Humboldt-Universität zu Berlin - Mikrobiologie

Humboldt-Universität zu Berlin | Institut für Biologie | Mikrobiologie | Hengge group | Publications | Complete list of original research publications

Complete list of original publications

Original research publications


Douny, L., J.I. Hernández Lobato, A. Séré, S. Sawadogo, and R. Hengge (2023) The Hunter shirt: the role of Acacia nilotica in fermentative textile dyeing. Acta Hortic. 1361. doi: 10.17660/ActaHortic.2023.1361.8.


Junkermeier, E. H., & Hengge, R. (2021). A Novel Locally c-di-GMP-Controlled Exopolysaccharide Synthase Required for Bacteriophage N4 Infection of Escherichia coli. mBio, 12(6), e0324921.


Ziege, R., A.-M. Tsirigoni, B. Large, D.O. Serra, K.G. Blank, R. Hengge, P. Fratzl, and C.M. Bidan (2021). Adaptation of E. coli biofilm growth, morphology and mechanical properties to substrate water content. ACS Biomat. Sci. Engin. 7: 5315-5325. doi: 10.1021/acsbiomaterials.1c00927.


Pruteanu, M., Hernández Lobato, J. I., Stach, T., & Hengge, R. (2020). Common plant flavonoids prevent the assembly of amyloid curli fibres and can interfere with bacterial biofilm formation. Environ Microbiol., 22(12), 5280–5299.


Richter, A. M., Possling, A., Malysheva, N., Yousef, K. P., Herbst, S., von Kleist, M., & Hengge, R. (2020). Local c-di-GMP Signaling in the Control of Synthesis of the E. coli Biofilm Exopolysaccharide pEtN-Cellulose. J Mol Biol. , 432(16), 4576–4595.


Rodríguez-Rojas, A., Kim, J. J., Johnston, P. R., Makarova, O., Eravci, M., Weise, C., Hengge, R., & Rolff, J. (2020). Non-lethal exposure to H2O2 boosts bacterial survival and evolvability against oxidative stress. PLoS genetics, 16(3), e1008649.


Kettles, R., N. Tschowri, K. Lyons, P. Sharma, R. Hengge, M. Webber, and D. Grainger (2019) The Escherichia coli MarA protein regulates the ycgZ-ymgABC operon to inhibit biofilm formation. Mol. Microbiol. 112: 1609-1625. doi: 10.1111/mmi.14386.


Pfiffer, V., O. Sarenko, A. Possling, and R. Hengge (2019) Genetic dissection of Escherichia coli's master diguanylate cyclase DgcE: Role of the N-terminal MASE1 domain and direct signal input from a GTPase partner system. PLoS Genet., 15(4): e1008059. doi:10.1371/journal.pgen.1008059


Serra, D.O. and Regine Hengge (2019) A c-di-GMP-Based Switch Controls Local Heterogeneity of Extracellular Matrix Synthesis which Is Crucial for Integrity and Morphogenesis of Escherichia coli Macrocolony Biofilms. J. Mol. Biol. doi: 10.1016/j.jmb.2019.04.001.


Midha, A., K. Janek, A. Niewienda, P. Henklein, S. Guenther, D.O. Serra, J. Schlosser, R. Hengge, and S. Hartmann (2018) The intestinal roundworm Ascaris suum releases antimicrobial factors which interfere with bacterial growth and biofilm formation. Frontiers Cell. Infect. Microbiol. 8: 271. doi: 10.3389/fcimb.2018.00271.


Klauck, G., D.O. Serra, A. Possling, and R. Hengge (2018) Spatial organisation of different sigma factor activities and c-di-GMP signalling within the 3D landscape of a bacterial biofilm. Open Biol. 8: 180066. doi: 10.1098/rsob.180066.


Herbst, S., M. Lorkowski, O. Sarenko, T.K.L. Nguyen, T. Jaenicke, and R. Hengge (2018) Transmembrane redox control and proteolysis of PdeC, a novel type of c-di-GMP phosphodiesterase. EMBO J. 37: e97825. doi: 10.15252/embj.201797825.


Thongsomboon, W., D.O. Serra, A. Possling, C. Hadjineophytou, R. Hengge and L. Cegelski (2018) Phosphoethanolamine cellulose: a naturally produced chemically modified cellulose. Science 359: 334-338. doi: 10.1126/science.aao4096.

Highlighted by:

(1) Galperin, M.Y. and D.N. Shalaeva (2018) A bacterial coat that is not pure cotton. Science 359: 276-277.

(2) Nature highlights: How bacteria make their fortresses. d41586-018-00977-8 (Jan 18, 2018)

(3) Hamers, L.: The secret to icky, sticky bacterial biofilms lies in the microbes´ cellulose. Science News. (Jan 18, 2018)

(4) Yirka, B.: Bacterial biofilm cellulose found to differ from plant cellulose. Phys.Org. (Jan 19, 2018)

(5) Arnaud, C.H.: Bacteria can make modified cellulose. Chem. Engin. News 96: 8. (Jan 22, 2018)

(6) Golden, M.: Stanford-led team discovers new cellulose that could have applications from energy to medicine. Stanford News Service (Jan 19, 2018)

(7) Forschungsteam schafft neue Möglichkeiten für Medizin und Materialwissenschaft. Humboldt-Universität zu Berlin, Presseportal (Jan 23, 2018)

(8) Nester, G.: In F1000Prime, 12 February 2018. DOI: 10.3410/f.732501572.793542371

(9) Whitfield, C.: In F1000Prime, 16 February 2018. DOI: 10.3410/f.732501572.793542459


Sarenko, O., G. Klauck, F.M. Wilke, V. Pfiffer, A.M. Richter, S. Herbst, V. Kaever, and R. Hengge (2017) More than enzymes that make and break c-di-GMP - the protein interaction network of GGDEF/EAL domain proteins of Escherichia coli. mBio 8, e01639-17. doi: 10.1128/mBio.01639-17.

Highlighted in Faculty of 1000s:

(1) Sondermann H: In F1000Prime, 19 October 2017. DOI: 10.3410/f.731966577.793537737;

(2) Galperin M: In F1000Prime, 20 October 2017. DOI:10.3410/f. 731966577.793537754.


Serra, D.O., F. Mika, A.M. Richter, and R. Hengge (2016) The green tea polyphenol EGCG inhibits E. coli biofilm formation by impairing amyloid curli fibre assembly and down-regulating the biofilm regulator CsgD via the sE-dependent sRNA RybB. Mol. Microbiol., 101, 136–151, doi: 10.1111/mmi.13379.


Povolotsky, T.L., and R. Hengge (2015) Genome-based comparison of c-di-GMP signaling in pathogenic and commensal Escherichia coli strains. J. Bacteriol., 198,111-26, doi: 10.1128/JB.00520-15. doi: 10.1128/JB.00520-15.


Serra, D.O., G. Klauck, and R. Hengge (2015) Vertical stratification of matrix production is essential for physical integrity and architecture of macrocolony biofilms of Escherichia coli. Env. Mic. 17, 5073-88. doi: 10.1111/1462-2920.12991. doi: 10.1111/1462-2920.12991.


Hengge, R., M.Y. Galperin, J.-M. Ghigo, M. Gomelsky, J. Green, K.T. Hughes, U. Jenal, and P. Landini (2015) Systematic nomenclature for GGDEF and EAL domain-containing c-di-GMP turnover proteins in Escherichia coli. J. Bacteriol., 98, 7-11. doi: 10.1128/JB.00424-15.


Yousef, K.P., A. Streck, C. Schütte, H. Siebert, R. Hengge, and M. von Kleist (2015) Logical-continuous modelling of post-translationally regulated bistability of curli fiber expression in Escherichia coli. BMC Syst. Biol. 23, 39. doi: 10.1186/s12918-015-0183-x.


Richter, A.M., T.L. Povolotsky, L.H. Wieler, and R. Hengge (2014) C-di-GMP signaling and biofilm-related properties of the Shiga toxin-producing 2011 German outbreak Escherichia coli O104:H4. EMBO Mol Med., 6, 1622-37. doi: 10.15252/emmm.201404309.


Serra, D.O., A.M. Richter, and R. Hengge (2013) Cellulose as an architectural element in spatially structured Escherichia coli biofilms. J. Bacteriol. 195, 5540-5554. doi: 10.1128/JB.00946-13.


Lindenberg, S., G. Klauck, C. Pesavento, E. Klauck, and R. Hengge (2013) The EAL protein YciR is a trigger enzyme in a c-di-GMP signaling cascade in E. coli biofilm control. EMBO J. 32, 2001-2014. doi:10.1038/emboj.2013.120

(Highlighted in EMBO J: Jenal, U. (2013) Think globally, act locally: How bacteria integrate local decisions with their global cellular programme. EMBO J. 32, 1972-1974;

Highlighted in Faculty of 1000s: Sondermann H: In F1000Prime, 31 May 2013;


Serra, D.O., A.M. Richter, G. Klauck, F. Mika, and R. Hengge (2013) Microanatomy at cellular resolution and spatial order of physiological differentiation in a bacterial biofilm. MBio 4(2), e00103-13. doi: 10.1128/ mBio.00103-13.

(Highlighted by S. Molloy in: Nature Rev. Microbiol. 11 (2013), 300-301).


Tschowri, N., and R. Hengge (2012) Molecular function and potential evolution of the biofilm-modulating blue light-signaling pathway of Escherichia col. Mol. Microbiol. 85, 893-906. doi: 10.1111/j.1365-2958.2012.08147.x.


Mika, F., S. Busse, A. Possling, J. Berkholz, N. Tschowri, N. Sommerfeldt, M. Pruteanu, and R. Hengge (2012) Targeting of csgD by the small regulatory RNA RprA links stationary phase, cell envelope stress and biofilm formation in Escherichia coli. Mol. Microbiol. 84, 51-65. doi: 10.1111/j.1365-2958.2012.08002.x


Pesavento, C., and R. Hengge (2012) The global repressor FliZ antagonizes gene expression by sS–containing RNA polymerase due to overlapping DNA binding specificity. Nucl. Acids Res. 40, 4783-4793. doi: 10.1093/nar/gks055


Kolmsee, T., and R. Hengge (2011) Rare codons play a positive role in the expression of the stationary phase sigma factor (RpoS) sS in Escherichia coli. RNA Biol. 8, 913-921.


Singh, S.S., A. Typas, R. Hengge, and D.C. Grainger (2011) Sigma-70 domain 3 senses sequence and conformation of the promoter spacer region. Nucl. Acids Res. 39, 5109-5118.


Basineni, S.R., R. Madhugiri, T. Kolmsee, R. Hengge, and G. Klug (2009) The influence of Hfq and ribonucleases on the stability of the small non-coding RNA OxyS and its target rpoS in E. coli is growth phase dependent. RNA Biol. 6, 584-594.


Sommerfeldt, N., A. Possling, N. Tschowri, G. Becker, C. Pesavento, H. Weber, and R. Hengge (2009) Gene expression patterns and differential input into curli fimbriae regulation of all GGDEF/EAL domain proteins in Escherichia coli. Microbiology 155, 1318-1331.


Tschowri, N., S. Busse, and R. Hengge (2009) The BLUF-EAL protein YcgF acts as a direct anti-repressor in a blue light stress response of E.coli. Genes Dev. 23, 522-534.


Pesavento, C., G. Becker, N. Sommerfeldt, A. Possling, N. Tschowri, A. Mehlis, and R. Hengge (2008) Inverse regulatory coordination of motility and curli-mediated adhesion of E.coli. Genes Dev. 22, 2434-2446.


Heuveling, J., A. Possling, and R. Hengge (2008) A role for Lon protease in the control of acid resistance genes in Escherichia coli . Mol. Microbiol. 69, 534-547. 


Obrist, M., S. Milek, E. Klauck, R. Hengge, and F. Narberhaus (2007) Region 2.1 of the Escherichia coli heat shock sigma factor RpoH (s32) is necessary but not sufficient for degradation by the FtsH protease. Microbiology 153, 2560-2571.


Barembruch, C., and R. Hengge (2007) Cellular levels and activity of the flagellar sigma factor FliA of Escherichia coli are regulated by FlgM-modulated proteolysis. Mol. Microbiol. 65, 76-89.


Typas, A., C. Barembruch, A. Possling, and R. Hengge (2007) Stationary phase reorganisation of the E.coli transcription machinery by Crl protein, a fine-tuner of sS activity and levels. EMBO J. 26, 1569-1578.


Typas, A., S. Stella, R.C. Johnson, and R. Hengge (2007) The –35 sequence location and the Fis-sigma factor interface determine sS selectivity of the proP(P2) promoter in Escherichia coli. Mol. Microbiol. 63, 780-796.


Weber, H., C. Pesavento, A. Possling, G. Tischendorf, and R. Hengge (2006) Cyclic-diGMP signaling within the sS network of Escherichia coli. Mol. Microbiol. 62, 1014-1034.

(HIghlighted by S. Molloy in: Nature Rev. Microbiol. 4 (2006), 878-879).


Santos, J.M., P. Freire, F. Mika, R. Hengge, and C.M. Arraiano (2006) Bacterial polyadenylation links transcription and mRNA degradation. Mol. Microbiol. 60, 177-188.


Typas, A., and R. Hengge (2006) Role of the spacer between the -35 and -10 region in sS promoter selectivity in Escherichia coli. Mol. Microbiol. 59, 1037-1051.


Mika, F., and R. Hengge (2005) A two-component phosphotransfer network involving ArcB, ArcA and RssB coordinates synthesis and proteolysis of sS in Escherichia coli. Genes Dev. 19, 2770-2781.


Backfisch, T., M. Pruteanu, R. Hengge, E.D. Gilles (2005) Mathematical modeling of RpoS regulation in E.coli. Foundations of Systems Biology and Engineering, 239-242.


Weber, H., T. Polen, J. Heuveling, V. Wendisch, and R. Hengge (2005) Genome-wide analysis of the general stress response network in Escherichia coli: sS-dependent genes, promoters and sigma factor selectivity. J. Bacteriol. 187, 1591-1603.


Typas, A., and R. Hengge (2005) Differential ability of sS and s70 of Escherichia coli to utilise promoters containing half or full UP-element sites. Mol. Microbiol. 55, 250-260.


Metzner, M., J. Germer, and R. Hengge (2004) Multiple stress signal integration in the regulation of the complex sS-dependent csiD-ygaF-gabDTP operon in Escherichia coli. Mol. Microbiol. 51, 799-811.


Stephani, K., D. Weichart, and R. Hengge (2003) Dynamic control of Dps protein levels by the ClpXP and ClpAP proteases in Escherichia coli. Mol. Microbiol.49, 1605-1614.


Stüdemann, A., M. Noirclerc-Savoye, E. Klauck, G. Becker, D. Schneider, and R. Hengge (2003) Sequential recognition of two distinct elements in sS (RpoS) by the proteolytic targeting factor RssB and the ClpX chaperone. EMBO J. 22, 4111-4120.


Weichart, D., N. Querfurth, M. Dreger, and R. Hengge-Aronis (2003) A global role for ClpP-containing proteases in stationary phase adaptation of Escherichia coli. J. Bacteriol. 185, 115-125.


Pruteanu, M., and R. Hengge-Aronis (2002) The cellular level of the recognition factor RssB is rate-limiting for sS proteolysis: Implications for RssB regulation and signal transduction in sS turnover in Escherichia coli. Mol. Microbiol. 45, 1701-1714.


Germer, J., G. Becker, M. Metzner, and R. Hengge-Aronis (2001) Role of activator site position and a distal UP-element half-site for sigma factor selectivity at a CRP/H-NS-activated sS-dependent promoter in Escherichia coli. Mol. Microbiol. 41, 705-716.


Klauck, E., M. Lingnau, and R. Hengge-Aronis (2001) Role of the response regulator RssB in sS recognition and initiation of sS proteolysis in Escherichia coli. Mol. Microbiol. 40, 1381-1390.


Becker, G., and R. Hengge-Aronis (2001) What makes an Escherichia coli promoter sS-dependent? Role of the -13/-14 nucleotide promoter positions and region 2.5 of sS. Mol. Microbiol. 39, 1153-1165.


Balandina, A., L. Claret, R. Hengge-Aronis, and J. Rouvière-Yaniv (2001) The Escherichia coli histone-like protein HU regulates rpoS translation. Mol. Microbiol. 39, 1069-1079.


Colland, F., M. Barth, R. Hengge-Aronis, and A. Kolb (2000) Sigma factor selectivity of Escherichia coli RNA polymerase: role for CRP, IHF and Lrp transcription factors. EMBO J. 19, 3028-3037.


Becker, G., E. Klauck, and R. Hengge-Aronis (2000) The response regulator RssB, a recognition factor for sS proteolysis in Escherichia coli, can act like an anti-sS factor. Mol. Microbiol. 35, 657-666.


Biran, I., L. Klimentiy, R. Hengge-Aronis, E.Z. Ron, and J. Rishpon (1999) On-line monitoring of gene expression. Microbiology 145, 2129-2133.


Becker, G., E. Klauck, and R. Hengge-Aronis (1999) Regulation of RpoS (sS) proteolysis in Escherichia coli: The response regulator RssB is a recognition factor that interacts with the turnover element in RpoS. Proc. Natl. Acad. Sci. USA 96, 6439-6444.


Fischer, D., A. Teich, P. Neubauer, and R. Hengge-Aronis (1998) The general stress sigma factor sS is induced during the diauxic lag phase of Escherichia coli grown on glucose and lactose. J. Bacteriol. 180, 6203-6206.


Zhang, A., S. Altuvia, A. Tiwari, R. Hengge-Aronis and G. Storz (1998) The oxyS regulatory RNA represses translation of the sS subunit of RNA polymerase by titrating HF-I activity. EMBO J. 17, 6061-6068.


Bouvier, J., S. Gordia, G. Kampmann, R. Lange, R. Hengge-Aronis, and C. Gutierrez (1998) Interplay between global regulators of Escherichia coli: effect of RpoS, H-NS and Lrp on transcription of the gene osmC. Mol. Microbiol. 28, 971-980.


Germer, J., A. Muffler, and R. Hengge-Aronis (1998) Trehalose is not relevant for  in-vivo activity of sS-containing RNA polymerase in Escherichia coli. J. Bacteriol. 180, 1603-1606.


Marschall, C., V. Labrousse, M. Kreimer, D. Weichart, A. Kolb, and R. Hengge-Aronis (1998) Molecular analysis of the regulation of csiD, a carbon starvation-inducible gene in Escherichia coli that is exclusively dependent on sS and requires activation by cAMP-CRP and Lrp. J. Mol. Biol. 276, 339-353.


Bouché, S., E. Klauck, D. Fischer, M. Lucassen, K. Jung, and R. Hengge-Aronis (1998) Regulation of RssB-dependent proteolysis in Escherichia coli: A role for acetyl phosphate in a response regulator-controlled process. Mol. Microbiol. 27, 787-795.


Klauck, E., J. Böhringer, and R. Hengge-Aronis (1997) The LysR-like regulator LeuO in Escherichia coli is involved in the translational regulation of rpoS by affecting the expression of the small regulatory DsrA-RNA, and is itself under the control of H-NS. Mol. Microbiol. 25, 559-569.


Beglova, N., D. Fischer, R. Hengge-Aronis, and K. B. Gehring (1997) 1H, 15N and 13C NMR assignments, secondary structure and overall topology of the Escherichia coli GlgS protein. Eur. J. Biochem. 246, 301-310.


Muffler, A., M. Barth, C. Marschall, and R. Hengge-Aronis (1997) Heat shock regulation of sS turnover: A role for DnaK and relationship between stress responses mediated by sS and s32 in Escherichia coli. J. Bacteriol. 179, 445-452.


Muffler, A., D.D. Traulsen, R. Lange, and R. Hengge-Aronis (1997) The RNA-binding protein HF-I plays a global regulatory role which is largely but not exclusively due to its role in the expression of the sS subunit of RNA polymerase in Escherichia coli. J. Bacteriol. 179, 297-300.


Muffler, A., D. Fischer, and R. Hengge-Aronis (1996) The RNA-binding protein HF-I, known as a host factor for phage Qb RNA replication, is essential for the translational regulation of rpoS in Escherichia coli. Genes Dev. 10, 1143-1151.


Muffler, A., D.D. Traulsen, R. Lange, and Hengge-Aronis, R. (1996) Posttranscriptional osmotic regulation of the sS subunit of RNA-polymerase in Escherichia coli. J. Bacteriol. 178, 1607-1613.


Muffler, A., D. Fischer, S. Altuvia, G. Storz, and R. Hengge-Aronis (1996) The response regulator RssB controls stability of the sS subunit of RNA-polymerase in Escherichia coli. EMBO J. 15, 1333-1339.


Marschall, C. and R. Hengge-Aronis (1995) Regulatory characteristics and promoter analysis of csiE, a stationary phase-inducible gene under positive control of sS and the cAMP-CRP complex in Escherichia coli. Mol. Microbiol. 18, 175-184.


Lange, R. and R. Hengge-Aronis (1995) Identification of transcriptional start sites and the role of ppGpp in the expression of rpoS, the structural gene for the sS subunit of RNA-polymerase in Escherichia coli. J. Bacteriol. 177, 4676-4680.


Barth, M., C. Marschall, A. Muffler, D. Fischer, and R. Hengge-Aronis (1995) A role for the histone-like protein H-NS in growth phase-dependent and osmotic regulation of sS and many sS-dependent genes in Escherichia coli. J. Bacteriol. 177, 3455-3464.


Böhringer, J., D. Fischer, G. Mosler, and R. Hengge-Aronis (1995) UDP-glucose is a potential intracellular signal in the control of sS and sS-dependent genes in Escherichia coli. J. Bacteriol. 177, 413-422.


Lange, R. and R. Hengge-Aronis (1994) The nlpD gene is located in an operon with rpoS on the Escherichia coli chromosome and encodes a novel lipoprotein with a potential function in cell wall formation. Mol. Microbiol. 13, 733-743


Lange, R. and R. Hengge-Aronis (1994) The cellular concentration of the sS subunit of RNA-polymerase in Escherichia coli is controlled at the levels of transcription, translation and protein stability. Genes Dev. 8, 1600-1612.


Lange, R., M. Barth and R. Hengge-Aronis (1993) Complex transcriptional control of the stationary phase-induced and osmotically regulated sS-dependent osmY (csi-5) gene suggests novel roles for Lrp, IHF and cAMP-CRP in the stationary phase response in Escherichia coli. J. Bacteriol. 175, 7910-7917.


Weichart, D., R. Lange, N. Henneberg and R. Hengge-Aronis (1993) Identification and characterization of stationary phase-inducible genes in Escherichia coli. Mol. Microbiol. 10, 408-420.


Hengge-Aronis, R., R. Lange, N. Henneberg and D. Fischer (1993) Osmotic regulation of rpoS-dependent genes in Escherichia coli. J. Bacteriol. 175, 259-265.


Hengge-Aronis, R. and D. Fischer (1992) Identification and molecular analysis of glgS, a novel growth phase-regulated and rpoS-dependent gene involved in glycogen synthesis in Escherichia coli. Mol. Microbiol. 6, 1877-1886.


Hengge-Aronis, R., W. Klein, R. Lange, M. Rimmele and W. Boos (1991) Trehalose synthesis genes are controlled by the putative sigma factor encoded by rpoS and are involved in stationary phase thermotolerance in Escherichia coli. J. Bacteriol. 173, 7918-7924.


Lange, R. and R. Hengge-Aronis (1991) Growth phase-regulated expression of bolA and morphology of stationary phase Escherichia coli cells is controlled by the novel sigma factor sS (rpoS). J. Bacteriol. 173, 4474-4481.


Lange, R. and R. Hengge-Aronis (1991) Identification of a central regulator of stationary phase gene expression in Escherichia coli. Mol. Microbiol. 5, 49-59.


Hengge-Aronis, R. and W. Boos (1986) Translational control of exported proteins in Escherichia coli. J. Bacteriol. 167, 462-466.


Hengge, R. (1986) Studies of secretion of periplasmic proteins in Escherichia coli. Dissertation, Universität Konstanz. Hartung-Gorre Verlag, Konstanz. 


Hengge, R. and W. Boos (1985) Defective secretion of maltose- and ribose-binding proteins caused by a truncated periplasmic protein in Escherichia coli. J. Bacteriol. 162, 972-978.


Hengge, R., T.J. Larson, and W. Boos (1983) sn-Glycerol-3-phosphate transport in Salmonella typhimurium. J. Bacteriol. 155, 186-195.


Larson, T.J., D. Ludtke, R. Hengge, and W. Boos (1982) sn-Glycerol- 3-phosphate transport in Escherichia coli and Salmonella typhimurium. Tokai J. Exp. Clin. Med. 7, Supplement, 149-155.


Brass, J.M., W. Boos, and R. Hengge (1981) Reconstitution of maltose transport in malB mutants of Escherichia coli through calcium-induced disruptions of the outer membrane. J. Bacteriol. 146, 10-17.