Showing papers in "Annals of Microbiology in 2000"

Bifidobacteria: history, ecology, physiology and applications.

Abstract: The review considers the following aspects: the milestones in Bifidobacterium history from their discovery to the new hierarchical structure collecting the genus Bifidobacterium with the genus Gardnerella into the family of Bifidobacteriaceae in the order of Bifidobacteriales; their ecology in human, animals and in extrabody habitats; the identification approaches at genus, species and strain level; the optimum temperature and pH, sensitivity to oxygen, hexose metabolisms, cell wall structure, antagonistic activity, susceptibility to antibiotics, nutritional requirements and the importance of bifidobacteria as probiotics microorganisms.

Selection and improvement of wine yeasts

Abstract: The selection of wine yeasts is usually carried out within the species Saccha- romyces cerevisiae. It aims at identifying the yeast strains that, besides fermenting grape juice vigorously and producing high ethanol yield, can also positively influence the com- position and the sensorial characteristics of wine. The natural availability of yeast strains possessing an ideal combination of oenological characteristics is highly improbable. Moreover, selected S. cerevisiae wine strains usually produce wines with a plain aromatic profile. The extension of the selection of wine yeasts to S. cerevisiae not growing in oeno- logical environments or to non-Saccharomyces yeasts has provided strains possessing novel and interesting oenological characteristics. Nevertheless, these strains cannot be directly used as starter cultures in wine fermentations, mainly because they are not vigo- rous or competitive in oenological conditions. Wine strains possessing innovative oenolo- gical traits that can influence the sensorial characteristics of wine can be constructed using genetic or molecular methods. Intraspecific S. cerevisiae hybridisation has provided useful oenological strains. Nevertheless, the traits of oenological interest that can be exchanged or introduced using this technique are only those commonly found in the species S. cerevisiae. Innovative oenological traits can be introduced or exchanged by hybridising strains belon- ging to different species but with a sufficient genetic affinity for them to mate. Interspeci- fic Saccharomyces hybrids were found to be stable, vigorous and possessing the parental oenological traits in novel and interesting combinations. Nevertheless, they are sterile; the genetic improvement cannot therefore be taken further than the first generation. Moreover, the combination of the parental traits cannot be specifically programmed and a combina- tion of positive traits is often the result of chance. The recent development of recombinant DNA technology has overcome the limitations of traditional genetic techniques as well as broadening the potential of wine yeast improvement.

Isolation of endophytic fungi and Actinomycetes taxane producers.

Abstract: The fungal and actinomycete populations of internal tissues of woody branches, shoots and leaves of different plants belonging to the genus Taxus were investigated. 22 plants of Taxus baccata and one of Taxus brevifolia were sampled in different habitats located in central-northern Italy. 150 fungal and 71 actinomycete strains were isolated, some of them from woody tissues, others from herbaceous ones. Both microbial populations are composed of representatives of different genera and for the first time the presence of actinomycetes inside living tissues of plant above-ground organs is reported. Fungi and actinomycetes were screened for taxane production. Different liquid media were used for strain growth and the culture extracts were assayed by a competitive inhibition enzyme immunoassay (CIEIA) using a commercial kit employing a polyclonal antibody. The production of taxanes was detected in 15 out of 150 fungal strains and in 10 out of 71 actinomycetes, isolated both from woody and herbaceous tissues. In both populations, the production of taxanes was quantitatively low and only in few cases reached the 50-100 ng per litre. The capability to produce taxanes seems not to be related to the geographical origin of isolation sources of the fungal taxon but with a particular tree from which the fungus was isolates.

Selenite tolerance and accumulation in the Lactobacillus species

Abstract: - The effect of selenium as selenite (Se 4+ ) on cell growth and accumulation in the Lactobacillus species was investigated in batch cultures using Se 4+ supplemented MRSbroth. All the strains, except two, Lactobacillus rhamnosus LB3 and Lactobacillus fer-mentum LB7, for which a functional role of Se can be suggested, were inhibited by 1 mgl –1 of Se 4+ . Six tested Lactobacillus strains were able to concentrate selenium, though indifferent amounts. Most was membrane-bound, and was, in part, bound to -SH groups onthe external membrane surface. Selenium was also accumulated in the cytoplasm in boththe organic and the elemental form. The isolates were characterised by biochemical reac-tions and 16S rDNArestriction enzyme profiles and different species of Lactobacillus wereassigned on the basis of 16S rDNA sequences. Key words : Lactobacillus strains, 16S rDNARFLPs, Se specific accumulation, Se cellulardistribution. INTRODUCTION Selenium (Se) occurs in nature as selenite ion (Se

Studies on a strain of Kitasatospora sp. paclitaxel producer

Abstract: The strain P&U 22869, which produces paclitaxel and related taxanes, discovered during the course of endophytic actinomycetes screening on Taxus baccata plants, was classified as Kitasatospora sp. on the basis of its morphological characteristics observed by light and scanning electron microscopy, the presence of the major constituents of its cell wall and the 16S rDNA sequence. The morphophysiological profile of the strain was compared with those of the valid and invalid species described for this genus. The paclitaxel production detected by means of monoclonal antibody assay (CIEA) was confirmed by LC-MS analysis and its concentration determined by HPLC. The de novo paclitaxel biosynthesis operated by strain P&U 22869 was demonstrated by biosynthesis experiments with labeled precursors.

Ecological implications of synergistic and antagonistic interactions among growth and non growth analogs present in mixture.

Abstract: The degradation of an organic compound can be differently affected in the presence of a cosubstrate, often structurally related to the growth substrate. These effects, either synergistic or antagonistic, may be ascribed to different causes such as: the broad specificity of the catabolic enzymes, interferences in the enzymatic induction, catabolite repression mechanisms, competition at the active sites of the uptake enzymes, toxicity of the cosubstrates or of their dead-end products. As mixtures of contaminants may be present in the environment deriving from accidental release of petroleum hydrocarbons (BTEX and PAH S ), cometabolic degradation of polychlorinated biphenyls (chlorobenzoates), chlorina- tion of industrial effluents (chlorophenols, etc.), the occurrence of these effects can com- promise the decontamination strategies based on the activities of indigenous microorgan- isms (self-remediability) or of bacterial inocula (bioaugmentation). In this report, the inter- actions observed for mixtures of ecologically relevant compounds are summarised as well as the different causes to which such effects may be ascribed.

Survival of Lactobacillus acidophilus and Bifidobacterium infantis in yogurts manufactured from cowmilk and soymilk during storage at two temperatures.

Abstract: The survival of two microbial probiotics, Lactobacillus acidophilus and Bifi- dobacterium infantis, after inoculation into yogurts manufactured from cowmilk and soymilk during storage for 45 days at 4 and 12 °C was investigated. The sensory panel test carried out before the microbiological analyses showed that the flavour of soy yogurts made with cocoa powder or malt did not have the beany taste of soy beans. The survival of L. acidophilus in yogurts was significantly greater than the survival of B. infantis during storage at 4 and 12 °C. At 4 °C, the population remained between 107-108 CFU /ml for the former organism throughout the 45 day experiment. B. infantis reached a population of over 10 7 CFU /ml during the first 24 days at both temperatures but then it showed a marked decrease. The survival of B. infantis decreased substantially during storage at 12 o C, when no viable cells were found at day 31. In soy yogurts the survival of both probiotics was quite remarkable; B. infantis showed a significant increase of survival in plain- and flavoured-yogurts and more than 10 6 CFU/ml were detected in cocoa-flavoured yogurts after 38 days of storage.

The influence of human and animal visitation on the yeast ecology of three Italian caverns

Abstract: An ecological study of the yeast microflora of three caverns in Italy suggests that the quantity and types of species isolated are the result of outside pressures imposed upon these delicate ecosystems. One cavern, visited by 400,000 ca. visitors per year had the highest counts comprising also species pathogenic to humans.

Hydrolytic and synthetic activities of esterases and lipases of non-starter bacteria isolated from cheese surface.

Abstract: Bacteria of the genera Micrococcus, Brevibacterium and Staphylococcus isolated from the surface of the italian cheese Taleggio were grown in submerged cultures and checked for hydrolytic activity on agar plates using tributyrin, tricaprylin, triolein, Tween 20 and Tween 80 as current substrates showing general preference for short-chain esters The microorganisms showing the highest hydrolytic activity were lyophilized and employed in organic solvent for promoting the synthesis of different flavour esters (ethylbutyrate, butylacetate, ethylhexanoate, ethyloctanoate) starting from the alcohol and free acid with molar conversions ranging from 5 to 60%

Inheritance of mitochondrial DNA in interspecific Saccharomyces hybrids

Abstract: Spore conjugation between Saccharomyces cerevisiae and S. uvarum strains yields hybrids which have mitochondria of only a parental type: either of S. cerevisiae or S. uvarum. The peculiarity of examined hybrids is due to the homogeneity of their clone pop- ulations that are consisting of cells, all characterised by the same mitochondrial type. It seems to be probable to suppose an incompatibility of parental mitochondrial DNA (mtDNA).

Genetic polymorphism and metal sensitivity of Oidiodendron maius strains isolated from polluted soil

Abstract: Mycorrhizal isolates of Oidiodendron maius, recovered from Vaccinium myr- tillus that recolonized experimental plots polluted with different mixtures of toxic metals in the Niepolomice forest (Poland), were investigated for their genetic polymorphism and their ability to grow on metal ions. RAPD fingerprinting revealed the presence of distinct fungal genets. The same genet could be found in plots polluted with different metal mix- tures. Growth on culture media containing zinc, cadmium or aluminium ions showed that isolates collected on the polluted site were in general less sensitive to metals than strains of O. maius from non-polluted soils. However, their response on the different metal ions could not be correlated with the plot of origin or with the RAPD cluster. O. maius isolates with high and stable metal tolerance could be useful for bioremediation or to investigate the mechanisms of tolerance.

A global comparative method for the classification of world cheeses (with special reference to microbiological criteria). Revised edition

Abstract: A revised classification of cheeses and related products is proposed: three groups - Lacticinia, Formatica (cheeses) and Miscellanea - divided into 8 Classes and 45 Families. This note is to be considered a supplement of a previous paper.

Pathways of NADP+ and NAD+ degradation by Aspergillus niger extracts

Abstract: Extracts of an Aspergillus niger strain catalyzed degradation of NADP + and NAD + optimally at pH 4 and at pH 8 via a non-previously recognized pathway. Through this pathway NADP + was dephosphorylated to NAD + which then was cleaved to nicotinamide riboside plus ADP. The ADP formed was furtherly hydrolyzed to adenosine via the intermediate formation of AMP. At pH 4, the N-glycosidic linkage of adenosine was hydrolytically cleaved leading to the formation of adenine plus ribose. The extracts also catalyzed dephosphorylation of nicotinamide mononucleotide yielding nicotinamide riboside which could not be furtherly degraded. Phosphate release from each of NADP + , NAD + , ADP, and AMP was similarly affected as phosphate release from phenyl phosphate when tested under different experimental conditions. These conditions included different pH values, different temperatures, exposing the extracts to dialysis or to 75 °C for 5 min and addition of molybdate or magnesium to the reaction mixtures. NADP + and NAD + dephosphorylating enzymes were characterized as acid and alkaline phosphatases. Separation of the acid phosphatase from the alkaline phosphatase was achieved using Sephadex G-100 column chromatography.

Characterisation and typing of Saccharomyces strains by DNA fingerprinting

Abstract: Three different molecular methods, total DNA restriction profile analysis, restriction profile of mitochondrial DNA (mtDNA) and Southern hybridisation of mtDNA, were used to characterise Italian wine yeast strains previously identified using convention- al taxonomic techniques. Total DNA restriction profile analysis allowed the typing of all strains and showed that they constitute two well separated genomic taxa, one including the type strain of S. cerevisiae and the other the type strain of S. bayanus. The data obtained by analysing mtDNA restriction profiles and mtDNA Southern hybridisation were consistent with results of total DNA restriction profile analysis. This permitted the taxonomic assign- ment of Italian wine yeast strains and the determination of the interspecific genomic relat- edness.

Structure of foam and film forming cells of Saccharomyces cerevisiae

Abstract: Characteristics were described of the foam and film forming strains of Saccharomyces cerevisiae. These strains show a thin proteic layer at the cell surface that is absent in common non-foam and non-film forming strains. In young cells the proteic layer is not visible under a Scanning Electronic Microscope. The proteic layer becomes visible in old cells of foam forming strains because their surface becomes rough after collapse and contraction of the wall. In film forming cells, the proteic layer is rigid and preserves the original shape of the cells in the form of a blister after contraction of the wall. The strict correlation between these cell wall traits and capacity of forming foam and film were confirmed also by tetrad analysis of the hybrids obtained by crossing of segregants of these two types of strains.

Use of bioluminescence for rapid evaluation of fermentative activities during the first hours of large size cooked cheese ripening.

Abstract: In this paper, we describe the results of a study conducted in order to better evaluate the fermentative activity at the early phases of ripening of large size cooked cheeses. A rapid method based upon biochemical and enzymatic responses of ATP content determined by the use of bioluminescence was adopted in addition with culture methods based on viable counts of mesophilic and thermophilic lactic acid bacteria. The results obtained show that the bioluminescent response of total ATP content can be considered a valid, even non-specific, bioindicator for rapid evaluation of fermentative activities during the first hours of large size cooked cheese ripening.

Intraspecific characterization of indigenous Saccharomyces cerevisiae flor strains by mtDNA RFLP analysis

Abstract: In this study mitochondrial DNA restriction fragment length polymorphism (mtDNA RFLP) analysis was carried out on twenty flor strains, isolated from three different areas of Sardinia and representative of five dominant karyotypic groups previously determined by pulsed field gel electrophoresis (PFGE). The aim was to verify if the strains with the same karyotype also had identical mtDNA restriction profiles. In the Vernaccia production area the RFLP mtDNA analysis confirmed the homogeneity demonstrated by PFGE. In the areas of Planargia and Goceano, RFLP detected differences among strains of the same karyotypic group.

Enhancement and stabilization of diacetyl produced by cultures grown in whey.

Abstract: Effect of incubation at different temperatures, hydrogen peroxide-catalase treatment and cooling on the enhancement and stabilization of diacetyl production by the aroma bacteria in whey were investigated. Incubation of mixed strain aroma bacteria (Lactococcus lactis biovar. diacetylactis DRC1 plus Lactococcus lactis subsp. lactis 712 and Leuconostoc mesenteroides subsp. cremoris 543 plus Lactococcus lactis subsp. lactis 712) at 21 °C rather than at usual 30 °C and hydrogen peroxide-catalase treatment (whey with 0.03% H 2 O 2 and 0.004% catalase) prior to inoculation increased the diacetyl production by about 97% (2.46 ppm against 1.25 ppm) for the 1 st culture combination and about 43% (0.80 ppm against 0.56 ppm) for the 2 nd combination. Prompt cooling of fermented whey at 5 °C at the peak level of diacetyl production not only stabilized the flavour over a storage period of five days but also resulted in some increase (35% for the I st combination and 15% for the 2 nd combination) in diacetyl concentration. Because of its simplicity, effectiveness and nontoxicity the method may be used in the dairy industry for increasing the level and uniformity of flavour in fermented whey.

Sequence analysis of a PCR product from the iap gene of Listeria monocytogenes serovars most frequently isolated from food.

Abstract: After amplification and purification, PCR products from the iap gene of different Listeria monocytogenes serovars were subjected to sequencing to define the intraspecific differences within the gene encoding for the associated invasive protein Nucleotide sequence analysis of the tested serovars demonstrated a division into serovar-groups obtained by using restriction enzyme analysis and single strand conformation polymorphism Three groups were identified: the first included serovars 1/2a and 3a, the second serovars 1/2b, 3b and 4b, and the third serovar 1/2c