERG, G. TRVCHET,1.C. PROME, 1. DENARIEThe genetics ofRhizobium host range control: Allelic and non-allelicvariation 275

E. MARTINEZ, T. LAEREMANS, R. POUPOT, M.A ROGEL,L. LOPEZ, F. GARCIA, 1. VANDERLEYDEN, 1.C. PROME,F.LARANod metabolites and other compounds excreted by Rhizobium spp 281

1.E. COOPER, 1.R. RAO, E. EVERAERT, L. DE COOMANMetabolism offlavonoids by rhizobia 287

D.A. PHll..LIPS, W.R. STREIT, C.M. 10SEPH, E. SANDE,1.D. PALUMBO, C.I. KADO, F.J. DE BRUIJNPlant signals to soil microbes: Regulators ofrhizospherecolonization 293

AM. HIRSCH, Y. FANG, L.M. BRILL, K.L. WYCOFF,B.M. NINER, J.P. BRANDT, P. VAN RIllJNNodule development in legumes - the early stages:Involvement ofearly nodulins, lectins, and other proteins 299

G. STACEY, E. MINAMI, H. KOVeH!, J.R. COHN,R.W. CARLSONSignal exchange during soybean nodulation byBradyrhizobium japonicum 305

POSTERS~S 311

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SECTION 5: SYMBIOTICALLY ESSENTIAL BACTERIAL GENES ANDDYNAMICS OF RHIZOBIUMGENOME 349

M.F. HYNES. M.l MITSCH, L.A. FAAS, C.K. YOSTWhat is still to be learned about the Rhizobium genomeand Rhizobium genes involved in symbiosis? 351

R. PALACIOS, M. CASTILLO, M. FLORES, G. HERNANDEZ,P. MAVINGill, D. ROMERODynamics ofthe Rhizobiumgenome 353

E. SOUPENE, M. FOUSSARD, G. TRUCHET, P. BOISTARD,l BATUTDevelopmental regulation ofnitrogen fixation geneexpression in Rhizobium meli/oti-alfalfa symbiosis .359

K. LINDSTROM, L. PAULIN, C. ROOS, L. SUOMINENNodulation genes ofRhizobium galegae 365

LA SHARYPOVA, B.V. SIMAROVIdentification ofgenes affecting symbiotic effectiveness ofRhizobium meli/oti.. 371

U.B. PRIEFER, H. PRECHELGenetic loci involved in the synthesis and exportof rhizobiallipopolysaccharides .377

L. mONY-MEYER, O. PREISIG, R. ZUFFEREY, H. HENNECKEThe role of a microaerobically induced cb-typecytochrome oxidase in symbiotic nitrogen fixation 383

Z. ZHANG, G. NONG, F. HU, X. ZHANG, X. ZOU, l ZHOU,F. LI, H. CHENThe symbiotic plasmid and nodulation genes inRhizobium huakuii Chen 389

POSTER SUMMARIES .393

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SECTION 6: PLANT RESPONSES IN SYMBIOSIS .427

AB. LEGOCKIPR proteins are differentially expressed during symbiosis .429

P.M. GRESSHOFFMoving closer to the positional cloning oflegumenodulation genes 431

G.B. KISS, P. KALO, G. CASANDI, K. FOLFOLDI,P. KISS, G. ENDREMap based cloning system inMedicago suitable for isolatinggenes involved in leafmorphogenesis, nodule formationand effectiveness ofnitrogen fixation .437

P. BAUER, T. COBADE LA PENA, F. FRUGIER, S. POIRIER,H.I. MCKHANN, P. RATET, S. BROWN, M. CRESPI,A KONDOROSIRole ofplant hormones and carbon/nitrogen metabolism incontrolling nodule initiation on alfalfa roots 443

D. WERNER, A JACOBI, T. WINZER, P. MULLERSymbiosomes under control ofplant and microsymbiont genes 449

NJ. BREWIN, L. BOLANOS, P. DAHIYA, C.D. GARDNER,L.E. HERNANDEZ, lV. KARDAILSKY, E.A RATHBUN,DJ. SHERRIERDifferentiation ofthe symbiosome compartment in pea nodule ceUs 455

lA TIKHONOVICH, A Y. BORISOV, lA CHVABAUSKENE,N.N. KAMARDIN, L.V. KRAVCHENKO, V.K. LEBSKY,F. MINCHIN, E.V. MORZHINA, Y.I. ROMANOV, L. SKOT,SA TCHETKOVA, V.E. TSYGANOVPlant genetical control at the crucial steps of symbiosis .461

D.P.S. VERMA, X. GU, Z. HONGBiogenesis ofthe peribacteroid membrane in root nodules:Roles ofdynamin and phosphatidyl-inositol-3-kinase .467

B.S. DE PATER, M.A BAUCHROWITZ, C.L. DIAZ,D.G. BARKER, G. TRUCHET, lW. KIJNEExpression of legume lectin genes 471

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K.K. SIDOROVA, V.K. SHUMNY, L.P. UZHINTSEVAGenetic experiments with pea mutants pending symbiosis studies .475

POSTER SUMMARIES 479

SECTION 7: ENERGETICS OF NITROGEN-FIXING SYSTEMS.INTEGRATION OF CARBON, NITROGENAND OXYGEN METABOLISM 519

L. COPELAND, V. ROMANOVIntegration ofcarbon and nitrogen metabolism duringplant-microbe symbioses: Introductory remarks 521

M.L. KAHN, M. MORTIMER, K.S. PARK, W. ZHANGCarbon metabolism in the Rhizobium-legume symbiosis 525

A.J. GORDONSucrose metabolism to support N2 fixation in legume root nodules 533

BT DRISCOLL, M. OSTERAS, T.M. FINANMalic enzymes ofRhizobium meliloti 539

S.J. TEMPLE, S. BAGGA, C. SENGUPTA-GOPALANRegulation and functional analysis ofglutamine synthetasegenes in legumes .545

N.N. KUDRYAVTSEVA, V.D. TSYDENDAMBAEV,P.N. DUBROVO, V.V. KRYLOVA, L.I. BORODENKO,G.YA. ZHIZNEVSKAYA, S.F. IZMAILOVRole of the peribacteroid membrane in the interactions ofthesymbiotic partners in the nitrogen-fixing root nodulesofLupinus luteus L. 551

D.A. DAY, L. WHITEHEAD, J.H.M. HENDRIKS, S.D. TYERMANNitrogen and carbon exchange across symbiotic membranes fromsoybean nodules 557

H. HAAKER, M.M. SZAFRAN, H.J. WASSINK, M.A. APPELSMalate, aspartate and proton exchange between Rhizobiumleguminosarum symbiosomes and its symbiotic partner Pisum sativum 565

POSTER SUMMARIES .573

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SECTION 8: ECOLOGY AND AGRICULTURAL APPLICATIONS OFNITROGEN-FIXING SYSTEMS (Sponsored by OECD) 617

R.W.F. HARDY, A.R.1. EAGLESHAMEcology and agricultural applications ofnitrogen-fixing systems:Overview 619

D. WERNEREcology and agricultural applications of nitrogen-fixing systems:Crops and sciences involved 621

F. O'GARA, Y. MOENNE-LOCCOZ, D.N. DOWLING, M.P. NUTIRecent developments in biotechnology and the potential impact ofnitrogen fixation in the field 623

P.M. REDDY, 1.K. LADHACan symbiotic nitrogen fixation be extended to rice? 629

Y. OKON, R. ITZIGSOHN, S. BURDMAN, M. HAMPELAdvances in agronomy and ecology of the Azospirillum/plant association 635

R.M. BODDEY, V.M. REIS, S. URQUIAGA, L.G. DA SILVA, F.B. REIS,1.1. BALDANI, 1. DOBEREINERN2 fixation in sugar cane: The role ofAcetobacter diazotrophicus 641

K. VLASSAK, P. VAN RlillN, AA FRANCO, F. WAELKENS,C. VERRETH, E. LUYTEN, 1. VANDERLEYDENThe broad host range oftwo bean nodulating rhizobia,Rhizobium tropici CIAT899 and Rhizobium sp. BR816:Field studies and genetic analysis 647

R.S. SMITHInoculant formulations and applications to meet changing needs 653

1. THOMAS, SP. PALANIAPPAN, W. HOPPER, C.B. NIRMALADevelopment ofRhizobium and Azospirillum inoculants withenhanced potential for field applications 659

S. BOUSSffiA, x. wu, N. PELEG, A ZARITSKYN2-fixing cyanobacteria as BTl toxin genes delivery system - abiotechnological approach to control malaria mosquitoes 665

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ROUND TABLE DISCUSSION (Sponsored by OECD)

N.AMARGER, W.J.BROUGHTON (Conveners).Application ofthe nitrogen fixing microorganisms in the environment 671

POSTER SUMMARIES 679

SECTION 9: ROUND TABLE DISCUSSIONS ON URGENT ISSUES 787

G.!. LIKHTENSTEIN, R.N.F. THORNELEYNitrogenase catalysis 789

F.B. DAZZO, B.G. ROLFERole ofpolysaccharides and other glycoconjugates innitrogen-fixing bacterial-plant associations 793

J.R. GALLON, C.P. WOLKNitrogen fixation in phototrophic bacteria 797

C.A. ATKINS, F.R. MINCHINOxygen as the major regulating factor in symbiotic nitrogenfixation 801

J.K. LADHA, O.P. RUPELLANitrogen fixation and sustainable agriculture 805

K. LINDSTROM, P. VAN BERKUM, M. GILLIS,E. MARTINEZ, N. NOVIKOVA, B. JARVISReport from the roundtable on Rhizobium taxonomy 807

AUTHOR INDEX. ' 811