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At least 1,423 records · Page 79Linked to original sources
PubMed2003

Diversity of L-leucine catabolism in various microorganisms involved in dairy fermentations, and identification of the rate-controlling step in the formation of the potent flavour component 3-methylbutanal.

Various microorganisms, belonging to the genera Lactococcus, Lactobacillus, Streptococcus, Leuconostoc, Bifidobacterium, Propionibacterium, Brevibacterium, Corynebacterium and Arthrobacter, used in dairy fermentations such as cheese making, were analysed for their potential to convert leucine into flavour components, most notably 3-methylbutanal. A large variation between and within species was observed for various enzyme activities involved in the conversion pathway, e.g. transaminases, alpha-hydroxy acid dehydrogenase and alpha-keto acid decarboxylase. In particular, alpha-keto acid decarboxylase activity-leading to 3-methylbutanal-was found to be present in only two of the strains tested. It is proposed that this activity is rate-controlling in the conversion pathway leading to the flavour compound 3-methylbutanal.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed2004

HBMMD: an enhanced database of the microorganisms associated with deeper water marine invertebrates.

The Harbor Branch Marine Microbial Database (HBMMD) provides preliminary taxonomic identifications and features of microorganisms maintained in the Harbor Branch Oceanographic Institution Marine Microbial Culture Collection. The microbes are primarily derived from marine invertebrates such as sponges (phylum Porifera) and soft corals (phylum Cnidaria) found in deep water environments [>120 feet (>35 m) seawater]. The microbes isolated from within marine invertebrates represent some unique taxa and phylogenetic signatures. The database provides a user-friendly method to systemically search or sort a desired input. The site allows a powerful search for multiple parameters of any entry. Images of the microbes are contained within the database and can be accessed from the website. The HBMMD homepage is located at http://www.hboi.edu/dbmr/dbmr_hbmmd.html.

Animals↗
PubMed2005

Global physiological understanding and metabolic engineering of microorganisms based on omics studies.

Through metabolic engineering, scientists seek to modify the metabolic pathways of living organisms to facilitate optimized, efficient production of target biomolecules. During the past decade, we have seen notable improvements in biotechnology, many of which have been based on metabolically engineered microorganisms. Recent developments in the fields of functional genomics, transcriptomics, proteomics, and metabolomics have changed metabolic engineering strategies from the local pathway level to the whole system level. This article focuses on recent advances in the field of metabolic engineering, which have been powered by the combined approaches of the various "omics" that allow us to understand the microbial metabolism at a global scale and to develop more effectively redesigned metabolic pathways for the enhanced production of target bioproducts.

Biomedical Engineering↗
PubMed2006

Integrating metabolomics into a systems biology framework to exploit metabolic complexity: strategies and applications in microorganisms.

As an important functional genomic tool, metabolomics has been illustrated in detail in recent years, especially in plant science. However, the microbial category also has the potential to benefit from integration of metabolomics into system frameworks. In this article, we first examine the concepts and brief history of metabolomics. Next, we summarize metabolomic research processes and analytical platforms in strain improvements. The application cases of metabolomics in microorganisms answer what the metabolomics can do in strain improvements. The position of metabolomics in this systems biology framework and the real cases of integrating metabolomics into a system framework to explore the microbial metabolic complexity are also illustrated in this paper.

Bacteria↗
PubMed2000

Inhibition of the development of microorganisms (bacteria and fungi) by extracts of marine algae from Brittany, France.

The inhibitory effects of aqueous, ethanolic and dichloromethane fractions from 16 marine algae from the Atlantic shores of North-East Brittany, France, have been investigated against microorganisms frequently associated with immersed surfaces. The extracts were tested in vitro against isolates of marine fungi, bacteria and yeasts potentially involved at different stages in the formation of biofilms in the sea. The high levels of inhibitory activity of nine extracts against marine fungi and Gram-positive bacteria and their apparent absence of toxicity against larvae of oysters and sea urchins suggests a potential for novel active ingredients.

Animals↗
PubMed1997

Biodegradation of the pesticide 4,6-dinitro-ortho-cresol by microorganisms in batch cultures and in fixed-bed column reactors.

A mixed culture of microorganisms able to utilize 4,6-dinitro-ortho-cresol (DNOC) as the sole source of carbon, nitrogen and energy was isolated from soil contaminated with pesticides and from activated sludge. DNOC was decomposed aerobically in batch cultures as well as in fixed-bed column reactors. Between 65% and 84% of the substrate nitrogen was released as nitrate into the medium, and 61% of the carbon from uniformly 14C-labelled DNOC was recovered as 14CO2. The mixed microbial culture also decomposed 4-nitrophenol and 2,4-dinitrophenol but not 2,3-dinitrophenol, 2,6-dinitrophenol, 2,4-dinitrotoluene, 2,4-dinitrobenzoic acid or 2-sec-butyl-4,6-dinitrophenol (Dinoseb). Maximal degradation rates for DNOC by the bacterial biofilm immobilized on glass beads in fixed-bed column reactors were 30 mmol day-1 (1 reactor volume)-1, leaving an effluent concentration of less than 5 micrograms l-1 DNOC in the outflowing medium. The apparent Ks value of the immobilized mixed culture for DNOC was 17 microM. Degradation was inhibited at DNOC concentrations above 30 microM and it ceased at 340 microM, possibly because of the uncoupling action of the nitroaromatic compound on the cellular energy-transducing mechanism.

2,4-Dinitrophenol↗
PubMed1998

Degradation of dioxin-like compounds by microorganisms.

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF; PCDD/F, dioxins) have not been commercially produced in bulk amounts, as were polychlorinated biphenyls and other haloaromatic organics. Within the past two decades a lot of information has accumulated on the biodegradation of PCDD/F and other dioxin-like compounds because of their toxicity and because of significant environmental concern about many congeners of this class of chemicals. PCDD/F are subjected to reductive dehalogenations leading to less halogenated congeners, which can be attacked efficiently by fungal and bacterial oxidases and dioxygenases. In several cases these compounds can be utilized as carbon and energy sources. Pathways for their enzymatic degradation and the organisation of the corresponding degradative genes have been elucidated. Consequently, biotechnological applications will exploit the degradative potential of such microorganisms for bioremediation of contaminated sites.

Bacteria↗
PubMed1998

Microorganism inactivation using high-pressure generation in sealed vessels under sub-zero temperature.

In order to test the possibility of utilizing high pressure in bioscience and biotechnology, a simple method for high-pressure generation and its use for microbial inactivation have been studied. When a pressure vessel was filled with water, sealed tightly and cooled to sub-zero temperatures, high pressure was generated in the vessel. The pressure generation was 60 MPa at -5 degrees C, 103 MPa at -10 degrees C, and 140 MPa at -15 degrees C, -20 degrees C, and -22 degrees C. The high pressure generated inactivated microorganisms effectively: yeasts (Saccharomyces cerevisiae and Zygosaccharomyces rouxii), bacteria (Lactobacillus brevis and Eschericia coli), and fungi (Aspergillus niger and Aspergillus oryzae) were completely inactivated when stored in sealed vessels -20 degrees C for 24 h. However, Staphylococcus aureus was only partly inactivated under the same conditions. This method opens up a new application of high pressure for storing, transporting, and sterilizing of foods and biological materials.

Bacteria↗
PubMed1999

Containment of a genetically engineered microorganism during a field bioremediation application.

A field release of a genetically engineered microorganism was performed at the Field Lysimeter Site on the Oak Ridge Reservation. Six large lysimeters were filled with soil that had been contaminated with a mixture of naphthalene, phenanthrene, and anthracene. A genetically engineered bacterial strain, Pseudomonas fluorescens HK44, was sprayed onto the surface of the soil during soil loading. This strain contains a fusion between the lux genes of Vibrio fischeri and the promoter for the lower pathway of naphthalene degradation, enabling the strain to become bioluminescent when it is degrading naphthalene. Release of the bacteria outside the lysimeters was monitored, using selective agar plates and one-stage Anderson air samplers. Although approximately 10(14) bacteria were sprayed during the loading process, escape was only detected sporadically; the highest incidence of bacterial escape was found when the relative humidity and wind speed were low.

Air Microbiology↗
PubMed1999

High-cell-density cultivation of microorganisms.

High-cell-density cultivation (HCDC) is required to improve microbial biomass and product formation substantially. An overview of HCDC is given for microorganisms including bacteria, archae and eukarya (yeasts). Problems encountered by HCDC and their possible solutions are discussed. Improvements of strains, different types of bioreactors and cultivation strategies for successful HCDC are described. Stirred-tank reactors with and without cell retention, a dialysis-membrane reactor, a gas-lift reactor and a membrane cyclone reactor used for HCDC are outlined. Recently modified traditional feeding strategies and new ones are included, in particular those for unlimited growth to very dense cultures. Emphasis is placed on robust fermentation control because of the growing industrial interest in this field. Therefore, developments in the application of multivariate statistical control, artificial neural networks, fuzzy control and knowledge-based supervision (expert systems) are summarized. Recent advances using Escherichia coli--the pioneer organism for HCDC--are outlined.

Archaea↗
PubMed2001

Influence of the fluidity of the membrane on the response of microorganisms to environmental stresses.

The aim of this mini-review is to relate membrane physical properties to the adaptation and resistance of microorganisms to environmental stresses. In the first part, the effects of various stresses on the structure and dynamic properties of phospholipid and biological membranes are presented. The compensation of these effects, i.e., change in membrane fluidity, phase transitions, by the active cellular control of the membrane chemical composition, is then described. In this natural process, the change in membrane fluidity is viewed as the detecting "input" signal that initiates the regulation, activating proteic effectors that in turn may influence the chemical composition of the membrane (feedback). This adaptation system allows the maintenance of the physical characteristics of membranes and, thereby, of their functionality. When environmental stresses are extreme and occur abruptly, the regulation process may not compensate for the changes in the membrane physical characteristics. In such cases, important variations in the membrane fluidity and structure may induce cellular damages and cell death. However, the lethal consequences are not systematically observed because protective effects of changes in the membrane physical state on the resistance to stresses are also reported.

Membrane Fluidity↗
PubMed2001

Numerical taxonomy of microorganisms isolated from goat cheese made in Chile.

118 strains of heterotrophic microorganisms were isolated from goat cheese produced domestically in the IV Region of Northern Chile (Serene, Ovalle, and Illapel) and sold in supermarkets in Valparaíso, Chile. The results of 89 phenotypic tests were numerically analyzed against 17 reference strains, using the simple matching coefficient (S(SM)). Thirteen phena were found at a 78% similarity level. Five of them (A, B, C, D, and E) were assigned to the family Enterobacteriaceae, phenon F was identified as belonging to the genus Aeromonas and strains of phenon G were assigned to the genus Acinetobacter. The other phena were identified as being members of the genera Bacillus (H, I, and J), Staphylococcus (K), Enterococcus (L), and Micrococcus (M). Approximately 19% of the isolates were Escherichia coli and 27%, Staphylococcus aureus.

Animals↗
PubMed2000

News & notes: detection of microorganisms with overall cellulolytic activity.

A modification is described of the plate method for the detection of microorganisms with overall cellulolytic activity, including those like Cytophaga, in which the activity is cell bound. Within a few days of incubation colonies of cellulose-degrading bacteria formed holes in discs of lens paper placed on freshly inoculated agar plates.

Actinomycetales↗
PubMed2002

Expression of xylanase enzymes from thermophilic microorganisms in fungal hosts.

Bulk production of xylanases from thermophilic microorganisms is a prerequisite for their use in industrial processes. As effective secretors of gene products, fungal expression systems provide a promising, industrially relevant alternative to bacteria for heterologous enzyme production. We are currently developing the yeast Kluyveromyces lactis and the filamentous fungus Trichoderma reesei for the extracellular production of thermophilic enzymes for the pulp and paper industry. The K. lactis system has been tested with two thermophilic xylanases and secretes gram amounts of largely pure xylanase A from Dictyoglomus thermophilum in chemostat culture. The T. reesei expression system involves the use of the cellobiohydrolase I (CBHI) promoter and gene fusions for the secretion of heterologous thermostable xylanases of both bacterial and fungal origin. We have reconstructed the AT-rich xynB gene of Dictyoglomus thermophilum according to Trichoderma codon preferences and demonstrated a dramatic increase in expression. A heterologous fungal gene, Humicola grisea xyn2, could be expressed without codon modification. Initial amounts of the XYN2 protein were of a gram per liter range in shake-flask cultivations, and the gene product was correctly processed by the heterologous host. Comparison of the expression of three thermophilic heterologous microbial xylanases in T. reesei demonstrates the need for addressing each case individually.

Amino Acid Sequence↗
PubMed2003

A novel lineage of sulfate-reducing microorganisms: Thermodesulfobiaceae fam. nov., Thermodesulfobium narugense, gen. nov., sp. nov., a new thermophilic isolate from a hot spring.

A novel type of a sulfate-reducing microorganism, represented by strain Na82T, was isolated from a hot spring in Narugo, Japan. The isolate was a moderate thermophilic autotroph that was able to grow on H2/CO2 by sulfate respiration. The isolate could grow with nitrate in place of sulfate, and possessed menaquinone-7 and menaquinone-7(H2) as respiratory quinones. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Na82T was a member of the domain Bacteria and distant from any known bacteria, as well as from other sulfate-reducing bacteria (sequence similarities less than 80%). The phylogenetic analysis of the dsrAB gene (alpha and beta subunits of dissimilatory sulfite reductase) sequence also suggested that strain Na82T was not closely related to other sulfate reducers. On the basis of the phenotypic and phylogenetic data, a new taxon is established for the isolate. We proposed the name Thermodesulfobium narugense gen. nov., sp. nov. with strain Na82T (=DSM 14796T=JCM 11510T) as the type strain. Furthermore, a new family, Thermodesulfobiaceae fam. nov., is proposed for the genus.

Animals↗
PubMed2002

Do HIV-seropositive patients become colonised with drug-resistant microorganisms?

The aim of the present study was to investigate whether HIV-infected patients, a group that is supposedly at risk for infection with antibiotic-resistant microbes, really does so, and to assess possible risk factors for acquiring these organisms. During the period from January 1998 to July 1999, samples of normal flora were obtained from 107 HIV-infected patients attending an outpatient clinic in Oslo, Norway. The samples were cultured for Streptococcus pneumoniae, Haemophilus influenzae, Escherichia coli, coagulase-negative staphylococci and Candida spp., and the resulting isolates were tested for antimicrobial susceptibility. The patients studied represented all stages of HIV infection, from recently infected to severely immunocompromised. Samples were taken at one, two or three time-points to determine whether antimicrobial resistance in colonising microorganisms increases over time. Antimicrobial resistance was linked primarily to antimicrobial prophylaxis, but it did not increase during the observation period. The level of a patient's immunodeficiency and the consequently intensified medical care was also of some importance. Even though about 50% of the patients were receiving antimicrobial agents at the time of sampling, the level of resistance found in these patients was very similar to that found in other patient groups in Norway; except for Candida albicans isolates, which were less susceptible to fluconazole. Overall, antimicrobial resistance was uncommon in the HIV-seropositive patients studied, a finding that is probably related to the overall low prevalence of antimicrobial resistance in the general population in Norway.

Adult↗
PubMed2006

Cold-adapted enzymes from marine Antarctic microorganisms.

The Antarctic marine environment is characterized by challenging conditions for the survival of native microorganisms. Indeed, next to the temperature effect represented by the Arrhenius law, the viscosity of the medium, which is also significantly enhanced by low temperatures, contributes to slow down reaction rates. This review analyses the different challenges and focuses on a key element of life at low temperatures: cold-adapted enzymes. The molecular characteristics of these enzymes are discussed as well as the adaptation strategies which can be inferred from the comparison of their properties and three-dimensional structures with those of their mesophilic counterparts. As these enzymes display a high specific activity at low and moderate temperatures associated with a relatively high thermosensitivity, the interest in these properties is discussed with regard to their current and possible applications in biotechnology.

Adaptation, Physiological↗