The effect of Ai Chi aquatic therapy on individuals with knee osteoarthritis: a pilot study.

[Purpose] To examine the efficacy of Ai Chi in relieving the pain and stiffness of knee osteoarthritis and improving, physical functioning, proprioception and quality of life. [Subjects and Methods] Twenty-five persons with knee osteoarthritis completed 5 weeks Ai Chi practice (60 minutes per session, twice per week, 10 sessions in total). Knee pain and stiffness were measured before and after the intervention program. [Results] Significant improvements in pain, self-perceived physical functioning and self-perceived stiffness were observed after the Ai-Chi intervention. On average, no significant change in knee range of motion, 6-minute walk test distances or proprioception was observed. [Conclusion] A five-week Ai Chi intervention can improve the pain and stiffness of knee osteoarthritis and self-perceived physical functions and quality of life improvement. Ai Chi may be another treatment choice for people with knee OA to practice in the community.

Genetic characterization and heterologous expression of brochocin-C, an antibotulinal, two-peptide bacteriocin produced by Brochothrix campestris ATCC 43754.

Brochocin-C, produced by Brochothrix campestris ATCC 43754, is active against many strains of the closely related meat spoilage organism Brochothrix thermosphacta and a wide range of other gram-positive bacteria, including spores of Clostridium botulinum. Purification of the active compound and genetic characterization of brochocin-C revealed that it is a chromosomally encoded, two-peptide nonlantibiotic bacteriocin. Both peptides of brochocin-C are ribosomally synthesized as prepeptides that are typical of class II bacteriocins. They are cleaved following Gly-Gly cleavage sites to yield the mature peptides, BrcA and BrcB, containing 59 and 43 amino acids, respectively. Fusion of the nucleotides encoding the signal peptide of the bacteriocin divergicin A in front of the structural genes for either BrcA or BrcB allowed independent expression of each component by the general protein secretion pathway. This revealed the two-component nature of brochocin-C and the necessity for both peptides for activity. A 53-amino-acid peptide encoded downstream of brcB functions as the immunity protein (BrcI) for brochocin-C. In addition, the cloned chromosomal fragment revealed open reading frames downstream of brcI, designated brcT and brcD, that encode proteins with homology to ATP-binding cassette translocator and accessory proteins, respectively, involved in the secretion of Gly-Gly-type bacteriocins.

Characterization of a locus from Carnobacterium piscicola LV17B involved in bacteriocin production and immunity: evidence for global inducer-mediated transcriptional regulation.

Mutational, nucleotide sequence, and transcriptional analyses of a 10-kb fragment (carnobacteriocin locus) from the 61-kb plasmid of Carnobacterium piscicola LV17B demonstrated the presence of two gene clusters (cbnXY and cbnSKRTD) upstream of the previously sequenced carnobacteriocin B2 structural and immunity genes (cbnB2 and cbiB2). Deduced products of cbnK and cbnR have sequence similarity to proteins of Agr-type two-component signal transduction systems, and those of cbnT and cbnD have sequence similarity to proteins of signal sequence-independent secretion systems. Deduced products of cbnX, cbnY, and cbnS are class II-type bacteriocin precursors with potential leader peptides containing double-glycine cleavage sites. Genetic analysis indicated that the 10-kb locus contains information required for the production of, and immunity to, the plasmid-encoded carnobacteriocin B2 and the chromosomally encoded carnobacteriocin BM1. In addition, this locus is involved in the production of at least one additional antimicrobial compound and an inducer factor that plays a role in the regulation of carnobacteriocin B2. Transcription analysis indicated that the operons cbnXY, cbnB2-cbiB2, and cbnBM1-cbiBM1 (with the latter encoding carnobacteriocin BM1 and its immunity protein on the chromosome) and two small transcripts containing cbnS are transcribed only in induced cultures. These transcripts are coregulated and subject to inducer-mediated transcriptional control. Similar regulation of the cbn operons is mirrored by the similarity in the nucleotide sequence of their promoter regions, all of which contain two imperfect direct repeats resembling those in Agr-like regulated promoters upstream of the transcription start sites.

Giant linear plasmids of beta-lactam antibiotic producing Streptomyces.

A survey of the total cellular DNA from five beta-lactam antibiotic-producing Streptomyces spp. by pulsed field gel electrophoresis was conducted to investigate the presence of linear plasmids. Streptomyces clavuligerus NRRL 3585 contained two giant linear plasmids of 120 and 430 kb, in addition to the well-characterized 11.7 kb linear plasmid. Streptomyces griseus NRRL 3851 contained a single giant linear plasmid of 120 kb, and Streptomyces jumonjinensis NRRL 5741 contained two giant linear plasmids (220 and 280 kb), and two smaller linear plasmids. No plasmids were identified in Streptomyces cattleya NRRL 3841 or Streptomyces lipmannii NRRL 3584. Southern hybridization did not reveal any homology shared by these plasmids, and beta-lactam antibiotic synthesis gene clusters were located on the chromosome.

A signal peptide secretion-dependent bacteriocin from Carnobacterium divergens.

Divergicin A is a strongly hydrophobic, narrow-spectrum, nonlantibiotic bacteriocin produced by Carnobacterium divergens LV13. This strain of C. divergens contains a 3.4-kb plasmid that mediates production of, and immunity to, the bacteriocin. N-terminal amino acid sequencing of the purified divergicin A was used to locate the structural gene (dvnA). The structural gene encodes a prepeptide of 75 amino acids consisting of a 29-amino-acid N-terminal extension and a mature peptide of 46 amino acids. Directly downstream of dvnA there is a second open reading frame that encodes the immunity protein for divergicin A. Divergicin A has a calculated molecular mass of 4,223.89 Da. The molecular mass determined by mass spectrometry is 4,223.9 Da, indicating that there is no posttranslational modification of the peptide. The N-terminal extension of divergicin A has an Ala-Ser-Ala (positions -3 to -1) cleavage site and acts as a signal peptide that accesses the general export system of the cell (such as the sec pathway in Escherichia coli). This is the first bacteriocin of lactic acid bacteria to be reported that does not have dedicated maturation and secretion genes. Production of divergicin A was observed in heterologous hosts containing only the two genes associated with divergicin A production and immunity. Fusing alkaline phosphatase behind the signal peptide for divergicin resulted in the secretion of this enzyme in the periplasmic space and supernatant of E. coli.

Characterization of the protein conferring immunity to the antimicrobial peptide carnobacteriocin B2 and expression of carnobacteriocins B2 and BM1.

Cloning of a 16-kb DNA fragment from the 61-kb plasmid of Carnobacterium piscicola LV17B into plasmidless C. piscicola LV17C restores the production of the plasmid-encoded carnobacteriocin B2 and the chromosomally-encoded carnobacteriocin BM1 and restores the immune phenotype. This fragment also has sufficient genetic information to allow the expression of carnobacteriocin B2 and its immunity in a heterologous host. The gene locus (cbiB2) responsible for immunity to carnobacteriocin B2 is located downstream of the structural gene for carnobacteriocin B2 and encodes a protein of 111 amino acids (CbiB2). CbiB2 was expressed in Escherichia coli as a fusion of the maltose-binding protein and CbiB2. The fusion protein was purified on an amylose column and cleaved with factor Xa, and pure CbiB2 was isolated by high-performance liquid chromatography. The N-terminal amino acid sequence and mass spectrometry (molecular weight [mean +/- standard error], 12,662.2 +/- 3.4) of the purified protein agree with the information deduced from the nucleotide sequence of cbiB2. Western blot (immunoblot) analysis indicates that the majority of the intracellular pool of this immunity protein is in the cytoplasm and that a smaller proportion is associated with the membrane. CbiB2 confers immunity to carnobacteriocin B2, but not to carnobacteriocin BM1, when it is expressed in homologous or heterologous hosts. No protective effect is observed for sensitive cells growing in the presence of the bacteriocin when the immunity protein is added to the medium. The purified immunity protein does not show significant binding to microtiter plates coated with carnobacteriocin B2 and is not able to inactivate the bacteriocin in solution.

Differentiation of infectious pancreatic necrosis virus isolates by polymerase chain reaction.

Infectious pancreatic necrosis virus (IPNV) from lake trout of Cornwall lake (LT-IPNV), from trout of Jasper (Ja-IPNV) and Arctic char of Northwest Territories (AC-IPNV) are the three isolates recorded from western Canada. Two segments (nt 453-674 and nt 1197-1503) from VP2 coding region of RNA of the isolates were amplified by polymerase chain reaction (PCR) for differentiation. Primers for cDNA synthesis and amplification by PCR were chosen from VP2 coding region of RNA of Ja-IPNV. The segment of 453-674 could be amplified in all the three isolates at annealing temperature from 50 to 60 degrees C. However the segment nt 1197-1503 could be amplified only from Jasper and not from AC or LT-INV at primer annealing temperature ranging from 50 degrees-60 degrees C. PCR product could be obtained from the latter two isolates only at Primer annealing temperature of 45 degrees C. This difference in annealing temperature in PCR amplification between the isolates could be used for differentiating the isolates at genome level.

Chemical and genetic characterization of bacteriocins produced by Carnobacterium piscicola LV17B.

Carnobacteriocins BM1 and B2 are thermostable class II bacteriocins produced by Carnobacterium piscicola LV17B. These bacteriocins were purified by a three-step procedure that included hydrophobic interaction, size exclusion, and reversed-phase high performance liquid chromatography. The purified peptides and fragments derived by enzymatic digestion were analyzed by Edman degradation, amino acid analysis, and mass spectrometry. An oxidized form of carnobacteriocin BM1 (carnobacteriocin B1) was also purified and characterized. Probes synthesized using information from the N-terminal amino acid sequences for the purified bacteriocins were used to locate structural genes for the carnobacteriocins. A 1.9-kilobase (kb) HindIII fragment from a 61-kb plasmid (pCP40) containing the carnobacteriocin B2 structural gene and a 4.0-kb EcoRI-PstI genomic fragment containing the carnobacteriocin BM1 structural gene were cloned and fully or partially sequenced, respectively. Expression of the chromosomal bacteriocin and its immunity function requires the presence of the 61-kb plasmid. The results indicate that both bacteriocins are synthesized as prebacteriocins. Post-translational cleavage of an 18-amino acid N-terminal extension at a Gly-Gly (positions -2 and -1) site takes place in each prepeptide to yield the mature 43-amino acid carnobacteriocin BM1 (molecular mass 4524.6) and the mature 48-amino acid carnobacteriocin B2 (molecular mass 4969.9). These two peptides showed significant amino acid homology to each other and with those class II bacteriocins which contain the YGNGV amino acid motif near the N terminus.

Characteristics and genetic determinant of a hydrophobic peptide bacteriocin, carnobacteriocin A, produced by Carnobacterium piscicola LV17A.

Carnobacteriocin A is a hydrophobic nonlantibiotic bacteriocin that is detected early in the growth cycle of Carnobacterium piscicola LV17A and encoded by a 49 MDa plasmid. The bacteriocin was purified using hydrophobic interaction and gel filtration chromatography, and reversed-phase HPLC. Three different active peaks (A1, A2 and A3) were detected, but the purified samples had identical N-terminal amino acid sequences for the first 15 amino acids as determined by Edman degradation analysis. Only a 2.4 kb fragment of the EcoRI digest of the plasmid pCP49 hybridized with a 23-mer oligonucleotide probe derived from amino acids 5 to 13 of the amino acid sequence. The structural gene for carnobacteriocin A is located 600 base pairs into the 2.4 kb EcoRI fragment, but no other genetic information was detected on this unit. The structural gene includes an 18 amino acid N-terminal extension of the bacteriocin, ending with Gly-Gly residues in the -2, -1 positions with respect to the cleavage site. The bacteriocin consists of 53 amino acids that differ markedly from the majority of hydrophobic peptide bacteriocins characterized to date. Based on the amino acid sequence derived from the nucleotide sequence a molecular mass of 5052.85 Da was calculated. Mass spectrometric analysis showed that the molecular mass of the major component (A3) was 2 Da lower, thereby indicating the presence of a disulphide bridge between Cys 22 and Cys 51. Carnobacteriocin A2 has a similar structure except that Met 52 is oxidized to a sulphoxide, whereas A1 appears to be a mixture of peptides derived proteolytically from A3 or A2.

The functional analysis of nonsense suppressors derived from in vitro engineered Saccharomyces cerevisiae tRNA(Trp) genes.

Nonsense suppressors derived from Saccharomyces cerevisiae tRNA(Trp) genes have not been identified by classical genetic screens, although one can construct efficient amber (am) suppressors from them by making the appropriate anticodon mutation in vitro. Herein, a series of in vitro constructed putative suppressor genes was produced to test if pre-tRNA(Trp) processing difficulties could help to explain the lack of classical tRNA(Trp)-based suppressors. It is clear that inefficient processing of introns from precursor tRNA(Trp), or inaccurate overall processing, may explain why some of these constructs fail to promote nonsense suppression in vivo. However, deficient processing must be only one of the reasons why classical tRNA(Trp)-based suppressors have not been characterized, as suppression may still be extremely weak or absent in instances where the in vitro construct can lead to an accumulation of mature tRNA(Trp). Furthermore, suppression is also very weak in strains transformed with an intronless derivative of a putative tRNA(Trp) ochre (oc) suppressor gene, wherein intron removal cannot pose a problem.

beta-Lactamase of Lysobacter enzymogenes: cloning, characterization and expression of the gene and comparison of the enzyme to other lactamases.

The gene for the periplasmic beta-lactamase of Lysobacter enzymogenes was isolated as part of a 1017 bp EcoRI fragment and the nucleotide sequence of the gene was determined. It has a G+C content of 71.5% and encodes a 27 amino acid signal sequence and the mature beta-lactamase of 276 amino acids which has a mass of 29,146 Da. The enzyme appears to be unique to L. enzymogenes but its amino acid sequence shows a high degree of homology with the amino acid sequences of the lactamase from Citrobacter diversus and other Class A beta-lactamases. The beta-lactamase gene of L. enzymogenes was expressed in Escherichia coli using pUC118 as the vector. The production of active beta-lactamase was highest after the active growth phase of the expression host and reached levels which were about three times higher than those obtained with L. enzymogenes.

Nucleotide sequence of sweet clover necrotic mosaic dianthovirus RNA-1.

The complete nucleotide sequence of sweet clover necrotic mosaic dianthovirus (SCNMV) RNA-1 has been determined. RNA-1 consists of 3876 nucleotides in length, containing three large open reading frames (ORFs). The 5'-proximal, internal and 3'-terminal ORFs potentially encode 27-kDa, 57-kDa and 37-kDa proteins, respectively. The frameshift event between the C-terminus of the 27-kDa protein and extension of the N-terminus of the 57-kDa protein may result in the formation of a 88-kDa protein which is presumed to be a replicase. The 37-kDa coat protein ORF is located immediately downstream of the 57-kDa ORF. The same genome organization and high similarity (80-92%) of both the nucleotide sequences and the deduced amino acid sequences between red clover necrotic mosaic dianthovirus and SCNMV suggest that they originate from a common progenitor, but have divergent evolution later. Striking similarity was detected between the putative RNA-dependent RNA polymerase of SCNMV and that of the tombus-, carmo-, necro-, machlomo- and luteoviruses, supporting a proposal that they belong to the same virus supergroup although there is a relatively low degree of coat protein sequence similarity in these viruses.

The primary structure of branched-chain alpha-oxo acid dehydrogenase from Bacillus subtilis and its similarity to other alpha-oxo acid dehydrogenases.

The bfmB mutant of Bacillus subtilis requires branched short-chain carboxylic acids for growth because the organism is known to be defective in branched-chain alpha-oxo acid dehydrogenase. The DNA in the region of bfmB has now been cloned and sequenced, and the gene has been analyzed. The results show that there are three open reading frames in the area, each of which is preceded by a putative ribosome binding site, and the last of which is followed by a putative transcription termination site with inverted repeats. The amino acid sequences deduced by analysis of the reading frames are highly similar (with 32-49% identity) to the E1 alpha, El beta and E2 components of pyruvate, 2-oxoglutarate and branched-chain alpha-oxo acid dehydrogenases from different sources. The thiamin diphosphate binding, putative subunit interaction and phosphorylation sites of the E1 alpha of four reported branched-chain alpha-oxo acid dehydrogenases from different sources are very similar to those of the first open reading frame (E1 alpha) of bfmB. A similar result is also obtained with the lipoyl-binding site (lysine) and its domain of the E2 component of alpha-oxo acid dehydrogenases from different sources. The present data, along with the reported biochemical data, lead to the conclusion that bfmB encodes a branched-chain alpha-oxo acid dehydrogenase, which is composed of E1 alpha, E1 beta and E2 genes. This organization is identical to that of the 2-oxoglutarate dehydrogenase in B. subtilis.

Complete nucleotide sequence of a linear plasmid from Streptomyces clavuligerus and characterization of its RNA transcripts.

The complete nucleotide sequence of a small linear plasmid (pSCL1) from Streptomyces clavuligerus has been determined. This plasmid is 11,696 bp in length, has a 72% G+C content, and has approximately 900-bp inverted terminal repeat sequences. A comparison of the inverted terminal repeats of pSCL1 with those of a linear plasmid from S. rochei shows that the two terminal sequences have a high degree of similarity (approximately 70%). Several small inverted repeats found in the long terminal sequences of both plasmids are also conserved. An analysis of the sequence and codon preferences indicates that pSCL1 has seven or eight highly probable protein-coding open reading frames (ORFs). However, only two RNA species encoded by pSCL1 were detected in S. clavuligerus grown in liquid culture. The larger of these transcripts (900 nucleotides) corresponds to an ORF and is likely to be an mRNA for a protein similar to the KorA protein of pIJ101. The smaller transcript (460 nucleotides) does not correspond to any ORF; however, its 5' end is complementary to the 5' end of a predicted mRNA, suggesting that it may function as an antisense RNA. The larger of the two RNA species was present at a high level during the early stage of growth in liquid medium, and then its apparent rate of transcription decreased and remained at a lower level through the later stages; the level of the smaller RNA species remained relatively constant through all stages of growth.

Characterization of the tRNA(Trp) genes of Saccharomyces cerevisiae.

The purpose of this work was to examine the tRNA(Trp)-encoding genes (tRNA(Trp)) of Saccharomyces cerevisiae to gain insight as to why tRNA(Trp) amber suppressors, isolated by conventional genetic techniques, have not been reported. The results herein indicate that the haploid yeast genome contains six tRNA(Trp) genes which map to five or six chromosomes. Not only do the six genes have identical coding sequences but their introns are also identical. Gene replacement experiments indicate that five copies of tRNA(Trp) are sufficient for cell viability. Thus, mutation of one tRNA(Trp) gene to a suppressor in vivo, lowering the functional number of tRNA(Trp) genes, would not be expected to be lethal.

A comparative study of the RNA-2 nucleotide sequences of two sweet clover necrotic mosaic virus strains.

The nucleotide sequences of the RNA-2s of two strains of sweet clover necrotic mosaic virus (SCNMV-38 and -59) have been determined. The RNA-2s of SCNMV-38 and -59 consist of 1446 and 1449 nucleotides, respectively, and both contain one major open reading frame (ORF) which potentially can encode polypeptides of 326 amino acid residues (about 36.5K), designated SC38P2 and SC59P2, respectively. The nucleotide sequences of SCNMV-38 and -59 RNA-2s show 93.2% similarity, and the amino acid sequences of SC38P2 and SC59P2 are 91.7% identical, although the identical nucleotides and amino acids are not distributed uniformly in RNA-2 and the encoded proteins. Two highly conserved regions (from positions 23 to 221 and 297 to 326) and a relatively divergent region (from positions 222 to 296) are found in the P2 proteins of these strains. A similar pattern is apparent on comparison of the nucleotide and deduced amino acid sequences of RNA-2 of these SCNMV strains with those of the Australian and Czechoslovakian isolates of red clover necrotic mosaic virus.

Transcriptional analysis of the isopenicillin N synthase-encoding gene of Streptomyces clavuligerus.

The gene (pcbC) encoding isopenicillin N synthase of Streptomyces clavuligerus is separated from an upstream open reading frame (ORF) by a 31-bp intergenic region. Inspection of the sequence of this intergenic region did not identify a promoter sequence. The promoter probe plasmid, pIJ4083, which contains the promoter-less catechol-2,3-dioxygenase (C23O)-encoding gene (xylE) as a reporter gene, was used to analyze the sequence upstream from the pcbC gene for promoter activity. Introduction of an SphI site at the start codon of pcbC by site-directed mutagenesis allowed the cloning of a 335-bp fragment (-334 to +1 in relation to the pcbC start codon) immediately upstream from xylE in pIJ4083. C23O activity was detected in both Streptomyces lividans and S. clavuligerus cultures that contained the upstream fragment, suggesting the presence of a promoter sequence. Northern analysis of total RNA extracted from S. clavuligerus identified a monocistronic 1.2-kb transcript hybridizing to a pcbC-specific probe. When RNA was isolated at various times during growth in liquid culture, the presence of a transcript was first detected during stationary phase. Analysis of the pcbC transcript by primer extension located the transcription start point to a C residue within the upstream ORF, 91 bp upstream from the pcbC start codon.

Characterization of leucocin A-UAL 187 and cloning of the bacteriocin gene from Leuconostoc gelidum.

Leucocin A-UAL 187 is a bacteriocin produced by Leuconostoc gelidum UAL 187, a lactic acid bacterium isolated from vacuum-packaged meat. The bacteriocin was purified by ammonium sulfate or acid (pH 2.5) precipitation, hydrophobic interaction chromatography, gel filtration, and reversed-phase high-performance liquid chromatography with a yield of 58% of the original activity. Leucocin A is stable at low pH and heat resistant, and the activity of the pure form is enhanced by the addition of bovine serum albumin. It is inactivated by a range of proteolytic enzymes. The molecular weight was determined by mass spectrometry to be 3,930.3 +/- 0.4. Leucocin A-UAL 187 contains 37 amino acids with a calculated molecular weight of 3,932.3. A mixed oligonucleotide (24-mer) homologous to the sequence of the already known N terminus of the bacteriocin hybridized to a 2.9-kb HpaII fragment of a 7.6-MDa plasmid from the producer strain. The fragment was cloned into pUC118 and then subcloned into a lactococcal shuttle vector, pNZ19. DNA sequencing revealed an operon consisting of a putative upstream promoter, a downstream terminator, and two open reading frames flanked by a putative upstream promoter and a downstream terminator. The first open reading frame downstream of the promoter contains 61 amino acids and is identified as the leucocin structural gene, consisting of a 37-amino-acid bacteriocin and a 24-residue N-terminal extension. No phenotypic expression of the bacteriocin was evident in several lactic acid bacteria that were electrotransformed with pNZ19 containing the 2.9-kb cloned fragment of the leucocin A plasmid.

Nucleotide sequence and characterization of the gene for secreted alkaline phosphatase from Lysobacter enzymogenes.

Lysobacter enzymogenes produces an alkaline phosphatase which is secreted into the medium. The gene for the enzyme (phoA) was isolated from a recombinant lambda library. It was identified within a 4.4-kb EcoRI-BamH1 fragment, and its sequence was determined by the chain termination method. The structural gene consists of an open reading frame which encodes a 539-amino-acid protein with a 29-residue signal sequence, followed by a 119-residue propeptide, the 281-residue mature phosphatase, and a 110-residue carboxy-terminal domain. The roles of the propeptide and the carboxy-terminal peptide remain to be determined. A molecular weight of 30,000 was determined for the mature enzyme from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino acid sequence was compared with sequences available in the current protein data base, and a region of the sequence was found to show considerable homology with sequences in mammalian type 5 iron-containing purple acid phosphatases.

Isolation and molecular characterization of the ribosomal protein L6 homolog from Chlamydia trachomatis.

The cloning of a Chlamydia trachomatis eukaryotic cell-binding protein reported earlier from our laboratory (R. Kaul, K. L. Roy, and W. M. Wenman, J. Bacteriol. 169:5152-5156, 1987) represents an artifact generated by nonspecific recombination of chromosomal DNA fragments. However, the amino terminus of this plasmid-encoded fusion product demonstrated significant homology to Escherichia coli ribosomal protein L6. By using a 458-bp PstI-HindIII fragment of recombinant pCT161/18 (representing the 5' end of the cloned gene), we isolated and characterized a C. trachomatis homolog of the ribosomal protein L6 gene of E. coli. Sequence analysis of an 1,194-bp EcoRI-SacI fragment that encodes chlamydial L6 (designated CtaL6e) revealed a 552-bp open reading frame comprising 183 amino acids and encodes a protein with a molecular weight of 19,839. Interestingly, complete gene homology between C. trachomatis serovars L2 and J, each of which exists as a single copy per genome, was observed. Expression of a plasmid-encoded gene product is dependent on the lac promoter, since no product was obtained if the open reading frame was oriented in opposition to the lac promoter. Immunoblotting of purified ribosomes revealed functional, as well as antigenic, homology between the E. coli and C. trachomatis ribosomal L6 proteins.