Phycocyanin alpha-subunit phycocyanobilin lyase

Phycobiliproteins, unlike other light-harvesting proteins involved in photosynthesis, bear covalently attached chromophores. The bilin chromophores are attached through thioether bonds to cysteine residues. The cyanobacterium Synechococcus sp. PCC 7002 has eight distinct bilin attachment sites on seven polypeptides, all of which carry the same chromophore, phycocyanobilin. When two genes in the phycocyanin operon of this organism, cpcE and cpcF, are inactivated by insertion, together or separately, the surprising result is elimination of correct bilin attachment at only one site, that on the alpha subunit of phycocyanin. We have overproduced CpcE and CpcF in Escherichia coli. In vitro, these proteins catalyze the attachment of phycocyanobilin to the alpha subunit of apophycocyanin at the appropriate site, alpha-Cys-84, to form the correct adduct. CpcE and CpcF also efficiently catalyze the reverse reaction, in which the bilin from holo-alpha subunit is transferred either to the apo-alpha subunit of the same C-phycocyanin or to the apo-alpha subunit of a heterologous C-phycocyanin. The forward and reverse reactions each require both CpcE and CpcF and are specific for the alpha-Cys-84 position. Phycocyanobilin is the immediate precursor of the protein-bound bilin.

Sequence diversity within the argF, fbp and recA genes of natural isolates of Neisseria meningitidis: interspecies recombination within the argF gene

Studies of natural populations of Neisseria meningitidis using multilocus enzyme electrophoresis have shown extensive genetic variation within this species, which, it has been proposed, implies a level of sequence diversity within meningococci that is greater than that normally considered as the criterion for species limits in bacteria. To obtain a direct measure of the sequence diversity among meningococci, we obtained the nucleotide sequences of most of the argF, recA and fbp genes of eight meningococci of widely differing electrophoretic type (from the reference collection of Caugant). Sequence variation between the meningococcal strains ranged from 0-0.6% for fbp, 0-1.3% for argF, and 0-3.3% for recA. These levels of diversity are no greater than those found within Escherichia coli 'housekeeping' genes and suggest that multilocus enzyme electrophoresis may overestimate the extent of nucleotide sequence diversity within meningococci. The average sequence divergence between the Neisseria meningitidis strains and N. gonorrhoeae strain FA19 was 1.0% for fbp and 1.6% for recA. The argF gene, although very uniform among the eight meningococcal isolates, had a striking mosaic structure when compared with the gonococcal argF gene: two regions of the gene differed by greater than 13% in nucleotide sequence between meningococci and gonococci, whereas the rest of the gene differed by less than 1.7%. One of the diverged regions was shown to have been introduced from the argF gene of a commensal Neisseria species that is closely related to Neisseria cinerea. The source of the other region was unclear.

Substitution of arginine for glycine 325 in the collagen alpha 5 (IV) chain associated with X-linked Alport syndrome: characterization of the mutation by direct sequencing of PCR-amplified lymphoblast cDNA fragments

A large kindred with adult-type X-linked Alport syndrome was studied with regard to a defect in the recently described COL4A5 collagen gene. Southern blot analysis with COL4A5 cDNA probes showed loss of a MspI restriction site. Direct sequencing of cDNA amplified from lymphoblast mRNA demonstrated a single-base substitution converting a glycine codon to arginine at position 325 in the alpha 5 chain of type IV collagen. The triple-helical collagenous domain of alpha 5(IV), characterized by a Gly-X-Y repeat sequence, is interrupted 22 times by noncollagenous sequences. The mutation creates an additional interruption in the Gly-X-Y repeat motif, between interruptions 4 and 5. It is interesting that such glycine substitutions inside the COL1A1 or COL1A2 genes have been associated with many cases of osteogenesis imperfecta. This gly325-to-arg substitution presumably alters the triple-helix formation, and, in turn, modifies the ultrastructural and functional characteristics of the type IV collagen network inside the glomerular basement membrane.

Different mutations in the COL4A5 collagen gene in two patients with different features of Alport syndrome

Alport syndrome is a hereditary renal disease in which progressive renal failure is often accompanied by sensorineural deafness and ocular abnormalities. Recently, mutations were detected in the type IV collagen alpha 5 chain gene in Alport syndrome patients. We searched for mutations in this gene in 18 unrelated patients, and in two patients abnormalities were detected. In the gene of patient BB we identified a complex deletion, which included the exons encoding the non-collagenous domain and part of the collagenous region. This patient showed early onset nephritis (end-stage renal disease at 17 years) with deafness. Within a year after receiving a kidney from an unrelated donor, he developed an antiglomerular basement membrane nephritis. In patient WJ a point-mutation was detected, changing a tryptophane into a serine in the non-collagenous domain. His clinical features are milder (renal failure at 33 years, no hearing loss), and a recent renal allograft did not provoke antiglomerular basement membrane disease. These initial data suggest that differences in the extent of disruption of the non-collagenous domain may correlate with the severity and/or heterogeneity of Alport syndrome and with the development of nephritis in renal allografts.

Complete amino acid sequence of the human alpha 5 (IV) collagen chain and identification of a single-base mutation in exon 23 converting glycine 521 in the collagenous domain to cysteine in an Alport syndrome patient

We have generated and characterized cDNA clones providing the complete amino acid sequence of the human type IV collagen chain whose gene has been shown to be mutated in X chromosome-linked Alport syndrome. The entire translation product has 1,685 amino acid residues. There is a 26-residue signal peptide, a 1,430-residue collagenous domain starting with a 14-residue noncollagenous sequence, and a Gly-Xaa-Yaa-repeat sequence interrupted at 22 locations, and a 229-residue carboxyl-terminal noncollagenous domain. The calculated molecular weight of the mature alpha 5(IV) chain is 158,303. Analysis of genomic DNA from members of a kindred with Alport syndrome revealed a new HindIII cleavage site within the coding sequence of one of the cDNA clones characterized. The proband had a new 1.25-kilobase HindIII fragment and a lack of a 1.35-kilobase fragment, and his mildly affected female cousin had both alleles. The mutation which was located to exon 23 was sequenced from a polymerase chain reaction-amplified product, and shown to be a G----T change in the coding strand. The mutation changed the GGT codon of glycine 521 to cysteine. The same mutation was found in one allele of the female cousin. The results were confirmed by allele-specific hybridization analyses.

Anatomical relationships in the patterns of insulin-like growth factor (IGF)-I, IGF binding protein-1, and IGF-I receptor gene expression in the rat kidney

The rat kidney is both a target of circulating insulin-like growth factor-I (IGF-I) and a site of local IGF-I production. In order to identify which renal structures produce IGF-I and the functionally related IGF binding protein 1 (IGFBP-1), and which structures are potential sites of circulating or endogenous renal IGF action, we have employed in situ hybridization to localize IGF-I, IGFBP-1, and IGF-I receptor messenger RNAs (mRNAs) in the rat kidney. The effects of hypophysectomy (Hx) and GH replacement on renal IGF-I, IGFBP-1, and IGF-I receptor gene expression have also been evaluated. IGF-I and IGFBP-1 mRNAs are both localized in the epithelial cells of medullary thick ascending limbs (TALs) of Henle's loops in the normal rat kidney. IGF-I receptor mRNA is also abundant in TALs, but, in addition, is distributed throughout the distal nephron and collecting duct, and in the glomerulus, with lowest levels found in proximal tubules. Hx and GH treatment had complex effects on patterns of renal IGF-I and IGFBP-1 gene expression. In general, Hx resulted in decreased IGF-I and increased IGFBP-1 mRNA levels, and GH treatment produced the opposite effects, while IGF-I receptor mRNA levels were not significantly effected by either treatment. However, the most dramatic effect produced by the interruption of the pituitary-renal axis was the demonstration of reciprocal changes in IGF-I vs. IGFBP-1 gene expression in individual kidneys and even in individual nephrons, suggesting a local interaction between IGF-I and IGFBP-1 in the regulation of their respective mRNA levels. Functional implications issuing from these anatomical relationships in renal patterns of IGF-I, IGFBP-1, and IGF-I receptor gene expression are that IGF-I, if secreted into the tubular lumen, possibly carried or modulated by IGFBP-1, may act on luminal TAL and downstream receptor sites. The specific physiological role of IGF-I produced in TALs is open to speculation. Glomerular IGF-I receptor sites, based on their localization upstream and distant from local sources of IGF-I production, are predicted to be targets for circulating IGFs.

Mutation in the alpha 5(IV) collagen chain in juvenile-onset Alport syndrome without hearing loss or ocular lesions: detection by denaturing gradient gel electrophoresis of a PCR product

A single base mutation was identified in the type IV collagen alpha 5 chain gene (COL4A5) of a Danish kindred with Alport syndrome. The 27-year-old male proband developed hematuria in childhood and terminal renal failure at the age of 25 years. He has no hearing loss or ocular lesions. Electron microscopy demonstrated splitting of the lamina densa of the glomerular basement membrane. The proband's mother has had persistent microscopic hematuria since the age of 40 years, but no other manifestations. Southern analysis of MspI-digested genomic DNA from the proband showed the absence of 1.3-kb and 0.9-kb fragments present in control DNA but the presence of a 2.2-kb variant fragment, indicating the loss of an MspI restriction site in the 3' end of the gene. The mother had all three fragments, indicating heterozygosity. PCR amplification of exon 14 (counted from the 3' end) and subsequent denaturing gradient gel electrophoresis analysis suggested a sequence variant in the proband and his mother. This was confirmed by sequencing of the PCR-amplified exon 14 region of the hemizygous proband, which demonstrated the base change G----A abolishing an MspI restriction site. Hybridization analysis with allele-specific probes confirmed the inheritance of the mutation with the phenotype. The mutation changed the GGC codon for glycine-1143 to GAC for aspartate. Substitution of glycine-1143, located in the collagenous domain of the alpha 5(IV) chain, for any other amino acid can be expected to interfere with the maintenance of the triple-helical conformation of the collagen molecule. This could, in turn, weaken the glomerular-basement-membrane framework and lead to increased permeability.

Metabolic differences and similarities of selenium in blood and brain of the rat following the administration of different selenium compounds

A common intermediate, i.e., selenite, was found in the serum of the rat; the maximum levels occurred 3 h after administration independent of chemical forms. This indicates that both the reduction of selenate to selenite, and oxidation of seleno-dl-methionine to selenite existed in the metabolic pathways of the rat. We found that water-soluble selenium compounds led to a similar maximum content in blood and serum, but seleno-dl-methionine had a higher affinity for the brain and, by gel filtration chromatography, for the higher mol-wt (25-100 K Da) fractions of serum protein, when compared with inorganic forms.

muI Na+ channels expressed transiently in human embryonic kidney cells: biochemical and biophysical properties

We describe the transient expression of the rat skeletal muscle muI Na+ channel in human embryonic kidney (HEK 293) cells. Functional channels appear at a density of approximately 30 in a 10 microns 2 patch, comparable to those of native excitable cells. Unlike muI currents in oocytes, inactivation gating is predominantly (approximately 97%) fast, although clear evidence is provided for noninactivating gating modes, which have been linked to anomalous behavior in the inherited disorder hyperkalemic periodic paralysis. Sequence-specific antibodies detect a approximately 230 kd glycopeptide. The majority of molecules acquire only neutral oligosaccharides and are retained within the cell. Electrophoretic mobility on SDS gels suggests the molecules may acquire covalently attached lipid. The channel is readily phosphorylated by activation of the protein kinase A and protein kinase C second messenger pathways.

Inactivated whole-virus vaccine derived from a proviral DNA clone of simian immunodeficiency virus induces high levels of neutralizing antibodies and confers protection against heterologous challenge

We tested the ability of macaques vaccinated with inactivated whole simian immunodeficiency virus (SIV) to resist challenge with either homologous or heterologous cell-free uncloned SIV administered by the intravenous route. The vaccine virus was derived from a proviral DNA clone and thus was considered genetically homogeneous. Sixteen macaques received either hepatitis B surface antigen (n = 6) or the inactivated whole-SIV vaccine (n = 10) at weeks 0, 4, and 49 of the study. All SIV vaccine recipients developed high levels of homologous and heterologous neutralizing antibodies in response to vaccination. At the time of challenge (week 53), vaccinees were further stratified to receive either homologous (n = 10) or heterologous (n = 6) uncloned live SIV. The envelope glycoproteins of the homologous and heterologous challenge viruses were 94% and 81% identical to the vaccine virus, respectively. Regardless of challenge inoculum, all vaccinees in the control group (hepatitis B surface antigen) became infected, whereas all SIV vaccinees were protected against detectable infection. These data support the concept that an efficacious vaccine for HIV might be possible, and suggest that genetic variation of HIV might not be an insurmountable obstacle for vaccine development.

Role of interspecies transfer of chromosomal genes in the evolution of penicillin resistance in pathogenic and commensal Neisseria species

The two pathogenic species of Neisseria, N. meningitidis and N. gonorrhoeae, have evolved resistance to penicillin by alterations in chromosomal genes encoding the high molecular weight penicillin-binding proteins, or PBPs. The PBP 2 gene (penA) has been sequenced from over 20 Neisseria isolates, including susceptible and resistant strains of the two pathogenic species, and five human commensal species. The genes from penicillin-susceptible strains of N. meningitidis and N. gonorrhoeae are very uniform, whereas those from penicillin-resistant strains consist of a mosaic of regions resembling those in susceptible strains of the same species, interspersed with regions resembling those in one, or in some cases, two of the commensal species. The mosaic structure is interpreted as having arisen from the horizontal transfer, by genetic transformation, of blocks of DNA, usually of a few hundred base pairs. The commensal species identified as donors in these interspecies recombinational events (N. flavescens and N. cinerea) are intrinsically more resistant to penicillin than typical isolates of the pathogenic species. Transformation has apparently provided N. meningitidis and N. gonorrhoeae with a mechanism by which they can obtain increased resistance to penicillin by replacing their penA genes (or the relevant parts of them) with the penA genes of related species that fortuitously produce forms of PBP 2 that are less susceptible to inhibition by the antibiotic. The ends of the diverged blocks of DNA in the penA genes of different penicillin-resistant strains are located at the same position more often than would be the case if they represent independent crossovers at random points along the gene. Some of these common crossover points may represent common ancestry, but reasons are given for thinking that some may represent independent events occurring at recombinational hotspots.

[Kinetics of pharmacologic effects of radix Aconiti Lateralis Preparata and sini decoction]

In the study of analgesic action of Radix Aconiti Lateralis Preparata and Sini Decoction hot-plate method was used and the time-effect relationship was determined. The biological half-lives were 11.05 h and 6.84 h respectively. In the study of the effect on inflammation induced by egg white in the ankle joints of rats, the method of complement ED50 was used. The residual rates of the dosages after an interval of 6 hours were 0.60 and 0.69, and the biological half-lives were 8.11 h and 11.35 h respectively.

Combination median filter

A detail- and structure-preserving smoothing filter is introduced. It is called the combination median filter as it uses directional median, multilevel median, and median filters to smooth different regions of the image. The decision about the region is made by robust Dixon's r-test which is well known in statistics for outlier detection. The threshold value of Dixon's test can be kept constant. As a result, the filtering algorithm operates like a quasi-nonadaptive filter, and no computation of local statistics is involved. Some properties of the filter as well as detailed experimental results that demonstrate its superior performance are presented.

EXPRESSION OF C-fos PROTEIN IN SEROTONERGIC NEURONS OF RAT BRAINSTEM FOLLOWING ELECTRO-ACUPUNCTURE

The c-fos proto-oncogene encodes a nuclear phosphoprotein, Fos which has been proposed to be a "third messenger" coupling short term extracellular signals to long term alteration in cell function. Using double labeling immunocytochemistry, the present work demonstrated the co-localization of Fos protein and serotonin in the nucleus raphe dorsalis, nucleus raphe centralis superior and rostral ventromedial medulla. The results pose an interesting problem, the possible relation of Fos protein to the biosynthesis of serotonin, awaiting further investigation.

Decreased transforming growth factor-beta response and binding in insulin-independent teratoma-derived cell lines with increased tumorigenic properties

The mouse C3H teratoma-derived cell line 1246 is an adipogenic cell line which stringently requires insulin to proliferate and differentiate in defined medium. From this cell line an insulin-independent cell line called 1246-3A was isolated. It was found that, in contrast to 1246 cells, 1246-3A cells had lost the ability to differentiate and became tumorigenic when injected at a density of 10(6) cells/mouse into syngeneic host C3H mice. In addition, they produce in their culture medium transforming growth factor alpha- and beta-like polypeptides which stimulate their proliferation. Highly tumorigenic insulin-independent cell lines able to give rise to tumor when injected at a density of 10(4) cells/mouse were isolated by using an in vitro-in vivo shuttle technique. The highly tumorigenic cell lines have lost the response to TGF-beta 1. The binding of TGF-beta 1 to the nontumorigenic parent cell line or to cells displaying increased tumorigenic properties was investigated. The data presented here indicate that the increased tumorigenicity is accompanied by a progressive decrease of specific binding of TGF-beta 1 to the cells. However, the decreased number of cell surface TGF-beta 1 binding sites in the highly tumorigenic cells did not correlate with an increase in the secretion of TGF-beta protein by the tumorigenic cells, as all of TGF-beta produced by the cells was in a latent form. Affinity cross-linking experiments indicated that the 1246 cell line displayed several TGF-beta cross-linked molecular species (MW 140, 92, and 70 kDa). Increase of tumorigenicity was accompanied by a marked decrease in the intensity of the cross-linked bands, particularly of the 92 and 70 kDa species.

Abnormal renal response to twenty-four-hour dehydration and fasting in Nagase analbuminemic rats

We assessed renal function in fasting adult Nagase analbuminemic rats (NAR). Sodium output in male and female NAR was 68% and 46%, respectively, of the output of age- and sex-matched normal Sprague-Dawley (SD) rats. Potassium excretion was significantly greater in female NAR but there was no difference between male NAR and SD rats. The renal clearances of urea and creatinine were reduced in NAR with corresponding increases in plasma concentrations; however, the urea and creatinine concentrations were not different in plasma samples taken from normally fed and hydrated SD and NAR rats. Exchangeable body sodium and sodium space was significantly larger in normally fed and hydrated NAR than in SD but there were no differences in plasma sodium concentrations or plasma volumes. Although plasma concentrations of albumin in NAR were only about 0.07% of the concentration in SD rats, the renal clearance of albumin in NAR was threefold greater. Kidney weights in NAR were 10 to 16% less than in SD rats but liver weights were 22 to 42% greater. Clearly, renal function was markedly abnormal in Nagase rats during a 24-hour fast.

Cellular pattern of insulin-like growth factor-I (IGF-I) and IGF-I receptor gene expression in the developing and mature ovarian follicle

We have employed in situ hybridization histochemistry to map the cellular pattern of insulin-like growth factor-I (IGF-I) and IGF-I receptor gene expression in developing rat ovaries from the time of birth through adulthood, and in response to hypophysectomy and gonadotropin replacement. From the early postnatal period, both IGF-I and IGF-I receptor messenger RNAs (mRNAs) were highly abundant and evenly distributed in granulosa cells of small, growing follicles. In large follicles, however, IGF-I gene expression was heterogeneous. IGF-I mRNA was most abundant in granulosa cells lining the antrum and surrounding the oocyte, but was low or undetectable in mural granulosa cells of Graafian follicles, and was also undetectable in luteinized granulosa cells of corpora lutea. IGF-I receptor mRNA was evenly distributed in developing and mature follicles and was highly abundant in the luteinized granulosa cells of corpora lutea. IGF-I receptor but not IGF-I mRNA was detected in growing oocytes. Hypophysectomy resulted in a decrease and treatment with PMSG resulted in an increase in follicular IGF-I receptor mRNA levels, whereas there was no change in IGF-I mRNA levels in the same protocol. In summary, high levels of both IGF-I and IGF-I receptor gene expression occur in the granulosa cells of actively growing follicles, suggesting that granulosa cell IGF-I may have a role in follicular or oocyte growth. IGF-I gene expression is lost concomitant with follicular enlargement and granulosa cell differentiation, whereas IGF-I receptor gene expression continues at high levels in luteinized granulosa cells, suggesting that IGF effects on differentiated granulosa cell function are due to circulating, not local, hormone. Finally, granulosa cell IGF-I receptor gene expression appears to be regulated by the gonadotropin present in pregnant mare serum.

Identification of the nuclear localization signal of human papillomavirus type 16 L1 protein

Human papillomavirus type 16(HPV16) L1 and L2 capsid proteins can be detected only in the nucleus of infected cells. For other nuclear proteins, specific sequences of basic amino acids(aa) termed nuclear localization signals (NLS) direct the protein from the cytoplasm to the nucleus. We used a series of deletion and substitution mutations of the HPV16 L1 protein, produced by recombinant vaccinia virus (rVV), to identify NLS within HPV16 L1 and showed that HPV16 L1 contains two NLS sequences, each containing basic aa clusters. One NLS consisted of 6 basic amino acids (KRKKRK from aa 525 to 530) at the carboxy terminal end of L1. The other NLS contained 2 basic aa clusters(KRK from aa 510 to 512 and KR at aa 525, 526) separated by 12 amino acids. Mutations in either NLS did not alter nuclear localization of L1 when the other remained intact, but mutations to both prevented nuclear localization of L1. The L1 NLS could be overridden by introduction of a membrane binding sequence at the amino terminal end of the protein. A databases search showed that all sequenced papillomaviruses are predicted to have L1 and L2 capsid proteins with sequences of basic amino acids homologous with one or both NLS of HPV16 L1.

The hygromycin-resistance-encoding gene as a selection marker for vaccinia virus recombinants

Hygromycin B (Hy), an inhibitor of RNA translation, was shown to block the replication of vaccinia virus (VV) in cultured cell lines. Insertion of the Escherichia coli Hy resistance-encoding gene (hph) into the VV genome under control of early or late synthetic VV promoters could overcome inhibition of viral replication. When hph was inserted into VV in tandem with the human papillomavirus type 16 (HPV16) L1 open reading frame, hph recombinant viruses could be selected which expressed HPV16 L1.

Expression of vaccinia recombinant HPV 16 L1 and L2 ORF proteins in epithelial cells is sufficient for assembly of HPV virion-like particles

A recombinant vaccinia virus termed pLC201VV was designed to coexpress the L1 and L2 late genes of human papillomavirus type 16 (HPV16). Synthesis of the L1 and L2 proteins occurred in cells infected with pLC201VV, and 40-nm virus-like particles with a density of 1.31 g/ml were produced in the nuclei of cells synthesizing both L1 and L2, but not in cells synthesizing either protein alone. Virus-like particles were partially purified from infected cells by sucrose gradient sedimentation and shown to consist of capsomeres similar to HPV and contain glycosylated L1 viral capsid protein. The production of HPV-like particles using recombinant vaccinia virus should be useful for biochemical studies and could provide a safe source of material for the development of a vaccine.

The value of sonography in the assessment of cholecystolithotripsy

To assess the reliability of ultrasound in measuring a minimum stone fragment burden we implanted radiolucent human gallstone fragments measuring from less than 1 mm up to 4 mm in size into the gallbladders of 12 domestic piglets. Forty-eight hours later the fragments in each animal were assessed by a qualified radiologist using two different ultrasound machines in a randomized blinded fashion. With regard to size estimation using a 5 MHz sector scanner, in two out of 12 examinations there was an overestimation of fragment size such that in a clinical setting an unneccessary repeat lithotripsy session would have been requested. A 5 MHz linear array transducer was of sufficient reliability in all size estimations not to have resulted in such a request. No gallbladder was falsely declared fragment free. There were nonshadowing fragments present in five of 12 examinations using both transducers. Clumping of small fragments less than or equal to 3 mm was present in two examinations. We recommend that a second ultrasound examination is performed when the presence of clumping is suspected and also when a fragment-free gallbladder is initially diagnosed.

Treatment of small cell lung cancer

During a 28-year period, 110 patients with small cell lung cancer were treated at our hospital. Fifty-nine patients received surgery, and 58 patients (including 7 cases after exploratory thoracotomy) received chemotherapy and/or radiotherapy. The 5-year survival rate of the surgically treated group was 17%, while none in the non-surgical group survived for more than 5 years.

Horizontal transfer of multiple penicillin-binding protein genes, and capsular biosynthetic genes, in natural populations of Streptococcus pneumoniae

Multiply antibiotic-resistant serotype 23F isolates of Streptococcus pneumoniae are prevalent in Spain and have also been recovered recently in the United Kingdom and the United States. Analysis of populations of these isolates by multilocus enzyme electrophoresis, and restriction endonuclease cleavage electrophoretic profiling of penicillin-binding protein (PBP) genes, has demonstrated that these isolates are a single clone (Muñoz et al., 1991). Here we report studies of non-serotype 23F penicillin-resistant pneumococci isolated in Spain and the United Kingdom. One of the isolates expressed serotype 19 capsule but was otherwise indistinguishable from the serotype 23F clone on the basis of multilocus enzyme electrophoresis, antibiotic resistance profiling, and restriction endonuclease patterns of genes encoding PBP1A, PBP2B and PBP2X, a result which suggests that horizontal transfer of capsular biosynthesis genes had occurred. These same techniques revealed that six other resistant isolates, all expressing serotype 9 polysaccharide capsule, represent a clone. Interestingly, the chromosomal lineage of this clone is not closely related to the 23F clone; however, the serotype 9 and 23F clones harbour apparently identical PBP1A, -2B and -2X genes. To explain these data, we favour the interpretation that horizontal gene transfer in natural populations has distributed genes encoding altered forms of PBP1A, -2B and -2X to distinct evolutionary lineages of S. pneumoniae.