Preventing the recurrence of depression with a Mediterranean diet supplemented with extra-virgin olive oil. The PREDI-DEP trial: study protocol

BACKGROUND

The role of dietary patterns in the prevention of unipolar depression has been analyzed in several epidemiological studies. The primary aims of this study are to determine the effectiveness of an extra-olive oil-enriched Mediterranean diet in reducing the recurrence of depression and improving the symptoms of this condition.

METHODS

Multicenter, two-arm, parallel-group clinical trial. Arm 1, extra-virgin olive oil Mediterranean diet; Arm 2, control group without nutritional intervention. Dieticians are in charge of the nutritional intervention and regular contact with the participants. Contacts are made through our web platform ( https://predidep.es/participantes/ ) or by phone. Recurrence of depression is assessed by psychiatrists and clinical psychologists through clinical evaluations (semi-structured clinical interviews: Spanish SCID-I). Depressive symptoms are assessed with the Beck Depression Inventory. Information on quality of life, level of physical activity, dietary habits, and blood, urine and stool samples are collected after the subject has agreed to participate in the study and once a year.

DISCUSSION

To the best of our knowledge, the PREDI-DEP trial is the first ongoing randomized clinical trial designed to assess the role of the Mediterranean diet in the prevention of recurrent depression. It could be a cost-effective approach to avoid recurrence and improve the quality of life of these patients.

TRIAL REGISTRATION

The study has been prospectively registered in the U.S. National Library of Medicine ( https://clinicaltrials.gov ) with NCT number: NCT03081065.

The Cek1‑mediated MAP kinase pathway regulates exposure of α‑1,2 and β‑1,2‑mannosides in the cell wall of Candida albicans modulating immune recognition

The Cek1 MAP kinase (MAPK) mediates vegetative growth and cell wall biogenesis in the fungal pathogen Candida albicans. Alterations in the fungal cell wall caused by a defective Cek1‑mediated signaling pathway leads to increased β‑1,3‑glucan exposure influencing dectin‑1 fungal recognition by immune cells. We show here that cek1 cells also display an increased exposure of α‑1,2 and β‑1,2‑mannosides (α‑M and β‑M), a phenotype shared by strains defective in the activating MAPKK Hst7, suggesting a general defect in cell wall assembly. cek1 cells display walls with loosely bound material as revealed by transmission electron microscopy and are sensitive to tunicamycin, an inhibitor of N‑glycosylation. Transcriptomal analysis of tunicamycin treated cells revealed a differential pattern between cek1 and wild type cells which involved mainly cell wall and stress related genes. Mapping α‑M and β‑M epitopes in the mannoproteins of different cell wall fractions (CWMP) revealed an important shift in the molecular weight of the mannan derived from mutants defective in this MAPK pathway. We have also assessed the role of galectin‑3, a member of a β‑galactoside‑binding protein family shown to bind to and kill C. albicans through β‑M recognition, in the infection caused by cek1 mutants. Increased binding of cek1 to murine macrophages was shown to be partially blocked by lactose. Galectin-3(-/-) mice showed increased resistance to fungal infection, although galectin-3 did not account for the reduced virulence of cek1 mutants in a mouse model of systemic infection. All these data support a role for the Cek1‑mediated pathway in fungal cell wall maintenance, virulence and antifungal discovery.

A schizophrenia-like psychotic disorder secondary to an arachnoid cyst remitted with neurosurgical treatment of the cyst

We describe a case of delusional psychosis that was terminated by neurosurgical removal of a large arachnoid cyst. The patient was suffering his first psychotic episode and had symptoms typical of schizophrenia.

The case underscores the importance of considering that an arachnoid cyst can induce psychopathological symptoms, even those of schizophrenia. Indeed, such symptoms may be the cyst's only clinical manifestation.

In addition, the case highlights the importance of doing a structural imaging test when confronted with a first episode of psychosis, especially if the episode is relatively late in appearance. Such imaging may lead to a diagnosis that in turn can enable a definitive neurosurgical resolution of the psychosis.

Fungi sensing environmental stress

Cells need to adapt to the external environment in order to survive. Signal transduction pathways are crucial mechanisms that allow cells to sense and respond to extracellular stimuli. Among the signal transduction pathways, we point out the cascades mediated by mitogen-activated protein kinases (MAPKs). The MAPKs are conserved from yeast to human and play relevant roles in the physiology of the cell. In pathogenic fungi these MAPK pathways control virulence factors. This review describes the MAPK cascades described in Candida albicans, the most frequently isolated fungus, from fungal systemic infections among individuals in developed countries.

Association between folate, vitamin B(6) and vitamin B(12) intake and depression in the SUN cohort study

BACKGROUND

An association between low blood levels of folate, vitamins B(6) and B(12) and a higher prevalence of depressive symptoms has been reported in several epidemiological studies. The present study aimed to assess the association between folate, vitamins B(6) and B(12) intake and depresion prevalence in the SUN cohort study.

METHODS

The study comprised a cross-sectional analysis of 9670 participants. A validated semi-quantitative food frequency questionnaire was used to ascertain vitamin intake. The association between the baseline intake of folate, vitamins B(6) and B(12) categorised in quintiles and the prevalence of depression was assessed. The analyses were repeated after stratifying by smoking habits, alcohol intake, physical activity and personality traits.

RESULTS

Among women, odds ratios (OR) [95% confidence interval (CI)] for the third to fifth quintile for vitamin B(12) intake were 0.58 (0.41-0.84), 0.56 (0.38-0.82) and 0.68 (0.45-1.04), respectively. Among those men with a low level of anxiety and current smokers, a significant positive association between low folate intake and the prevalence of depression was found. The OR (95% CI) for the first quintile of intake was 2.85 (1.49-5.45) and 2.18 (1.08-4.38), respectively, compared to the upper quintiles of intake (Q2-Q5) considered as a group.

CONCLUSION

Low folate intake was associated with depression among currently smoking men and men with low anxiety levels. Low intake of vitamin B(12) was associated with depression among women. No significant associations were found for vitamin B(6) intake.

The Cek1 and Hog1 mitogen-activated protein kinases play complementary roles in cell wall biogenesis and chlamydospore formation in the fungal pathogen Candida albicans

The Hog1 mitogen-activated protein (MAP) kinase mediates an adaptive response to both osmotic and oxidative stress in the fungal pathogen Candida albicans. This protein also participates in two distinct morphogenetic processes, namely the yeast-to-hypha transition (as a repressor) and chlamydospore formation (as an inducer). We show here that repression of filamentous growth occurs both under serum limitation and under other partially inducing conditions, such as low temperature, low pH, or nitrogen starvation. To understand the relationship of the HOG pathway to other MAP kinase cascades that also play a role in morphological transitions, we have constructed and characterized a set of double mutants in which we deleted both the HOG1 gene and other signaling elements (the CST20, CLA4, and HST7 kinases, the CPH1 and EFG1 transcription factors, and the CPP1 protein phosphatase). We also show that Hog1 prevents the yeast-to-hypha switch independent of all the elements analyzed and that the inability of the hog1 mutants to form chlamydospores is suppressed when additional elements of the CEK1 pathway (CST20 or HST7) are altered. Finally, we report that Hog1 represses the activation of the Cek1 MAP kinase under basal conditions and that Cek1 activation correlates with resistance to certain cell wall inhibitors (such as Congo red), demonstrating a role for this pathway in cell wall biogenesis.

The MAP kinase signal transduction network in Candida albicans

MAP (mitogen-activated protein) kinase-mediated pathways are key elements in sensing and transmitting the response of cells to environmental conditions by the sequential action of phosphorylation events. In the fungal pathogenCandida albicans, different routes have been identified by genetic analysis, and especially by the phenotypic characterization of mutants altered in the Mkc1, Cek1/2 and Hog1 MAP kinases. The cell integrity (orMKC1-mediated) pathway is primarily involved in the biogenesis of the cell wall. The HOG pathway participates in the response to osmotic stress while the Cek1 pathway mediates mating and filamentation. Their actual functions are, however, much broader and Mkc1 senses several types of stress, while Hog1 is also responsive to other stress conditions and participates in two morphogenetic programmes: filamentation and chlamydospore formation. Furthermore, it has been recently shown that Cek1 participates in a putative pathway involved in the construction of the cell wall and which seems to be operative under basal conditions. As these stimuli are frequently encountered in the human host, they provide a reasonable explanation for the significant reduction in pathogenicity that several signal transduction mutants show in certain animal models of virulence. MAPK pathways therefore represent an attractive multienzymic system for which novel antifungal therapy could be designed.

The Importance of the Phagocytes' Innate Response in Resolution of the Infection Induced by a Low Virulent Candida albicans Mutant

We have reported that a Candida albicans mkc1Delta/mkc1Delta mutant, deleted in the Mkc1p mitogen-activated protein kinase, an essential element of the cell integrity signalling pathway, has reduced virulence in a murine model of systemic infection. We analyse here the immunological basis for this feature in view of its failure to vaccinate. Firstly, the influence of the Th response was analysed by infecting different knockout mice, revealing the importance of interferon-gamma in the resolution of mkc1 systemic infection. Secondly, the role of innate immunity was studied. The infection of neutropenic mice revealed that the candidacidal activity of neutrophils is crucial during the first 3 days of infection for the mutant strain. Macrophages played a critical role in the clearance of infection. Although a similar anti-Candida activity was found for both fungal strains with naïve macrophages, activated macrophages discriminated between both strains. In vitro experiments revealed that the mutant strain displayed a greater susceptibility to nitric oxide (NO), a reduced inhibitory effect on macrophage NO production and an increased capacity of macrophage stimulation by cell wall extracts. The importance of NO in systemic infection with the mutant strain was confirmed by the strong increase in the susceptibility of aminoguanidine (an iNOs inhibitor)-treated mice.

Strategies for the identification of virulence determinants in human pathogenic fungi

The incidence of fungal infections is increasing in different countries. The current available therapy of these infections does not satisfy all requirements in terms of specificity and therapeutic index, a fact that has stimulated the scientific community to identify fungal virulence determinants. Several pathogenic fungi are opportunistic and, therefore, identification of virulence genes is difficult, given their close relationship with host cells. In recent years, the development of genetic tools in several pathogenic fungi has enabled the development of genetic strategies for their identification. These include several strategies based on the phenotypic analysis of strains or environmental conditions in which the expression of the putative gene(s) is either altered or deleted; and this is accomplished through the development of in vitro or in vivo systems. In the near future, this research will produce a better picture of fungal pathogenesis and therefore define novel promising targets in antifungal therapy.

Large-scale identification of putative exported proteins in Candida albicans by genetic selection

In all living organisms, secreted proteins play essential roles in different processes. Of special interest is the construction of the fungal cell wall, since this structure is absent from mammalian cells. The identification of the proteins involved in its biogenesis is therefore a primary goal in antifungal research. To perform a systematic identification of such proteins in Candida albicans, we carried out a genetic screening in which in-frame fusions with an intracellular allele of invertase gene SUC2 of Saccharomyces cerevisiae can be used to select and identify putatively exported proteins in the heterologous host S. cerevisiae. Eighty-three clones were selected, including 11 previously identified genes from C. albicans as well as 41 C. albicans genes that encode proteins homologous to already described proteins from related organisms. They include enzymes involved in cell wall synthesis and protein secretion. We also found membrane receptors and transporters presumably related to the interaction of C. albicans with the environment as well as extracellular enzymes and proteins involved in different morphological transitions. In addition, 11 C. albicans open reading frames (ORFs) identified in this screening encode proteins homologous to unknown or putative proteins, while 5 ORFs encode novel secreted proteins without known homologues in other organisms. This screening procedure therefore not only identifies a set of targets of interest in antifungal research but also provides new clues for understanding the topological locations of many proteins involved in processes relevant to the pathogenicity of this microorganism.

Signal transduction pathways and cell-wall construction in Candida albicans

Signal transduction pathways are the molecular mechanisms responsible for detecting and transmitting changes in the surrounding environment to the nucleus where appropriate responses are generated. The cell wall is the most external structure of the fungal cell and, in pathogenic fungi, is responsible for specifically interacting with the mammalian host cell in a highly dynamic interplay. Recent work has shown the role that some signal transduction pathways, involving members of the MAP kinase family, have in this process in the nonpathogenic model organism Saccharomyces cerevisiae. However, as yet little is known about these phenomena in pathogenic fungi. The aim of this review is to characterize the existing signal transduction pathways in Candida albicans and their relationship with the cell-wall construction.

Virulence genes in the pathogenic yeast Candida albicans

In recent years, the incidence of fungal infections has been rising all over the world. Although the amount of research in the field of pathogenic fungi has also increased, there is still a need for the identification of reliable determinants of virulence. In this review, we focus on identified Candida albicans genes whose deletant strains have been tested in experimental virulence assays. We discuss the putative relationship of these genes to virulence and also outline the use of new different systems to examine the precise effect in virulence of different genes.

Recent developments in molecular genetics of Candida albicans

The frequency of opportunistic infections caused by the fungus Candida albicans is very high and is expected to continue to increase as the number of immunocompromised patients rises. Research initiatives to study the biology of this organism and elucidate its pathogenic determinants have therefore expanded significantly during the last 5-10 years. The past few years have also brought continuous improvement in the techniques to study gene function by gene inactivation and by regulated gene expression and to study gene expression and protein localization by using gene reporter systems. As steadily more genomic sequence information from this human fungal pathogen becomes available, we are entering a new era in antimicrobial research. However, many of the currently available molecular genetics tools are poorly adapted to a genome-wide functional analysis in C. albicans, and further development of these tools is hampered by the asexual and diploid nature of this organism. This review outlines recent advances in the development of molecular tools for functional analysis in C. albicans and summarizes current knowledge about the genomic and genetic variability of this important human fungal pathogen.

Protein localisation approaches for understanding yeast cell wall biogenesis

Yeast cells are surrounded by the cell wall, a rigid but dynamic structure that is essential for their viability. The complexity and functionality of this structure suggest that a high number of proteins must be involved in the biogenesis of the cell wall architecture and, as a consequence, in the maintenance of cell integrity. Among them, a high percentage is assumed to be located at the cell surface, mostly as structural or enzymatic components of the cell wall. Therefore, the presence of a protein in the cell wall is suggestive of its cell wall-related function. Different techniques can be used to specifically detect the cell wall localisation of a given protein or to identify cell wall proteins in large-scale analyses. These include the detection of proteins in whole cells or specific cell wall fractions by immunological, biochemical, microscopic, or genetic approaches, as well as the emerging proteomic technology. The advantages, limitations, and usefulness of these techniques are discussed and illustrated with some examples.

Role of the mitogen-activated protein kinase Hog1p in morphogenesis and virulence of Candida albicans

The relevance of the mitogen-activated protein (MAP) kinase Hog1p in Candida albicans was addressed through the characterization of C. albicans strains without a functional HOG1 gene. Analysis of the phenotype of hog1 mutants under osmostressing conditions revealed that this mutant displays a set of morphological alterations as the result of a failure to complete the final stages of cytokinesis, with parallel defects in the budding pattern. Even under permissive conditions, hog1 mutants displayed a different susceptibility to some compounds such as nikkomycin Z or Congo red, which interfere with cell wall functionality. In addition, the hog1 mutant displayed a colony morphology different from that of the wild-type strain on some media which promote morphological transitions in C. albicans. We show that C. albicans hog1 mutants are derepressed in the serum-induced hyphal formation and, consistently with this behavior, that HOG1 overexpression in Saccharomyces cerevisiae represses the pseudodimorphic transition. Most interestingly, deletion of HOG1 resulted in a drastic increase in the mean survival time of systemically infected mice, supporting a role for this MAP kinase pathway in virulence of pathogenic fungi. This finding has potential implications in antifungal therapy.

Two-dimensional gel electrophoresis as analytical tool for identifying Candida albicans immunogenic proteins

This paper reports the usefulness of two-dimensional gel electrophoresis followed by Western blotting with sera from patients with systemic candidiasis in the identification of the major Candida albicans antigens. In order to have different patterns of protein expression and subcellular localization, three types of protein preparations were obtained: cytoplasmic extracts, protoplast lysates and proteins secreted by protoplasts regenerating their cell wall. These proteins were separated by high-resolution two-dimensional electrophoresis using an immobilized pH gradient. Western blotting with sera from patients with systemic candidiasis allowed the detection of more than 18 immunoreactive proteins. Some of these proteins had different isoforms. All sera reacted with at least three C. albicans proteins and the most reactive serum detected up to eleven proteins. Some of these antigens, e.g., enolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), have been identified on the 2-D map. The most reactive proteins were enolase and a 34 kDa protein in the acidic part of the gel (pI 4-4.4) that was only detected in regenerating protoplast-secreted proteins. The identification of all these antigens would be useful for the development of diagnostic strategies.

Two-dimensional analysis of proteins secreted by Saccharomyces cerevisiae regenerating protoplasts: a novel approach to study the cell wall

Protoplasts of Saccharomyces cerevisiae incubated in regenerating conditions secrete cell wall components in order to allow the biosynthesis of this structure. During the first hours of incubation, many of these are not retained in the forming cell wall but remain in the medium. We have developed a method for collecting the secreted proteins and have analysed these by two-dimensional electrophoresis to obtain a reference map of putative cell wall proteins. Several proteins were identified by microsequencing or immunoblotting; namely, cell wall hydrolytic enzymes, heat shock proteins, glycolytic enzymes and others. Some beta-1,3- and beta-1, 6-glucosylation was detected in the proteins secreted by regenerating protoplasts.

Cloning and sequence of a 3.835 kbp DNA fragment containing the HIS4 gene and a fragment of a PEX5-like gene from Candida albicans

We have isolated the Candida albicans HIS4 (CaHIS4) gene by complementation of a his4-34 Saccharomyces cerevisiae mutant. The sequenced DNA fragment contains a putative ORF of 2514 bp, whose translation product shares a global identity of 44% and 55% to the His4 protein homologs of S. cerevisiae and Kluyveromyces lactis, respectively. Analysis of CaHIS4 sequence suggests that, similarly to S. cerevisiae HIS4, it codes for a polypeptide having three separate enzymatic activities (phosphoribosyl-AMP cyclohydrolase, phosphoribosyl-ATP pyrophosphohydrolase and histidinol dehydrogenase) which reside in different domains of the protein. A C. albicans his4 strain is complemented with this gene when using a C. albicans-S. cerevisiae-Escherichia coli shuttle vector, thus enabling the construction of a host system for C. albicans genetic manipulation. In addition, upstream of the sequenced CaHIS4 sequence, we have found the 3'-terminal half of a gene encoding a PEX5-like protein.

Candida albicans: genetics, dimorphism and pathogenicity

Candida albicans is a dimorphic fungus that causes severe opportunistic infections in humans. Recent advances in molecular biology techniques applied to this organism (transformation systems, gene disruption strategies, new reporter systems, regulatable promoters) allow a better knowledge of both the molecular basis of dimorphism and the role of specific genes in Candida morphogenesis. These same molecular approaches together with the development of appropriate experimental animal models to analyze the virulence of particular mutants, may help to understand the molecular basis of Candida virulence.

Induced expression of the Candida albicans multidrug resistance gene CDR1 in response to fluconazole and other antifungals

The Candida albicans CDR1 gene encodes a member of the ABC-type family of multidrug transporters which has been shown to be involved in azole resistance. Using an in-frame gene fusion between the CDR1 open reading frame and the green fluorescent protein allele yEGFP3, an optimized derivative for its use in C. albicans, we show here how the CDR1-yEGFP3 gene expression is induced in response to azoles as well as to other structurally unrelated drugs like cycloheximide. Moderate increases were observed for calcofluor, canavanine, 5'-fluorcytosine, cilofungin and caffeine, while no induction was found for the antifungals benomyl and amphotericin B or hydrogen peroxide at subinhibitory concentrations. The use of confocal microscopy enabled us to localize the Cdr1p fusion protein at the cell periphery, thus suggesting a cytoplasmic membrane localization. These results suggest deregulation of CDR1 gene as a putative mechanism for the generation of azole resistance in this clinically important pathogenic fungus.

[Molecular and genetic aspects of resistance to azoles in Candida albicans]

Fluconazole is one of the most useful drugs in the treatment of fungal systemic infections which frequently affect non immunocompetent individuals. However, the emergence of resistant strains in recent years may severely limit its usefulness in future. Although there are several described mechanisms involved in resistance to azoles, recent genetic studies demonstrate the role of specific genes in clinical resistance. Currently, the best characterized are the MDR1 and CDR1 genes, which code members of the MFS or ABC family of drug transporters, respectively. These proteins respond to the membrane potential (MFS) or hydrolyse ATP (ABC) thus promoting drug efflux and therefore reducing its intracellular accumulation. It has been shown that the mRNA from these genes is frequently increased in some Candida albicans resistant strains from patients receiving long term azole treatment. The development of molecular genetic tools in C. albicans is allowing characterization of their role in this and other important processes in the fungal cell.

Cloning, analysis and one-step disruption of the ARG5,6 gene of Candida albicans

The ARG5,6 gene from the dimorphic fungus Candida albicans was cloned by functional complementation of the arginine auxotrophy present in strain EL2 (Arg-) using a gene library constructed in the double autonomously replicating sequence vector pRM1. Sequence analysis revealed a putative 857 amino acid polypeptide (95 kDa) which showed high homology (63% protein identity) to the Saccharomyces cerevisiae ARG5,6 gene. Similarly to the S. cerevisiae gene, the C. albicans ARG5,6 gene is responsible for both the acetylglutamate kinase and acetylglutamyl-phosphate reductase activities, the second and third steps of arginine biosynthesis at the mitochondria. The C. albicans ARG5,6 gene complemented the arg6 mutation present in S. cerevisiae (strain D160-4D) on a yeast episomal plasmid using its own regulatory signals. A set of non-integrative high-efficiency plasmid vectors based on this gene marker was constructed and a null C. albicans arg5,6 delta strain was obtained using the common URA3-blaster strategy. In addition, we generated an arg5,6 delta null mutant in a single transformation event, thus improving the basic strategy for generating gene deletions in C. albicans.

Reduced virulence of Candida albicans MKC1 mutants: a role for mitogen-activated protein kinase in pathogenesis

Deletion of the Candida albicans mitogen-activated protein kinase MKC1 gene gave rise to viable cells whose cell integrity was affected (F. Navarro-García, M. Sánchez, J. Pla, and C. Nombela, Mol. Cell. Biol. 15:2197-2206, 1995). In an experimental infection system using a murine model, the C. albicans mkc1 delta/mkc1 delta strain was found to be less pathogenic than the parental strain, as show the different time of survival, percentage of mortality, fungal load in the most representative organs, and histological analysis. This is the first study that shows the involvement of the cell integrity pathway in the pathogenicity of a dimorphic fungus.

Anal carcinoma: a 14 year experience

A retrospective analysis of 20 patients with anal carcinoma treated at Hospital del Mar (Barcelona) from 1982 to 1995 was performed to evaluate clinical and pathological characteristics. This subset represents 2.1% of all the colon and rectum cancers registered in the same period. The mean age was 74 years (42-92), the female to male ratio was 1.5:1. The most frequent site was anal canal (80%) and the histological type was squamous cell and basaloid carcinomas in all cases. Five aged patients were not treated. Twelve patients were primary treated by abdominal perineal resection, 2 patients by radiotherapy and one by a local excision. The prognosis of 8 patients treated with palliative surgery was poor and none survived 30 months after surgery. In contrast, 4 of 5 patients are alive after radical surgery with a minimum 5 year follow-up. Two patients treated with radiotherapy are disease free at 7 and 13 months after treatment. The incidence of anal carcinoma is low, but our experience shows that it is diagnosed at an advanced stage and surgery is not always successful. Radiotherapy with or without chemotherapy, is an effective alternative.

The mitogen-activated protein kinase homolog HOG1 gene controls glycerol accumulation in the pathogenic fungus Candida albicans

The Candida albicans HOG1 gene (HOG1CA) was cloned by functional complementation of the osmosensitive phenotype associated with Saccharomyces cerevisiae hog1 delta mutants. HOG1CA codes for a 377-amino-acid protein, 78% identical to S. cerevisiae Hog1p. A C. albicans hog1 null mutant was found to be sensitive to osmotic stress and failed to accumulate glycerol on high-osmolarity media.

Cloning of Candida albicans SEC14 gene homologue coding for a putative essential function

The yeast SEC14 gene product is required for the transport of proteins from the Golgi complex. We have cloned the homologous Candida albicans SEC14 gene (CaSEC14) by functional complementation of a Saccharomyces cerevisiae thermosensitive mutant, sec14ts. Some putative TATA boxes have been identified in CaSEC14 and, contrary to S. cerevisiae SEC14, no introns were found in the Candida homologue. Sequence analysis revealed that CaSec14p is a 301 amino acid protein, 67% identical to S. cerevisiae and Kluyveromyces iactis Sec14p, and 61% identical to the 300 amino-terminal residues of Yarrowia lipolytica Sec14p. Hydrophatic profile analysis of CaSec14p suggests a soluble protein without transmembrane domains as has been described for the S. cerevisiae counterpart. While it was easy to disrupt one allele of SEC14 in C. albicans, repeated attempts to disrupt the second allele were unsuccessful, thus suggesting that the gene could be essential for vegetative growth in C. albicans.

Cloning of the Candida albicans HIS1 gene by direct complementation of a C. albicans histidine auxotroph using an improved double-ARS shuttle vector

ARS2 and ARS3 are two Candida albicans (Ca) DNA fragments with autonomous replicating activity that have been shown to promote non-integrative genetic transformation of both Ca and Saccharomyces cerevisiae (Sc). We have developed several shuttle vectors based on either ARS fragment, or the combination of both, and using the CaURA3 gene as a selection marker. The combination of ARS2 and ARS3 fragments in a single vector did not increase transformation frequencies but improved the stability of transformant plasmids in Ca cells, so that the degree of intracellular recombination was reduced. A Ca genomic DNA library was constructed on the double-ARS vector, pRM1, to be used for direct cloning in Ca by complementation of the histidine auxotrophy of strain CA9. By screening this library, we cloned CaHIS1, the Ca gene that encodes ATP phosphoribosyl transferase, one of the enzymes that participates in histidine biosynthesis. The deduced protein, CaHis1p, is 60.6% identical (73% similar) to ScHis1p (EC 2.4.2.17). The cloned gene is the first auxotrophic gene marker mapped to fragment I of chromosome 5 in the standard Ca genetic map. Our results represent the first demonstration of a direct cloning system in the opportunistic fungus Ca that does not require the use of an intermediate host such as Sc for plasmid rescue. This system could be used for the isolation of any gene affected in Ca mutants displaying a selectable or identifiable phenotype.

Chromosome reorganization in Candida albicans 1001 strain

The karotype of Candida albicans 1001, a pathogenic isolate, presents two additional chromosome bands when compared with C. albicans 1006 strain. These two bands were a 2600 kb chromosome located between chromosome group 1-R and chromosome 2 (named chromosome 2*) and a 710 kb small chromosome, called snc due to its similarity in size to the supernumerary chromosome in strain WO-1. A comparison of karyotypes of strains 1001, 1006 and WO-1 has enabled us to conclude that chromosomes 2 and 7 are involved in such a reorganization giving rise to the new chromosome bands of strain 1001. We describe a tentative physical map of C. albicans 1001 based on the previously outlined map of C. albicans strain 1006.

Functional characterization of the MKC1 gene of Candida albicans, which encodes a mitogen-activated protein kinase homolog related to cell integrity

Mitogen-activated protein (MAP) kinases represent a group of serine/threonine protein kinases playing a central role in signal transduction processes in eukaryotic cells. Using a strategy based on the complementation of the thermosensitive autolytic phenotype of slt2 null mutants, we have isolated a Candida albicans homolog of Saccharomyces cerevisiae MAP kinase gene SLT2 (MPK1), which is involved in the recently outlined PKC1-controlled signalling pathway. The isolated gene, named MKC1 (MAP kinase from C. albicans), coded for a putative protein, Mkc1p, of 58,320 Da that displayed all the characteristic domains of MAP kinases and was 55% identical to S. cerevisiae Slt2p (Mpk1p). The MKC1 gene was deleted in a diploid Candida strain, and heterozygous and homozygous strains, in both Ura+ and Ura- backgrounds, were obtained to facilitate the analysis of the function of the gene. Deletion of the two alleles of the MKC1 gene gave rise to viable cells that grew at 28 and 37 degrees C but, nevertheless, displayed a variety of phenotypic traits under more stringent conditions. These included a low growth yield and a loss of viability in cultures grown at 42 degrees C, a high sensitivity to thermal shocks at 55 degrees C, an enhanced susceptibility to caffeine that was osmotically remediable, and the formation of a weak cell wall with a very low resistance to complex lytic enzyme preparations. The analysis of the functions downstream of the MKC1 gene should contribute to understanding of the connection of growth and morphogenesis in pathogenic fungi.

Expression and in vivo determination of firefly luciferase as gene reporter in Saccharomyces cerevisiae

The LUC gene coding for Photinus pyralis firefly luciferase was cloned in different yeast episomal plasmids in order to assess its possibilities as an in vivo reporter gene. Activity of the enzyme in transformed cells in vivo was measured by following light emission and assay conditions optimized in intact cells, with regard to oxygen concentration, temperature, cell concentration in assay mixtures and external ATP concentration. Among the factors tested, light emission was drastically influenced by the external pH in the assay (which resulted in a ten-fold amplification signal) and by substrate permeability. The growth phase of the cells was also important for the level of activity detected. Cloning of firefly luciferase gene under the control of different yeast-regulated promoters (ADH1, GAL1-10) enabled us to measure their strength which correlated well with previously described data. We conclude that firefly luciferase is an adequate gene reporter for the in vivo sensitive determination of gene expression and promoter strength in yeast.

Characterisation of mutant alleles of the cell division protein FtsA, a regulator and structural component of the Escherichia coli septator

Two alleles of ftsA, a gene that encodes an essential cell division protein in Escherichia coli, have-been mapped at the nucleotide level. The mutations are located inside domains that are conserved in an ATP-binding protein family. The ftsA2 mutation lies in the adenine-binding domain, and the ftsA3 in the ribose-binding domain. The defect in ampicillin binding to PBP3 described for allele ftsA3 is allele-specific. This supports the hypothesis of the existence of different domains in FtsA having different functions.

An amino-proximal domain required for the localization of FtsQ in the cytoplasmic membrane, and for its biological function in Escherichia coli

The location of FtsQ, an Escherichia coli protein essential for cell division, is, under physiological conditions, in the cytoplasmic membrane facing towards the periplasmic space. An amino-proximal hydrophobic domain is required for FtsQ to reach its location and for its activity in the cell. Overexpression of modified forms of FtsQ is deleterious for the cell.

Preferential cytoplasmic location of FtsZ, a protein essential for Escherichia coli septation

An ftsZ thermonull mutant has been constructed in which the ftsZ gene has been deleted from the Escherichia coli chromosome while maintaining a wild-type copy of the gene in a thermosensitive plasmid. Under conditions in which the ftsZ+ allele is unable to be replicated at the same pace as the chromosome, the cells become non-viable and grow as filaments, indicating that, contrary to other reports, FtsZ performs a function essential for cell survival. Antibodies raised against FtsZ have been used to detect the cellular location of FtsZ and its contents per cell. Fractionation experiments indicate that most of the total FtsZ present in the cell stays in the cytoplasm.

On the chronology and topography of bacterial cell division

Gene products that play a role in the formation of cell septum should be expected to be endowed with a set of specific properties. In principle, septal proteins should be located at the cell envelope. The expression of division genes should ensure the synthesis of septal proteins at levels commensurate with the needs of cell division at different rates of cell duplication. We have results indicating that some fts genes located within the 2.5-min cluster in the Escherichia coli chromosome conform to these predictions.

Division genes in Escherichia coli are expressed coordinately to cell septum requirements by gearbox promoters

The cell division ftsQAZ cluster and the ftsZ-dependent bolA morphogene of Escherichia coli are found to be driven by gearboxes, a distinct class of promoters characterized by showing an activity that is inversely dependent on growth rate. These promoters contain specific sequences upstream from the mRNA start point, and their -10 region is essential for the inverse growth rate dependence. Gearbox promoters are essential for driving ftsQAZ and bolA gene expression so that the encoded products are synthesized at constant amounts per cell independently of cell size. This mode of regulation would be expected for the expression of proteins that either play a regulatory role in cell division or form a stoichiometric component of the septum, a structure that, independently of cell size and growth rate, is produced once per cell cycle.

The native form of FtsA, a septal protein of Escherichia coli, is located in the cytoplasmic membrane

Antisera able to recognize FtsA, one of the septal proteins of Escherichia coli, have been obtained and used to show that native FtsA, when expressed at levels ranging from physiological to induced from lambda pR, is located in the inner membrane. Experiments of trypsin accessibility to FtsA in membranes, spheroplasts, and vesicles indicated that FtsA is located such that it faces the cytoplasm. This location is consistent with current knowledge about the participation of FtsA in a molecular complex active in cell division called septator.

A new beta-lactam-binding protein derived from penicillin-binding protein 3 of Escherichia coli

In this paper we describe a new beta-lactam-binding protein from the cell envelope of Escherichia coli. It can be detected in cells grown at either 37 or 42 degrees C in medium containing glucose but not in cells grown at 30 degrees C. This novel component has an apparent molecular size that is 2.0 kilodaltons larger than that of penicillin-binding protein 3 and is derived from the latter through a divalent-cation-mediated process probably catalyzed by components located in the periplasmic space. The significance of this protein with regard to regulation of the amount of functional penicillin-binding protein 3 in the cell is discussed.

Perforation of colonic neoplasms. A review of 36 cases

Colonic perforation is the second most common complication of colonic neoplasms and is associated with an elevated morbidity and mortality. We undertook a two-centre retrospective analysis of 378 colonic neoplasms seen from 1978 to 1985. Thirty-six patients (9.5%) presented with a perforated colonic carcinoma. Two-thirds had a past history suggesting colonic disease while in the remaining one-third, the perforation was the first manifestation of the disease. Resection was carried out initially in 33 cases (21 Hartmann's procedure, 9 primary anastomosis, 2 mucous fistula and 1 abdominoperineal excision). Two patients had a proximal colostomy only and 1 an exploratory laparotomy only because of disseminated disease. Postoperative mortality was 14% (five cases). Actuarial survival rate was 52% at 1 year and 40% at 2 years. Eleven patients are still alive after a mean follow-up of 43 months.