Genome-wide analysis of the L-methionine biosynthetic pathway in Corynebacterium glutamicum by targeted gene deletion and homologous complementation

The genome sequence of Corynebacterium glutamicum, a gram-positive soil bacterium widely used as an amino acid producer, was analyzed by a similarity-based approach to elucidate the pathway for the biosynthesis of L-methionine. The functions of candidate ORFs were derived by gene deletion and, if necessary, by homologous complementation of suitable mutants. Of nine candidate ORFs (four of which were known previously), seven ORFs (cg0754 (metX), cg0755 (metY), cg1290 (metE), cg1702 (metH), cg2383 (metF), cg2536 (aecD), and cg2687 (metB)) were demonstrated to be part of the pathway while two others (cg0961 and cg3086) could be excluded. C. glutamicum synthesizes methionine in three, respectively four steps, starting from homoserine. C. glutamicum possesses two genes with similarity to homoserine acetyltransferases but only MetX can act as such while Cg0961 catalyzes a different, unknown reaction. For the incorporation of the sulfur moiety, the known functions of MetY and MetB could be confirmed and AecD was proven to be the only functional cystathionine beta-lyase in C. glutamicum, while Cg3086 can act neither as cystathionine gamma-synthase nor as cystathionine beta-lyase. Finally, MetE and MetH, which catalyze the conversion of L-homocysteine to L-methionine, could be newly identified, together with MetF which provides the necessary N(5)-methyltetrahydrofolate.

Self-reported efficacy of an all in-the-ear-canal prosthetic device to inhibit stuttering during one hundred hours of university teaching: an autobiographical clinical commentary

This manuscript outlines the lifelong battle with severe stuttering and describes a new modality of effective amelioration of the disorder from the standpoint of a university professor and researcher in the field of stuttering. Childhood reactions to stuttering are discussed, along with the educational and vocational impact of stuttering. Ongoing therapy was received throughout the formative years and into adulthood, emphasizing reduced rates of speech. The use of Delayed Auditory Feedback (DAF) was found to induce fluent speech, but was considered only as a tool for decreasing the speech rate to achieve fluency. When fluency under DAF was discovered to be possible at faster speech rates, the possibility that the use of DAF and other forms of altered auditory feedback could themselves have an inhibitory effect on stuttering, without concomitant rate reduction was investigated. An In-The-Canal (ITC) fluency-enhancing device was used that provided DAF and Frequency Altered Feedback (FAF) to produce more fluent speech. After 10 months of use, the author was relatively free from stuttering. Speech was natural sounding, relatively spontaneous and unlaboured with an absence of fear. However, further testing (that is currently underway at various centres) is necessary before generalizations can be made.

The end-product of behavioural stuttering therapy: three decades of denaturing the disorder

ISSUE

The state of stuttering therapy continues to be of great concern in the field of speech-language pathology. Despite decades of research and clinical practical, stuttering is still treated by ineffective and inefficient means.

PROPOSAL

Our research group suggests that therapy failures stem from the use behavioural approaches; procedures that have resulted in only temporary and unnatural alleviation from the symptomatology by masking the disorder. These procedures 'denature' the disorder and induce pseudofluency rather than true fluency. It is proposed that in order to truly provide relief to those who stutter, professionals need to view both the overt and covert components of the disorder from the standpoint of attaining true fluency. Only then can the true syndrome-like nature of stuttering be addressed. In order to achieve true fluency the use of stuttering inhibitors must be incorporated such as choral speech and its permutations to derive natural sounding, stable and effortless speech in those who stutter.

CONCLUSION

By doing so, the goal is to not only derive stable and natural-sounding speech, but also to help remove such factors as the expectancy, anticipation and the fear of stuttering that generally continue to shackle most people who stutter following behavioural therapy.

A common element in the immediate inducement of effortless, natural-sounding, fluent speech in people who stutter: 'the second speech signal'

Recent attempts to find a common element in the inducement of fluent speech have focused on Wingate's notion that fluency can be induced via an altered manner of speaking by placing an emphasis on phonation. The problem with this notion of fluency enhancement is that it appears to be too expansive a scheme of fluency. The schemata allows for any forward flowing speech or speech-like act to be considered fluent despite the increased cognitive mediation, the extra effort involved in implementing the procedure, the unnaturalness of the resultant end product, and a lack of stability over time. It is proposed that the only significant characteristics of 'true fluency' are that it is indistinguishable from the typical fluent speech of people who do not stutter, and that it is effortless in nature. This is achieved via the use of a second speech signal which is not cognitive in nature, is operationally delineated, and is easy to manipulate.

Reduction of stuttering: the dual inhibition hypothesis

Treatment for stuttering attempts to reduce or eliminate the observable core markers of the disorder, specifically repetitions and prolongation. In this hypothesis, it is proposed that stuttering may be inhibited by two distinct yet related procedures: active inhibition and passive inhibition. Active inhibition is brought about when the person who stutters makes volitional changes to his or her speaking pattern, such as when employing behavioral modification techniques. Passive inhibition automatically inhibits the involuntary stuttering block and can be induced from an external source, such as altered auditory feedback, or by the use of sufficient active inhibition. It is suggested that passively inhibiting stuttering results in speech that is more automatic, natural sounding, and truly fluent speech than the speech that is derived primarily from active inhibition. Evidence of passive inhibition resulting from active inhibition can be seen when people who stutter exhibit uncontrolled fluency following behavioral therapy.

Relaxed rrn expression and amino acid requirement of a Corynebacterium glutamicum rel mutant defective in (p)ppGpp metabolism

The stringent response in Corynebacterium glutamicum was investigated. Sets of rrn-cat fusions were constructed in their native chromosomal position to examine the effects of amino acid starvation in a rel(+) strain and a Deltarel mutant defective in (p)ppGpp metabolism. The expression of the six rrn operons in the rel(+) control was stringently regulated and reduced to 79% upon induction of amino acid starvation. The Deltarel mutant displayed a relaxed regulation and was unable to reduce the rrn expression under amino acid depletion conditions. In addition, the Deltarel mutant grew more slowly in minimal medium than a rel(+) control. This growth effect was restored by a plasmid-encoded copy of rel or, alternatively, by supplementation of the minimal medium with the amino acid mixture casamino acids. In particular, the Deltarel strain of C. glutamicum displayed a requirement for the amino acids histidine and serine.

Producing the vowel/a/ prior to speaking inhibits stuttering in adults in the English language

This study investigated the effects of producing and listening to the vowel /a/ on the frequency of overt stuttering moments in eight people who stuttered. Stuttering frequency counts were made for the speech produced in the control condition, and after each of these four experimental conditions: (a) producing a vowel /a/ for 4 s; (b) producing a vowel /a/ for 4 s and waiting for 4 s; (c) listening to a recording of the vowel /a/ for 4 s; and (d) listening to a recording of the vowel /a/ for 4 s and waiting for 4 s. A significant reduction in the stuttering frequency was only observed following production of the vowel /a/ without a 4 s delay (P=0.02), suggesting that the vowel production prior to speech, serves as a temporary fluency enhancer. Its similarity to the occurrence of overt stuttering moments (e.g. discrete part-word repetitions and prolongation's) and its relationship to the fundamental nature of the pathology are discussed.

Proteome analysis of Corynebacterium glutamicum

By the use of different Corynebacterium glutamicum strains more than 1.4 million tons of amino acids, mainly L-glutamate and L-lysine, are produced per year. A project was started recently to elucidate the complete DNA sequence of this bacterium. In this communication we describe an approach to analyze the C. glutamicum proteome, based on this genetic information, by a combination of two-dimensional (2-D) gel electrophoresis and protein identification via microsequencing or mass spectrometry. We used these techniques to resolve proteins of C. glutamicum with the aim to establish 2-D protein maps as a tool for basic microbiology and for strain improvement. In order to analyze the C. glutamicum proteome, methods were established to fractionate the C. glutamicum proteins according to functional entities, i.e., cytoplasm, membranes, and cell wall. Protein spots of the cytoplasmic and membrane fraction were identified by N-terminal sequencing, immunodetection, matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) and electrospray ionization-mass spectrometry (ESI-MS). Additionally, a protocol to analyze proteins secreted by C. glutamicum was established. Approximately 40 protein spots were observed on silver-stained 2-D gels, 12 of which were identified.

TetZ, a new tetracycline resistance determinant discovered in gram-positive bacteria, shows high homology to gram-negative regulated efflux systems

The complete nucleotide sequence of the tetracycline resistance plasmid pAG1 from the gram-positive soil bacterium Corynebacterium glutamicum 22243 (formerly Corynebacterium melassecola 22243) was determined. The R-plasmid has a size of 19,751 bp and contains at least 18 complete open reading frames. The resistance determinant of pAG1 revealed homology to gram-negative tetracycline efflux and repressor systems of Tet classes A through J. The highest levels of amino acid sequence similarity were observed to the transmembrane tetracycline efflux protein TetA(A) and to the tetracycline repressor TetR(A) of transposon Tn1721 with 64 and 56% similarity, respectively. This is the first time a repressor-regulated tet gene has been found in gram-positive bacteria. A new class of tetracycline resistance and repressor proteins, termed TetA(Z) and TetR(Z), is proposed.

Stutter-free and stutter-filled speech signals and their role in stuttering amelioration for English speaking adults

This study examined the power of an exogenously generated stuttered speech signal on stuttering frequency when compared to an exogenously generated normal speech signal. In addition, we examined the specific components of the second speech signal, which might be responsible for the inducement of fluency in people who stutter. Eight males and two females who stuttered participated in this study. Experiment I involved meaningful speech: normal continuous speech, normal interrupted speech, stuttered continuous speech, and stuttered interrupted speech, whereas Experiment II involved vowels and consonants: /a/, /a-i-u/, /s/, /s-sh-f/. The results indicated that stuttered and normal speech signals were equally effective in reducing stuttering frequency. Further, the vowels were more powerful than consonants in inducing fluency for people who stutter. It is suggested that acoustic manifestations of stuttering, rather than a problem, may be a natural compensatory mechanism to bypass or inhibit the 'involuntary block' at the neural level.

Inducement of fluent speech in persons who stutter via visual choral speech

A novel phenomenon of fluency enhancement via visual gestures of speech in the absence of traditional auditory feedback is reported herein. The effect on visual choral speech on stuttering frequency was investigated. Ten participants who stuttered recited memorized text aloud under two conditions. In a visual choral speech (VCS) condition participants were instructed to focus their gaze on the face, lips and jaw of a research assistant who 'silently mouthed' the text in unison. In a control condition, participants recited memorized text to the research assistant who sat motionless. A statistically significant (P=0.0025) reduction of approximately 80% in stuttering frequency was observed in the VCS condition. As visual linguistic cues are sufficient to activate the auditory cortex, one may speculate that VCS induces fluency in a similar yet undetermined manner as altered auditory feedback does.

The 51,409-bp R-plasmid pTP10 from the multiresistant clinical isolate Corynebacterium striatum M82B is composed of DNA segments initially identified in soil bacteria and in plant, animal, and human pathogens

The 51,409-bp DNA sequence of the multiresistance plasmid pTP10 from the gram-positive opportunistic human pathogen Corynebacterium striatum M82B has been determined. Fully automated genome interpretation led to the identification of 47 ORFs. Analysis of the genetic organization of pTP10 suggests that the plasmid is composed of eight DNA segments, the boundaries of which are represented by transposons and insertion sequences. The DNA segments of pTP10 are highly similar to (1) a plasmid-encoded erythromycin resistance region from the human pathogen Corynebacterium diphtheriae; (2) a chromosomal DNA region from Mycobacterium tuberculosis; (3) a plasmid-encoded chloramphenicol resistance region from the soil bacterium Corynebacterium glutamicum; (4) transposable elements from phytopathogenic gram-negative Pseudomonas, Xanthomonas and Erwinia species; and (5) a plasmid-encoded aminoglycoside resistance region from the gram-negative fish pathogen Pasteurella piscicida. The complete DNA sequence of pTP10 provides genetic information regarding the mechanisms of resistance to 16 antimicrobial agents that belong to six structural classes. In addition, the mosaic structure of pTP10 represents the evolutionary consolidation into a single plasmid molecule of antimicrobial resistances from microorganisms found in different habitats by means of mobile elements, resulting in the generation of a multiresistant bacterium that can infect humans.

Effects of monitoring condition and frequency-altered feedback on stuttering frequency

The purpose of the study was to examine stuttering frequency during speaking conditions that are believed to mitigate stuttering frequency both with normal nonaltered auditory feedback (NAF) and a known fluency-enhancing feedback. Specifically, stuttering frequency was examined as a function of three monitoring conditions under NAF and frequency-altered feedback (FAF): no monitoring (i.e., speaking alone, in the absence of audio and visual recording), audiovisual monitoring (i.e., speaking alone with audiovisual recording), and audiovisual monitoring with observers (i.e., speaking with audiovisual recording in the presence of two observers). Seven adults and one adolescent who stutter served as participants. Stuttering frequency was differentially affected across monitoring conditions under each auditory feedback condition (p = .027). Post hoc analyses revealed no significant difference in stuttering frequency between the two conditions in the absence of the observers (i.e., no monitoring vs. audiovisual monitoring) under NAF (p = .45). There was, however, a significant difference in stuttering frequency for the no-monitoring and audiovisual-monitoring conditions relative to the audiovisual-monitoring-with-observers condition (p = .0002). There was no statistically significant difference in stuttering frequency across monitoring conditions under FAF (p > .05). The findings are consistent with the notion that during NAF stuttering frequency varies as a function of hierarchical socio-environmental conditions in which inanimate monitoring conditions constitute one entity. Such a relationship does not exist during FAF.

Pantothenate production in Escherichia coli K12 by enhanced expression of the panE gene encoding ketopantoate reductase

Using gene replacement and transposon Tn5 mutagenesis, an Escherichia coli ilvC panE double mutant completely lacking ketopantoate reductase activity was isolated. This E. coli double mutant was employed to isolate the E. coli panE gene by genetic complementation. The E. coli panE gene is characterized by a 912 bp coding region, which specifies a protein of 303 amino acids with a deduced molecular mass of 33.8 kD. A panE expression plasmid carrying the panE gene under the control of the tac promotor was constructed. Introduction of the panE expression plasmid into E. coli resulted in a threefold increase in ketopantoate reductase activity. It was also shown that the enhanced panE expression in E. coli K12 led to 3.5-fold increase in pantothenate excretion. Pantothenate excretion could even be more enhanced when the growth medium was supplemented with ketopantoate.

The Corynebacterium glutamicum insertion sequence ISCg2 prefers conserved target sequences located adjacent to genes involved in aspartate and glutamate metabolism

An IS element, termed ISCg2, was identified in the chromosome of Corynebacterium glutamicum ATCC 13032. After screening a cosmid library of the C. glutamicum ATCC 13032 genome, six copies of ISCg2 including their flanking regions were sequenced and analyzed. ISCg2 is 1636 bp in length and has 26-bp imperfect inverted repeats flanked by 3-bp direct repeats. By comparisons with other IS elements, ISCg2 was classified as a member of the IS30 family of insertion sequences. The six copies of ISCg2 were identical at the nucleotide level and were located in intergenic, AT-rich regions of the chromosome. The regions in which the six copies of ISCg2 were inserted displayed significant similarities. This similarity extends over a region of 65 bp, which was assumed to be the target region for ISCg2. Interestingly, five of the six copies of ISCg2 were located adjacent to genes that may be involved in aspartate and glutamate metabolism or its regulation. Investigation of the distribution of ISCg2 showed that the IS element is restricted to certain C. glutamicum strains. Analysis of various integration regions indicates active transposition of ISCg2 in C. glutamicum.

Expression of the Corynebacterium glutamicum panD gene encoding L-aspartate-alpha-decarboxylase leads to pantothenate overproduction in Escherichia coli

The Corynebacterium glutamicum panD gene was identified by functional complementation of an Escherichia coli panD mutant strain. Sequence analysis revealed that the coding region of panD comprises 411 bp and specifies a protein of 136 amino acid residues with a deduced molecular mass of 14.1 kDa. A defined C. glutamicum panD mutant completely lacked L-aspartate-alpha-decarboxylase activity and exhibited beta-alanine auxotrophy. The C. glutamicum panD (panDC. g.) as well as the E. coli panD (panDE.c.) genes were cloned into a bifunctional expression plasmid to allow gene analysis in C. glutamicum as well as in E. coli. The enhanced expression of panDC.g. in C. glutamicum resulted in the formation of two distinct proteins in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, leading to the assumption that the panDC.g. gene product is proteolytically processed into two subunits. By increased expression of panDC.g. in C. glutamicum, the activity of L-aspartate-alpha-decarboxylase was 288-fold increased, whereas the panDE.c. gene resulted only in a 4-fold enhancement. The similar experiment performed in E. coli revealed that panDC.g. achieved a 41-fold increase and that panDE.c. achieved a 3-fold increase of enzyme activity. The effect of the panDC.g. and panDE.c. gene expression in E. coli was studied with a view to pantothenate accumulation. Only by expression of the panDC.g. gene was sufficient beta-alanine produced to abolish its limiting effect on pantothenate production. In cultures expressing the panDE.c. gene, the maximal pantothenate production was still dependent on external beta-alanine supplementation. The enhanced expression of panDC.g. in E. coli yielded the highest amount of pantothenate in the culture medium, with a specific productivity of 140 ng of pantothenate mg (dry weight)-1 h-1.

The tetAB genes of the Corynebacterium striatum R-plasmid pTP10 encode an ABC transporter and confer tetracycline, oxytetracycline and oxacillin resistance in Corynebacterium glutamicum

The tetracycline resistance region of the 50-kb R-plasmid pTP10 from the clinical isolate Corynebacterium striatum M82B was analyzed in Corynebacterium glutamicum ATCC 13032 and confined to a 4.4-kb SphI-Sa/I DNA fragment. Nucleotide sequence analysis revealed two open reading frames, termed tetA and tetB, specifying proteins of 513 and 528 amino acids, respectively. The deduced amino acid sequences of tetAB displayed similarity to ATP-binding cassette transporters including StrV and StrW of Streptomyces glaucescens which are proposed to play a role in the export of streptomycin-like aminoglycosides. An antibiotic susceptibility screening in C. glutamicum showed that the tetAB genes confer resistance to tetracycline, oxytetracycline and to the structurally and functionally unrelated beta-lactam antibiotic oxacillin.

A latent trait approach to the development of persistent stuttering

The premise that stuttering disorders develop according to the orthogenetic principle, preceding in a continuous, unilinear fashion from a state of relative lack of differentiation to a state of increasing differentiation and hierarchic integration, was examined. Responses to Woolf's Perceptions of Stuttering Inventory of 87 individuals who stutter were analyzed using a Rasch 1980 latent trait model for dichotomously scored data. Analyses of responses indicated struggle, avoidance, and expectation through the development of stuttering that became increasingly articulated, integrated, stable, and yet responsive to environmental changes. Four stages of development were noted: Stage I was characterized by the expectation of interruptions in the flow of speech, the addition of unnecessary sounds, and general body tension. Stage II was typified by distinctions between troublesome and not so troublesome words and sounds and between the speaker and various audiences and contexts for speaking. In Stage III, speech control decreased despite more focused and complex efforts to control the environment and the speech apparatus. Stage IV was characterized by automatic scanning of all speech, increasingly uncontrolled body movements, and attempts to produce fluent speech by way of comprehensive changes to sound, rhythm, and pitch. Follow-up of 29 respondents suggested the latent struggle was generally stable over time.

Quantitative electroencephalogram of posterior cortical areas of fluent and stuttering participants during reading with normal and altered auditory feedback

In the left and right hemisphere, posterior quantitative electroencephalogram Beta band activity (13.5-25.5 Hz) of seven adult participants who stutter and seven age-matched normal controls was obtained while subjects read text under three experimental conditions of normal auditory feedback, delayed auditory feedback, and frequency-altered feedback. Data were obtained from surface electrodes affixed to the scalp using a commercial electrode cap. Electroencephalogram activity was amplified, band-pass analog-filtered, and then digitized. During nonaltered auditory feedback, stuttering participants displayed Beta band hyperreactivity, with the right temporal-parietal lobe region showing the greatest activity. Under conditions of delayed auditory feedback and frequency-altered auditory feedback, the stuttering participants displayed a decrease in stuttering behavior accompanied by a strong reduction in Beta activity for the posterior-temporal-parietal electrode sites, and the left hemisphere posterior sites evidenced a larger area of reactivity. Such findings suggest than an alteration in the electrical fields of the cortex occurred in the stuttering participants under both conditions, possibly reflecting changes in neurogenerator status or current dipole activity. Further, one could propose that stuttering reflects an anomaly of the sensory-linguistic motor integration wherein each hemisphere generates competing linguistic messages at hyperreactive amplitudes.

Corynebacterium striatum chloramphenicol resistance transposon Tn5564: genetic organization and transposition in Corynebacterium glutamicum

The clinical isolate Corynebacterium striatum M82B (formerly Corynebacterium xerosis M82B) carries the 50-kb R-plasmid pTP10 conferring resistance to the antibiotics chloramphenicol, erythromycin, kanamycin, and tetracycline. DNA sequence analysis of the chloramphenicol resistance region revealed the presence of the 4155-bp transposable element Tn5564. The ends of Tn5564 are identical 22-bp inverted repeats flanked by a 6-bp target site duplication. The central region of Tn5564 encodes the chloramphenicol resistance gene cmx, specifying a transmembrane chloramphenicol efflux protein, and an open reading frame homologous to transposases of insertion sequences identified in Arthrobacter nicotinovorans and Bordetella pertussis. Furthermore, the 1715-bp insertion sequence IS1513 encoding a putative transposase of the IS30 family is an integral part of Tn5564 and is located upstream of cmx. For transposon mutagenesis, Tn5564 was transferred to Corynebacterium glutamicum on a mobilizable Escherichia coli plasmid using RP4-mediated intergeneric conjugation. Transposition of Tn5564 in C. glutamicum occurred with a frequency of 3.3 x 10(-8) and resulted in an insertion into target sites containing the central palindromic tetranucleotide CTAG. A Tn5564-induced mutant strain of C. glutamicum was found to carry the transposon in the ftsZ gene region.

Mice lacking the type I interleukin-1 receptor do not lose bone mass after ovariectomy

We measured the effects of ovariectomy on the bone mass of mice that lacked type I interleukin-1 receptor (IL-I R1 -/- mice) in two genetic backgrounds (C57BL/6 x 129/Sv and C57BL/6) to investigate the role of interleukin-1 in the actions of estrogen on bone. At three weeks after surgery, ovariectomized wild-type mice decreased trabecular bone volume in the proximal humerus by 70% in a C57BL/6 x 129/Sv background and 48% in a C57BL/6 background compared to sham-operated controls. In contrast, there was no significant decrease in trabecular bone mass in IL-1 R1 -/- mice after ovariectomy. The estrogen status of all groups was confirmed by measurement of uterine wet weight. These results demonstrate that a functional IL-1 response pathway is required for mice to lose trabecular bone mass after ovariectomy in this model and they imply that IL-1 is an important mediator of the effects of ovariectomy on bone mass. Hence, therapeutic interventions that block the effects of IL-1 on bone may be beneficial for treating diseases of rapid bone loss such as post-menopausal osteoporosis.

Isoleucine uptake in Corynebacterium glutamicum ATCC 13032 is directed by the brnQ gene product

By complementation analysis of an isoleucine-uptake-deficient Escherichia coli strain, it was shown that a 1.6-kb HindIII-StuI fragment of Corynebacterium glutamicum ATCC 13032, located downstream of the aecD gene, encodes an isoleucine uptake system. Sequence analysis revealed that the complementing fragment carried an open reading frame, termed brnQ, that encodes a protein with sequence similarities to branched-chain amino acid carriers of gram-positive and gram-negative bacteria. The brnQ gene specifies a predominantly hydrophobic protein of 426 amino acid residues with a calculated molecular mass of 44.9 kDa. A topology prediction by neural network computer analysis suggests the existence of 12 hydrophobic segments that most probably form transmembrane alpha-helices. A C. glutamicum mutant strain harboring a defined deletion of brnQ in the chromosome showed a considerably lower isoleucine uptake rate of 0.04 nmol min-1 mg (dry mass)-1 as compared to the wild-type strain rate of 1.2 nmol min-1 mg (dry mass)-1. Overexpression of brnQ by means of a tac promotor resulted in an elevated uptake rate for isoleucine of 11.3 nmol min-1 mg (dry mass)-1. Evidently, the brnQ gene encodes the only transport system in C. glutamicum directing isoleucine uptake.

The Corynebacterium glutamicum cglIM gene encoding a 5-cytosine methyltransferase enzyme confers a specific DNA methylation pattern in an McrBC-deficient Escherichia coli strain

The cglIM gene of the coryneform soil bacterium Corynebacterium glutamicum ATCC 13032 has been cloned and characterized. The coding region comprises 1092 nucleotides and specifies a protein of 363 amino acid residues with a deduced Mr of 40700. The amino acid sequence showed striking similarities to methyltransferase enzymes generating 5-methylcytosine residues, especially to M x NgoVII from Neisseria gonorrhoeae recognizing the sequence GCSGC. The cglIM gene is organized in an unusual operon which contains, in addition, two genes encoding stress-sensitive restriction enzymes. Using PCR techniques the entire gene including the promoter region was amplified from the wild-type chromosome and cloned in Escherichia coli. Expression of the cglIM gene in E. coli under the control of its own promoter conferred the C. glutamicum-specific methylation pattern to co-resident shuttle plasmids and led to a 260-fold increase in the transformation rate of C. glutamicum. In addition, the methylation pattern produced by this methyltransferase enzyme is responsible for the sensitivity of DNA from C. glutamicum to the modified cytosine restriction (Mcr) system of E. coli.

Effect of altered auditory feedback on people who stutter during scripted telephone conversations

The effect of altered auditory feedback (AAF) conditions on stuttering during scripted telephone conversations was investigated. Nine adult participants made 15 scripted telephone calls to business in New York City. Alterations in the participants' auditory feedback signal were generated by a commercially available digital signal processor (Casa Futura Technologies Desktop Fluency System Model BTD-400) that shifted participants' speech one-half octave down in frequency, produced a 50-ms delay, or produced non-altered auditory feedback. The AAF effects produced by the digital signal processor were not perceived by the recipients of the telephone calls. The proportion of stuttering events per scripted telephone conversations were significantly reduced in the AAF conditions relative to the non-altered auditory feedback condition (p = .0004). Stuttering frequency was reduced by 55% and 60% for the FAF and DAF, respectively. These findings demonstrate the applicability of this technology to situations of daily living involving telephone use.

Effect of speaking into a passive resonator on stuttering frequency

The effect on stuttering frequency of speaking into a passive resonator was investigated. Eight participants who stuttered read aloud with and without the benefit of the resonator. A statistically significant reduction of approximately 30% in stuttering frequency was observed while the participants spoke with the resonator. These and similar commercially available devices may be employed with individuals who stutter, particularly children, as a means of enhancing fluency.

Effect of monaural and binaural altered auditory feedback on stuttering frequency

The effect of monaural and binaural alterations in auditory feedback on stuttering frequency was investigated. Eleven participants who stutter read aloud under nonaltered auditory feedback (NAF) and monaural and binaural conditions of frequency altered feedback [(FAF), on-quarter octave shift upward] and delayed auditory feedback [(DAF), 50-ms delay] at a normal speech rate. Relative to the NAF condition, reductions in stuttering frequency of approximately 60%-75% were found with the altered auditory feedback conditions. Post hoc single-df comparisons revealed a reduction in stuttering frequency with altered auditory feedback versus NAF (p < 0.0001), a greater reduction in stuttering frequency for binaural compared to monaural altered auditory feedback (p = 0.028), and nonsignificant differences in stuttering frequencies for right versus left monaural conditions (p = 0.54) and DAF versus FAF (p = 0.70).

A Corynebacterium glutamicum gene conferring multidrug resistance in the heterologous host Escherichia coli

A chromosomal DNA fragment from the erythromycin-sensitive bacterium Corynebacterium glutamicum ATCC 13032 was shown to mediate resistance against erythromycin, tetracycline, puromycin, and bleomycin in Escherichia coli. Multicopy cloning of the fragment did not cause a resistance phenotype in C. glutamicum. The corresponding gene encodes a hydrophobic protein with 12 potential transmembrane-spanning ex-helical segments showing similarity to drug-H+ antiporters.

Effect of frequency altered feedback and audience size on stuttering

The effect of frequency altered feedback (FAF) and audience size on stuttering frequency was examined. Nine adults who stutter orally read to audiences of two, four and 15 people under conditions of FAF (one-half octave shift down) and non-altered auditory feedback (NAF). There was no statistically significant effect of audience size on stuttering frequency (p > 0.05). A statistically significant reduction in stuttering frequency was found under FAF relative to NAF (p < 0.5). Collapsed across audience conditions, stuttering frequency was reduced by 74%. These findings suggest that FAF may be useful as a treatment tool.

Formant frequency characteristics of elderly speakers in contextual speech

The present study measured F1 and F2 formant frequency levels of elderly and young male and female speakers producing the /i/, /ae/, [symbol: see text], /u/, and /a/ vowels in two carrier phrases. Results of a series of ANOVAs showed significant interactions of speaker age x vowel for both F1 and F2 formant frequencies for the male and female speakers. Results suggested that while elderly male speakers exhibit significant alterations in vowel production during contextual speech, elderly female speakers generally maintain formant frequency integrity or appropriate articulatory posturing during contextual vowel productions.

Construction of L-lysine-overproducing strains of Brevibacterium lactofermentum by targeted disruption of the hom and thrB genes

The mobilization of plasmids from gram-negative Escherichia coli to gram-positive Brevibacterium lactofermentum, mediated by P-type transfer functions, was used to construct disrupted mutants blocked specifically in the homoserine branch of the aspartate pathway. The mutant strain B. lactofermentum R31 showed an efficiency of conjugal transfer two to three orders of magnitude higher than that of the wild-type strain B. lactofermentum ATCC 13869. The hom- and thrB-disrupted mutants of B. lactofermentum ATCC 13869 were lysine overproducers. B. lactofermentum R31 mutants do not overproduce lysine because R31 is an alanine-overproducing strain and channels the pyruvate needed for lysine biosynthesis to the production of alanine.

Lack of evidence for an increase in interleukin-6 expression in adult murine bone, bone marrow, and marrow stromal cell cultures after ovariectomy

Interleukin-6 (IL-6) has been implicated as a mediator of postmenopausal bone loss. In vitro studies of bone and bone marrow cells have suggested that estrogen regulates bone turnover by controlling the production of IL-6, a potent stimulator of osteoclastogenesis and bone resorption. To investigate this hypothesis in an in vivo model, we examined the effect of ovariectomy or estrogen replacement on IL-6 mRNA and protein expression in adult mouse bone and bone marrow in vivo and in marrow stromal cell cultures. Eight-week-old CD-1 mice were sham-operated (SHAM), ovariectomized (OVX), or ovariectomized and subcutaneously implanted with 21-day slow-release pellets containing 10 micrograms of 17 beta-estradiol (O + E). Placebo pellets were implanted in the SHAM and OVX mice. Uterine weights at 1, 2, or 3 weeks after surgery were significantly decreased (68-76%) in OVX animals compared with SHAM or O + E. In mice sacrificed at 1 or 3 weeks after surgery, we found by nonquantitative reverse transcribed polymerase chain reaction (RT-PCR), that SHAM, OVX, and O + E calvariae (CALV) constitutively expressed IL-6 mRNA. In contrast, IL-6 mRNA was either barely detectable or absent in the tibia (TIB) and bone marrow (BM). In the mice sacrificed 3 weeks after surgery, we determined by quantitative RT-PCR that IL-6 mRNA in the CALV from the OVX and O + E groups were decreased by 81 and 92%, respectively, compared with SHAM. IL-6 protein levels in the flushed bone marrow (BMSups) were detectable and were not significantly different among the groups. In bone marrow cells that were cultured for 1 week, basal levels of IL-6 protein were low and did not differ significantly among the SHAM, OVX, or O + E groups sacrificed 1, 2, or 3 weeks after surgery. After the addition of hrIL-1 alpha, IL-6 protein levels increased 100- to 1300-fold over control. IL-6 levels in cells from animals sacrificed 2 weeks after surgery were significantly lower in the hrIL-1 alpha-stimulated OVX and O + E groups than in hrIL-1 alpha-stimulated SHAM cell cultures. In conclusion, in this model we could find no increase in IL-6 production with in vivo estrogen withdrawal in calvaria, long bones, bone marrow, or marrow stromal cell cultures. If increases in IL-6 expression are involved in the effects of estrogen withdrawal on bone, the magnitude of these changes are relatively small and below the limits of detection of the assays that we employed.

Interleukin-6 expression and histomorphometry of bones from mice deficient in receptors for interleukin-1 or tumor necrosis factor

We examined the roles of interleukin-1 Type I receptor (IL-1R1) and tumor necrosis factor receptor 1 (TNFR1) in bone metabolism using mice rendered deficient in these receptors by gene targeting. Sections of decalcified paraffin-embedded calvariae and humeri from 11- to 12-week-old mice deficient in IL-1 Type I receptor (IL-1R1-/-) or TNF receptor 1 (TNFR1-/-) were examined by histomorphometry. Wild-type mice (C57BL/6J x 129/J, WILD) served as controls. Interleukin-6 (IL-6) production in primary osteoblastic and bone marrow stromal cell cultures in response to parathyroid hormone (PTH, 100 ng/ml), IL-1 alpha (10 ng/ml), and TNF-alpha (10 ng/ml) was also examined. IL-1R1-/- and TNFR1-/- mice were viable and appeared phenotypically normal. However, the body weights of the IL-1R1-/- mice were 30% less than WILD, while the TNFR1-/- mice weighed 30% more than WILD mice of equivalent age. Calvariae and humeri of IL-1R1-/- and TNFR1-/- mice were normal with respect to trabecular bone volume, osteoclast number, osteoclast surface, growth plate widths, and cortical thickness. Receptor deficiency was confirmed by determining the ability of PTH, IL-1 alpha, and TNF-alpha to stimulate IL-6 in the media of primary calvaria-derived osteoblastic cell cultures from CD-1 and cytokine receptor-deficient mice. After 24 h of treatment, IL-1 alpha and TNF-alpha did not stimulate IL-6 production in osteoblasts from IL-1R1-/- and TNFR1-/- mice, respectively. In contrast, PTH increased IL-6 levels in the cells from all mice. IL-6 protein levels in bone marrow supernatants and conditioned media from untreated bone marrow stromal cells were undetectable in WILD, IL-1R1-/-, and TNFR1-/- mice. PTH, IL-1 alpha and TNF-alpha increased IL-6 mRNA and protein production in the WILD bone marrow stromal cells. In contrast, PTH and TNF-alpha increased IL-6 mRNA and protein levels in IL-1R1-/- bone marrow stromal cells while IL-1 alpha had no effect. These findings demonstrate that normal bone development in mice can occur in the absence of IL-1R1 or TNFR1 expression.

Effect of instruction to sing on stuttering frequency at normal and fast rates

Singing as a fluency-enhancing mechanism is well-established. The fluency derived by singing has been attributed to a reduced speech rate, memorized material, semantically reduced content, and an imposed rhythm. In this study, we attempted to address each of these explanations. 12 participants who stuttered were instructed to read or sing each of four different passages under the following conditions: reading at a normal rate, reading at a fast rate, singing at a normal rare, and singing at a fast rate. Participants exhibited a statistically significant increase in disfluencies while reading, i.e., participants displayed a 75% reduction in disfluency in the singing condition relative to the reading condition. There was no difference in stuttering frequency with rate conditions. Current findings suggest that stutterers are capable of internally generating fluent speech production by imposing idiosyncratic melodic structures or some derivation of melody when asked simply to sing. There is no claim that these participants were singing, as skills and capabilities varied tremendously, only that participants achieved dramatic enhancement of fluency after they were just asked to sing. Thus, the only intervening variable was the instruction to sing, which suggests the attempt to follow the instruction, no matter how futile, generated fluent speech. Since fluency was maintained in both the normal and fast rates of production, alternate central mechanisms must be held accountable for these findings.

Integration of narrow-host-range vectors from Escherichia coli into the genomes of amino acid-producing corynebacteria after intergeneric conjugation

Conjugative transfer of mobilizable derivatives of the Escherichia coli narrow-host-range plasmids pBR322, pBR325, pACYC177, and pACYC184 from E. coli to species of the gram-positive genera Corynebacterium and Brevibacterium resulted in the integration of the plasmids into the genomes of the recipient bacteria. Transconjugants appeared at low frequencies and reproducibly with a delay of 2 to 3 days compared with matings with replicative vectors. Southern analysis of corynebacterial transconjugants and nucleotide sequences from insertion sites revealed that integration occurs at different locations and that different parts of the vector are involved in the process. Integration is not dependent on indigenous insertion sequence elements but results from recombination between very short homologous DNA segments (8 to 12 bp) present in the vector and in the host DNA. In the majority of the cases (90%), integration led to cointegrate formation, and in some cases, deletions or rearrangements occurred during the recombination event. Insertions were found to be quite stable even in the absence of selective pressure.

A physical and genetic map of the Corynebacterium glutamicum ATCC 13032 chromosome

A combined physical and genetic map of the Corynebacterium glutamicum ATCC 13032 chromosome was constructed using pulsed-field gel electrophoresis (PFGE) and hybridizations with cloned gene probes. Total genomic DNA was digested with the meganucleases SwaI (5'-ATTTAAAT-3'), PacI (5'-TTAATTAA-3'), and PmeI (5'-GTTTAAAC-3') yielding 26,27, and 23 fragments, respectively. The chromosomal restriction fragments were then separated by PFGE. By summing up the lengths of the fragments generated with each of the three enzymes, a genome size of 3082 +/- 20 kb was determined. To identify adjacent SwaI fragments, a genomic cosmid library of C.glutamicum was screened for chromosomal inserts containing SwaI sites. Southern blots of the PFGE gels were hybridized with these linking clones to connect the SwaI fragments in their natural order. By this method, about 90% of the genome could be ordered into three contigs. Two of the remaining gaps were closed by cross-hybridization of blotted SwaI digests using as probes PacI and PmeI fragments isolated from PFGE gels. The last gap in the chromosomal map was closed by hybridization experiments using partial SwaI digestions, thereby proving the circularity of the chromosome. By hybridization of gene probes to SwaI fragments separated by PFGE about 30 genes, including rRNA operons, IS element and transposon insertions were localized on the physical map.

A Corynebacterium glutamicum gene encoding a two-domain protein similar to biotin carboxylases and biotin-carboxyl-carrier proteins

Following the analysis of transposon Tn5432-induced mutants of Corynebacterium glutamicum ATCC 13032, a gene encoding a protein with a biotin-binding motif was cloned. The DNA sequence of this gene revealed an open reading frame encoding 591 amino acids with a calculated mol. mass of 63.4 kDa. The protein is composed of two domains, an N-terminal biotin carboxylase and a C-terminal biotin-carboxyl-carrier protein, that are highly similar to corresponding subunits from prokaryotic and eukaryotic biotin enzymes. Over 70% identity was found to a protein from Mycobacterium leprae proposed to be part of an acyl-CoA carboxylase. Since it was not possible to inactivate the C. glutamicum gene, the gene most likely encodes a subunit of the essential acetyl-CoA carboxylase, which catalyzes the committed step in fatty acid synthesis.

Regulation of NFIL-6 and IL-6 expression by basic fibroblast growth factor in osteoblasts

We determined whether basic fibroblast growth factor (bFGF) regulated the expression of IL-6 and NFIL-6 in osteoblasts. In mouse osteoblastic MC3T3-E1 cells, bFGF (10(-8) M) increased NFIL-6 mRNA 2-fold at 30 minutes and 3-fold at 2 h. IL-6 mRNA was increased by bFGF 10(-8) M after 1 h. IL-6 protein was detectable in control cultures but was significantly increased by bFGF (10(-8) M) at 4 h. Immunofluorescence analysis of MC3T3-E1 cells showed primarily cytoplasmic and perinuclear NFIL-6 staining in control cultures while bFGF-treated cells showed increased NFIL-6 staining at 2 and 4 h. Western blotting revealed that bFGF increased NFIL-6 protein at 2 h. In calvarial mouse osteoblasts, bFGF 10(-8) M induced IL-6 mRNA as early as 1 h and significantly increased IL-6 protein levels as early as 2 h. In conclusion, bFGF stimulates IL-6 and NFIL-6 mRNA in osteoblasts. The increase in NFIL-6 mRNA was associated with increased NFIL-6 protein. The increase in IL-6 mRNA was also associated with increased IL-6 protein. We propose that activations of NFIL-6 and IL-6 may be important mediators of the effects of bFGF on bone cells.