Effects of ozone on activated sludge: performance of anaerobic digestion and structure of the microbial community

The treatment and disposal of activated sludge are currently challenging tasks in the world. As a common biological engineering technology, biological fermentation exists with disadvantages such as low efficiency and complex process. Ozone pretreatments are commonly applied to improve this problem due to their high efficiency and low cost. In this study, the significant function of ozone in anaerobic fermentation gas production was verified with excess sludge. Compared with other untreated sludge, ozone pretreatment can effectively degrade activated sludge. After ozone treatment and mixing with primary sludge, the methane production of excess sludge increased by 49.30 and 50.78%, and the methanogenic activity increased by 69.99 and 73.83%, respectively. The results indicated that the mixing of primary sludge with excess sludge possessed synergistic effects, which contributed to the anaerobic fermentation of excess sludge. The results of microbial community structure exhibited that methanogenic processes mainly involve hydrogenogens, acidogens and methanogens. The relative abundance of both bacteria and microorganisms changed significantly in the early stage of hydraulic retention time, which coincided exactly with the gas production stage. This study provided a feasible pretreatment strategy to improve sludge biodegradability and revealed the role of microorganisms during anaerobic digestion.

Preparation and characterization of 3D-printed antibacterial hydrogel with benzyl isothiocyanate

Benzyl isothiocyanate (BITC) is an isothiocyanate of plant origin, especially the mustard family, which has good antibacterial properties. However, its applications are challenging due to its poor water solubility and chemical instability. We used food hydrocolloids, including xanthan gum, locust bean gum, konjac glucomannan, and carrageenan as three-dimensional (3D)-printing food ink base and successfully prepared 3D-printed BITC antibacterial hydrogel (BITC-XLKC-Gel). The characterization and fabrication procedure of BITC-XLKC-Gel was studied. The results show that BITC-XLKC-Gel hydrogel has better mechanical properties by low-field nuclear magnetic resonance (LF-NMR), mechanical properties, and rheometer analysis. The strain rate of BITC-XLKC-Gel hydrogel is 76.5%, which is better than that of human skin. Scanning electron microscope (SEM) analysis showed that BITC-XLKC-Gel has uniform pore size and provides a good carrier environment for BITC carriers. In addition, BITC-XLKC-Gel has good 3D-printing performance, and 3D printing can be used for customizing patterns. Finally, inhibition zone analysis showed that the BITC-XLKC-Gel added with 0.6% BITC had strong antibacterial activity against Staphylococcus aureus and the BITC-XLKC-Gel added with 0.4% BITC had strong antibacterial activity against Escherichia coli. Antibacterial wound dressing has always been considered essential in burn wound healing. In experiments that simulated burn infection, BITC-XLKC-Gel showed good antimicrobial activity against methicillin-resistant S. aureus. BITC-XLKC-Gel is a good 3D-printing food ink attributed to strong plasticity, high safety profile, and good antibacterial performance and has great application prospects.

Transcriptome Analysis and Weighted Gene Co-expression Network Reveal Multitarget-Directed Antibacterial Mechanisms of Benzyl Isothiocyanate against Staphylococcus aureus

Staphylococcus aureus can cause many diseases and has a strong tendency to develop resistance to multiple antibiotics. In this study, benzyl isothiocyanate (BITC) was shown to have an excellent inhibitory effect on S. aureus ATCC25923 and methicillin-resistant S. aureus strains, with a minimum inhibitory concentration of 10 μg/mL. Under a scanning electron microscope, shrinkage and lysis of the cellular envelope were observed when exposed to BITC, and a bactericidal mode of BITC against S. aureus was further confirmed through flow cytometry. Additionally, the RNA profiles of S. aureus cells exposed to BITC indicated a violent transcriptional response to BITC. Through Kyoto Encyclopedia of Genes and Genomes analysis, it was found that many pathways involving bacterial survival were significantly affected, such as RNA degradation, oxidative phosphorylation, arginine biosynthesis, and so forth. A gene co-expression network was constructed using weighted gene co-expression network analysis, and six biologically meaningful co-expression modules and 125 hub genes were identified from the network. Among them, EfeB, GroES, SmpB, and Lsp were possibly targeted by BITC, leading to the death of S. aureus. Our results indicated a great potential of BITC to be applied in food safety and pharmaceuticals, highlighting its multitarget-directed bactericidal effects on S. aureus.

Accelerating vinegar aging by combination of ultrasonic and magnetic field assistance

Most fermented foods need a natural aging process to enrich desired flavours. This process is normally the bottleneck for cost-effective production. Therefore, it is desirable to accelerate the process and obtain products with the same flavour profile. Here, we used physical interventions (ultrasonic field, alternating magnetic field, or combination of both) to assist the aging process with naturally brewed vinegar as a case example. Flavour profiles of different physical-assisted aging process were compared with that of the naturally aged vinegar by using gas-chromatography mass-spectrometry (GC-MS) and electronic nose. Principal component analysis (PCA) and Pearson correlation analyses show that ultrasonic and alternating magnetic fields treatment could accelerate the aging process of vinegar. The highest accelerating aging effect was combination of ultrasonic and magnetic field followed by individual ultrasonic or magnetic field and natural process (combination of ultrasonic and magnetic field > ultrasonic or magnetic field individual > natural process). These results suggest that physical field intervention could potentially be used for acceleration of aging of fermented products without affecting flavour quality.

High-throughput screening identifies small molecules that enhance the pharmacological effects of oligonucleotides

The therapeutic use of antisense and siRNA oligonucleotides has been constrained by the limited ability of these membrane-impermeable molecules to reach their intracellular sites of action. We sought to address this problem using small organic molecules to enhance the effects of oligonucleotides by modulating their intracellular trafficking and release from endosomes. A high-throughput screen of multiple small molecule libraries yielded several hits that markedly potentiated the actions of splice switching oligonucleotides in cell culture. These compounds also enhanced the effects of antisense and siRNA oligonucleotides. The hit compounds preferentially caused release of fluorescent oligonucleotides from late endosomes rather than other intracellular compartments. Studies in a transgenic mouse model indicated that these compounds could enhance the in vivo effects of a splice-switching oligonucleotide without causing significant toxicity. These observations suggest that selected small molecule enhancers may eventually be of value in oligonucleotide-based therapeutics.

TBX6 null variants and a common hypomorphic allele in congenital scoliosis

BACKGROUND

Congenital scoliosis is a common type of vertebral malformation. Genetic susceptibility has been implicated in congenital scoliosis.

METHODS

We evaluated 161 Han Chinese persons with sporadic congenital scoliosis, 166 Han Chinese controls, and 2 pedigrees, family members of which had a 16p11.2 deletion, using comparative genomic hybridization, quantitative polymerase-chain-reaction analysis, and DNA sequencing. We carried out tests of replication using an additional series of 76 Han Chinese persons with congenital scoliosis and a multicenter series of 42 persons with 16p11.2 deletions.

RESULTS

We identified a total of 17 heterozygous TBX6 null mutations in the 161 persons with sporadic congenital scoliosis (11%); we did not observe any null mutations in TBX6 in 166 controls (P<3.8×10(-6)). These null alleles include copy-number variants (12 instances of a 16p11.2 deletion affecting TBX6) and single-nucleotide variants (1 nonsense and 4 frame-shift mutations). However, the discordant intrafamilial phenotypes of 16p11.2 deletion carriers suggest that heterozygous TBX6 null mutation is insufficient to cause congenital scoliosis. We went on to identify a common TBX6 haplotype as the second risk allele in all 17 carriers of TBX6 null mutations (P<1.1×10(-6)). Replication studies involving additional persons with congenital scoliosis who carried a deletion affecting TBX6 confirmed this compound inheritance model. In vitro functional assays suggested that the risk haplotype is a hypomorphic allele. Hemivertebrae are characteristic of TBX6-associated congenital scoliosis.

CONCLUSIONS

Compound inheritance of a rare null mutation and a hypomorphic allele of TBX6 accounted for up to 11% of congenital scoliosis cases in the series that we analyzed. (Funded by the National Basic Research Program of China and others.).

Esophageal squamous cell carcinoma (ESCC): advance in genomics and molecular genetics

Esophageal cancer is aggressive and has poor prognosis. Esophageal squamous cell carcinoma (ESCC) is histologically the most prevalent type of esophageal cancer and ranked as the sixth leading cause of cancer death worldwide. In recent years, cancer has been widely regarded as genetic disease, as well as epigenetic abnormalities including DNA methylation, histone deacetylation, chromatin remodeling, gene imprinting and noncoding RNA regulation. In this review, we will provide a general overview of genes, proteins and microRNAs that are involved in the development of ESCC, which aims to enhance our understanding of molecular mechanisms implicated in ESCC development and progression.

MiR-324-5p inhibits proliferation of glioma by target regulation of GLI1

OBJECTIVES

To study the effects of the miR-324-5p on the glioma cells proliferation via the targeted regulation of the glioma-associated oncogene 1.

METHODS

The luciferase reporter gene was used to test whether the glioma-associated oncogene 1 was the target of the miR-324-5p microRNA. The glioma-associated oncogene 1 expression was detected by Western blot. The proliferation and cell cycle were evaluated by MTT assay and flow cytometry.

RESULTS

The glioma-associated oncogene 1 is a target of the miR-324-5p. An over-expressed miR-324-5p could reduce the cell survival rate and increase the G1/G0 phase rate in the glioma cell lines.

CONCLUSIONS

The miR-324-5p can inhibit proliferation of the glioma cells via the targeted regulation of the glioma-associated oncogene 1.

Receptors, endocytosis, and trafficking: the biological basis of targeted delivery of antisense and siRNA oligonucleotides

The problem of targeted delivery of antisense and siRNA oligonucleotides can be resolved into two distinct aspects. The first concerns devising ligand-oligonucleotide or ligand-carrier moieties that bind with high selectivity to receptors on the cell type of interest and that are efficiently internalized by endocytosis. The second concerns releasing oligonucleotides from pharmacologically inert endomembrane compartments so that they can access RNA in the cytosol or nucleus. In this review, we will address both of these aspects. Thus, we present information on three important receptor families, the integrins, the receptor tyrosine kinases, and the G protein-coupled receptors in terms of their suitability for targeted delivery of oligonucleotides. This includes discussion of receptor abundance, internalization and trafficking pathways, and the availability of suitable high affinity ligands. We also consider the process of oligonucleotide uptake and intracellular trafficking and discuss approaches to modulating these processes in a pharmacologically productive manner. Hopefully, the basic information presented in this review will be of value to investigators involved in designing delivery approaches for oligonucleotides.

SU-E-I-75: A New Method for Prostate Cancer Localization Using Multispectral MRI

PURPOSE

To develop a new method for automatic localization of prostate cancer using multispectral MRI data.

METHODS

Multispectral MRI including MR spectroscopic imaging (MRSI), T2 weighted MRI, diffusion weighted imaging (DWI) and dynamic contrast-enhanced (DCE) MRI, has been used for cancer target localization. The combination of multiple MRI imaging technologies provides more useful information than one single technology alone about prostate cancer and has advantages for target definition in radotherapy treatment and quantitative evaluation of tumor response. However, manual cancer localization using multispectral MRI dataset is a tedious task and prone to inter-/intra-observer variability. Automatic localization methods using multispectral MRI data is highly desired. In this paper, a fuzzy fusion framework for automatically localizing prostate cancer with multispectral MRI data is presented. Firstly, for each kind of MRI images, a membership function is created to calculate the membership-degrees of image elements belonging to cancer region. Secondly, a fuzzy fusion operator is used to fuse different membership- degrees corresponding to the same regions. Lastly, the Result of fusion is further adjusted with fuzzy region growing process, leading to the final membership-degree map. And cancer volume is finally defined by setting up a threshold on the map.

RESULTS

The new method was tested with one multispectral MRI patient dataset and results from our experimental study are compared with the one obtained form a manual method performed by an experienced pathologist. Quantitative analysis shows that the specificity is 98.89%, sensitivity is 62.85% and accuracy is 95.42%, respectively. It illustrates the feasibility of utilizing this framework in the clinical application.

CONCLUSIONS

The feasibility study shows the new method reported in this paper achieves automatic localization for prostate cancer and can be easily implemented in clinical applications. We are currently conducting a clinical study for testing the effectiveness and reliability, and further developing this method. *supported by NSFC-81171342 support by National Science Foundation of China (NSFC-81171342).

Biological barriers to therapy with antisense and siRNA oligonucleotides

Attaining the full therapeutic utility of antisense and siRNA oligonucleotides will require understanding of the biological barriers that stand between initial administration of these drugs and their final actions within cells. This review examines some of the key barriers that affect the biodistribution of oligonucleotides both in molecular form and when they are associated with nanocarriers. An understanding of the biological processes underlying these barriers will aid in the design of more effective delivery systems.

Effect of Allium sativum (garlic) diallyl disulfide (DADS) on human non-small cell lung carcinoma H1299 cells

This study was undertaken to elucidate the effect of diallyl disulfide from Allium sativum, an oil-soluble organosulfur compound found in garlic, in suppressing human non-small cell lung carcinoma H1299 cells. A potent increase in apoptotic cells has accompanied 1) a decrease in cell viability, 2) an increase of the fraction of G2/M-phase cells by up to 48.80 %, and 3) a transient increase of the phospho-p42/44 (phosphorylated p42/44 MAPK) in a time- and concentration-dependent manner. These results indicated that diallyl disulfide could induce apoptosis in human non-small cell lung carcinoma H1299 cells via, at least partly, G2/M-phase block of the cell cycle, related to a rise in MAPK phosphorylation.

Prenatal and birth complications in autism

OBJECTIVES

Prenatal and birth history as potential sources of risk factors in relation to the onset of autism were examined.

METHODS

A cohort of 164 families of autistic children referred to The Autism Center at New Jersey Medical School-UMDNJ, Newark, New Jersey, over a two-year period was studied. Intake prenatal and birth history information was obtained from each family and reviewed by a clinician.

RESULTS

Prevalence rates in this cohort for vaginal bleeding, prolonged labor and prematurity were higher than comparable rates reported nationally and in New Jersey. Clustering of multiple prenatal risk factors was observed. This clustering was associated with the age of the mother, but uncorrelated with birth order.

CONCLUSIONS

These findings support the general hypothesis that systemic problems at the prenatal stage may form a distinct dimension of risk associated with autism.

L-nucleosides containing modified nucleobases

The synthesis of base modified L-nucleosides is described with pyrrolo[2,3-d]pyrimidines, pyrazolo[3,4-d]pyrimidines, benzimidazoles, and imidazo[1,2-a]-s-triazines as nucleobases. The conformation of the nucleosides is studied and the antiviral activity is evaluated.

Increased excretion of a lipid peroxidation biomarker in autism

It is thought that autism could result from an interaction between genetic and environmental factors with oxidative stress as a potential mechanism linking the two. One genetic factor may be altered oxidative-reductive capacity. This study tested the hypothesis that children with autism have increased oxidative stress. We evaluated children with autism for the presence of two oxidative stress biomarkers. Urinary excretion of 8-hydroxy-2-deoxyguanosine (8-OHdG) and 8-isoprostane-F2alpha (8-iso-PGF2alpha) were determined in 33 children with autism and 29 healthy controls. 8-iso-PGF2alpha levels were significantly higher in children with autism. The isoprostane levels in autistic subjects were variable with a bimodal distribution. The majority of autistic subjects showed a moderate increase in isoprostane levels while a smaller group of autistic children showed dramatic increases in their isoprostane levels. There was a trend of an increase in 8-OHdG levels in children with autism but it did not reach statistical significance. There was no significant correlation between the levels of the biomarkers and vitamin intake, dietary supplements, medicine, medical disorders, or history of regression. These results suggest that the lipid peroxidation biomarker is increased in this cohort of autistic children, especially in the subgroup of autistic children.

Genetic transformation of two species of orchid by biolistic bombardment

We report here the transformation of two species of orchid, Dendrobium phalaenopsis and D. nobile,by biolistic bombardment. Calli or protocorm-like bodies (PLBs) were used as target explants. Gold particles (1.0 microm) coated with plasmid DNA (pCAMBIA1301) encoding an intron-containing beta-glucuronidase gene (gus-int) and a hygromycin phosphotransferase (hpt) gene were introduced into the PLBs or calli using the Bio-Rad PDS-1000/He Biolistic Particle Delivery System. Calli and PLBs were then chopped up and pre-cultured in 1/2-strength MS medium supplemented with 0.4 M mannitol for a 1-h osmoticum treatment before bombardment. Immediately after bombardment, the calli and PLBs were transferred to 1/2-strength MS medium without mannitol for recovery. Putatively transformed plantlets were obtained by selection and regeneration on medium supplemented with 30 mg/l hygromycin. The highest efficiency of transformation was obtained when selection was conducted at 2 days post-bombardment. For D. phalaenopsis and D. nobile, respectively, about 12% and 2% of the bombarded calli or PLBs produced independent transgenic plants. Integration and expression of the transgenes were confirmed by Southern hybridization and Northern hybridization. No nontransformed plants were regenerated, indicating a tight selection scheme. However, separate incorporation of the gus gene and the hpt gene was observed, and in one transgenic line the gus gene was integrated into the genome of the transgenic plant, but not expressed.

Proliferating oligodendrocytes are present in both active and chronic inactive multiple sclerosis plaques

The proliferation marker Ki-67 labels cell nuclei in the G(1), S, M, and G(2) phases of the cell cycle. We used Ki-67 immunohistochemistry to quantify proliferating glial cells in brain tissue sections from twenty-four patients, comprised of multiple sclerosis, normal brains, and other neurological disease controls. Glial proliferation was greatly increased in MS lesions when compared with control brain white matter. Both actively demyelinating/early remyelinating plaques and chronic inactive plaques of long standing often displayed large numbers of glial cells in the proliferative cycle. The bulk of these proliferating cells were of oligodendroglial lineage in the MS plaques. Ki-67 positive macrophage/microglial lineage cells were largely restricted to acute lesions. The finding of increased numbers of proliferating oligodendroglia in most MS plaques, regardless of disease duration or activity state, indicates that the MS brain is capable of recruiting unexpectedly large numbers of new oligodendrocytes over long periods of time. The factors within the MS plaque microenvironment that provoke new oligodendrocyte generation and their subsequent loss still need to be identified.

Cavernous angioma of the brain stem simulating diffuse pontine glioma

Brainstem vascular malformations can sometimes simulate other conditions such as multiple sclerosis and pontine glioma. We report a case of brainstem cavernous angioma for which clinical course and radiologic appearance were suggestive of a pontine glioma. The diagnosis was uncertain until the clinical and radiologic evolution made it clear that the patient had a cavernous angioma. We suggest that brainstem angioma be considered as a differential diagnosis for pontine glioma.

Up-regulated p75NTR neurotrophin receptor on glial cells in MS plaques

OBJECTIVE

To investigate the expression of the neurotrophin receptor p75NTR on glial cells within MS plaques.

BACKGROUND

In recent studies on the pathogenesis of MS white matter plaques, we found large populations of inflammatory and resident glial cells, including oligodendrocytes undergoing cell death, and identified increased expression of Fas receptor and ligand death pathway signaling molecules on the same glial cell types. In another study, the p75NTR was shown to induce apoptotic death of maturing oligodendrocytes when exposed to NGF in vitro.

METHODS

We used immunohistochemistry and in situ reverse-transcription PCR to detect p75NTR expression on inflammatory and resident glial cells in MS plaques and used TUNEL staining for fragmented DNA to detect cell death.

RESULTS

Up-regulated p75NTR messenger RNA and protein were demonstrated in both oligodendrocytes and microglia/macrophages in MS plaques but not in control white matter. However, only a fraction of p75NTR expressing oligodendrocytes was also stained by TUNEL.

CONCLUSIONS

Glial cell expression of p75NTR receptor is up-regulated during MS plaque formation. The exact role of this receptor in glial cell death and/or survival in MS remains to be elucidated.

[A preliminary report of the effect of levodopa and carbidopa for childhood amblyopia]

PURPOSE

To explore the short-term effect of levodopa and carbidopa in 36 children (4.5-14 years) with refractory amblyopia.

METHODS

36 cases of incurable childhood amblyopia treated with occlussion with visual acuity stably for 6 months were retreated by levodopa and carbidopa 1.5 mg/kg, 0.38 mg/kg respectively for 3 months. Visual acuity, fusional and stereoscopic function, retinal light sensitivity and scotomas were observed at 1 and 3 months after tablet taken. Medicine side effects were observed.

RESULTS

At 3 months, the visual acuity of 88.89% eyes were improved(average 2.27 +/- 1.26 line), fusional and stereoscopic function were restored in 10 and 6 cases respectively. Retinal light sensitivity significantly increased, scotomas disappeared in 19 eyes and contracted in 6 eyes. The basic cure rate was 42.86% Less side effect were found.

CONCLUSION

Average dose levels(1.5/0.38 mg/kg) of levodopa and carbidopa were an effective and secuity method to improve visual function of refractory childhood amblyopia.

Fixation-off and eyes closed catamenial generalized nonconvulsive status epilepticus with eyelid myoclonic jerks

PURPOSE

Eyelid myoclonic jerks have been described in fixation-off-sensitive (FOS) epilepsy, but their relationship to nonconvulsive status epilepticus (NCSE) or to catamenial exacerbations is little reported.

METHODS

We describe a woman of normal intelligence with catamenial periods of prolonged NCSE who exhibited various intra- and interseizure thresholds of polyspike suppression when her eyes were open, with particular visual inputs and with antiepileptic drug (AED) treatment.

RESULTS

In one episode, on the first day of the woman's menstrual period, bursts of bilateral synchronous polyspike activity were briefly suppressed with visual fixation but were more lastingly suppressed after administration of lorazepam (LZP). During another period of NCSE, the SE was completely suppressed by visual fixation on objects and patterned checkerboard screens and by ocular convergence, was incompletely suppressed when her eyes were open in a dark room and when her eyes were open without visual fixation, but was not suppressed by mental activation alone.

CONCLUSIONS

FOS polyspike bursts with eyelid myoclonic jerks may exhibit catamenial exacerbations, varying from completely suppressible with visual fixation to nonsuppressible during NCSE. These findings suggest an interplay between humoral factors, AEDs, and seizure threshold in this condition.

Rice dwarf phytoreovirus segment S11 encodes a nucleic acid binding protein

The function of rice dwarf virus segment 11 and the corresponding segments of other phytoreoviruses is not yet determined. The amino acid sequence of Pns11, encoded by segment 11, contains a putative zinc finger and five flanking basic regions at the C-terminus. The full-length Pns11 protein and three truncated derivatives, which lack the N-terminus, the zinc-finger or the C-terminal five basic regions were expressed in Escherichia coli and their nucleic acid binding properties were studied. Pns11 interacts with single- and double-stranded forms of DNA and RNA in a sequence-nonspecific manner. The truncated derivative which contains both the zinc-finger and the C-terminal basic regions has the same binding properties as the full-length Pns11. However, removal of either of these domains prevents binding activity. The binding activity of Pns11 was drastically reduced when the blots were treated with a high concentration of EDTA. Moreover, Pns11 extracted from infected rice also binds to single-stranded RNA. These data suggest that RDV Pns11 binding activity is structure-dependent and it may play an important role in virus replication and/or genome assortment.

[Effect of dietary selenium and germanium on the precancerous lesion in rat glandular stomach induced by N-methyl-N'-nitro-N-nitrosoguanidine]

N-Methyl-N'-nitrosoguanidine (MNNG) was administered (100 mg/L) in drinking water in 100 Wistar rats for 24 weeks to induce the precancerous lesion in glandular stomach. 77 rats with the precancerous lesion in glandular stomach were divided into 3 groups randomly at the 25 thweek. Yeast selenium (Yse, 4 mg/L) and carboxyethyl germanium sesquioxide (Ge-132, 600 mg/L) in drinking water were administered respectively in the corresponding treatment groups: 100 ml/MNNG in drinking water was administered in the treatment group, and 100 ml/MNN in drinking water was administered in the treatment group and control group for another 5 weeks. The experiment ended at the end of the 37th week. The results showed that the incidence of glandular stomach cancer in the Yse group was significantly lower than that in the control group; the infiltrating depth of glandular stomach cancer in the Yse group and the Ge-132 group was remarkably shallower than that in the control group. These findings suggest that Yse and Ge-132 have some preventive effect on the precancerous lesion in rat glandular stomach induced by MNNG.

Structure of a precursor to the yeast mitochondrial tRNAMetf. Implications for the function of the tRNA synthesis locus

A transcript from the yeast mitochondrial tRNAMetf gene has been isolated from a petite deletion mutant, ND40. RNA sequence analysis demonstrates that it has a 5' unprocessed extension of 28 nucleotides, and capping experiments with guanylyltransferase reveal that the first nucleotide has a 5' di- or triphosphate. A comparison of the RNA sequence with the tRNAMetf gene sequence reported here shows that transcription initiation occurs at a sequence homologous to a nonanucleotide segment implicated as a promoter element of yeast mitochondrial DNA. The 3' end of this transcript is identical to the mature tRNAMetf and carries a CCA sequence. The transcript can be processed in vitro to yield a mature tRNAMetf and thus appears to be a bona fide tRNA precursor. This tRNA precursor accumulates in the absence of the mitochondrial tRNA synthesis locus whereas mature tRNAMetf can be made from the same gene in the presence of the locus. This data provides clear and convincing evidence that the synthesis locus codes for a 5' tRNA processing function.