Anaerobic bacteria as producers of antibiotics

Anaerobic bacteria are the oldest terrestrial creatures. They occur ubiquitously in soil and in the intestine of higher organisms and play a major role in human health, ecology, and industry. However, until lately no antibiotic or any other secondary metabolite has been known from anaerobes. Mining the genome sequences of Clostridium spp. has revealed a high prevalence of putative biosynthesis genes (PKS and NRPS), and only recently the first antibiotic from the anaerobic world, closthioamide, has been isolated from the cellulose degrading bacterium Clostridium cellulolyticum. The successful genetic induction of antibiotic biosynthesis in an anaerobe encourages further investigations of obligate anaerobes to tap their hidden biosynthetic potential.     

Entomopathogenic bacteria Bacillus thuringiensis as producers of restriction endonucleases

A total of 115 collection strains of Bacillus thuringiensis, belonging to various subspecies, have been studied for the presence of DNA restriction-modification systems. Restriction endonucleases of 13 strains have been isolated and characterized. No considerable correlations between the taxonomic positions of the bacteria and the specificities of the endonucleases isolated have been detected. It is concluded that the enzymes with identical specificities are present in both the crystalliferous and acrystalliferous strains of the same subspecies.     

Aerobic endospore-forming bacteria isolated from Antarctic soils as producers of bioactive compounds of industrial interest

Spore-forming bacteria are known to produce various enzymes and bioproducts valuable to different industries and to bear the harsh conditions found in the Antarctic environment. However, aerobic or facultative spore-forming bacterial communities found in maritime Antarctic soils yet remain poorly studied. In this study, 80 spore-forming and cold-adapted bacterial strains were isolated from nine different soil samples of King George Island, in maritime Antarctica, and further clustered into amplified ribosomal DNA restriction analysis groups within each soil. Representative strains were then identified as belonging to Bacillus, Rummeliibacillus, Paenibacillus and Sporosarcina by 16S rRNA gene sequencing. The ability to produce extracellular enzymes, antimicrobial substances and biosurfactants was determined in all isolates. The enzymatic activities most frequently found among the isolates were as follows: esterase (45 %), caseinase (30 %), amylase (16.2 %) and gelatinase (15 %). Biosurfactant production was detected in 25 % of the isolates. The growth inhibition of methicillin-resistant Staphylococcus aureus was observed in 13.7 % of the strains tested, but only two strains inhibited the growth of Candida albicans. The isolated spore-forming bacterial species were also compared with the characteristics of the different Antarctic soils sampled based on their physicochemical properties, showing that pH, C and P were the main factors correlated with the distribution of this group of bacteria in the Antarctic soils studied. These Antarctic endospore-forming bacterial strains may have a potential for industrial processes occurring at low temperatures.     

Binding of Fusarium mycotoxins by fermentative bacteria in vitro

AIMS: Fusarium toxins can occur in conserved forages impairing farm animal performances and health. On-farm biological decontamination methods could be an alternative to traditional physico-chemical methods. In this work, the ability to remove Fusarium toxins by fermentative bacteria was evaluated in vitro. METHODS AND RESULTS: Twenty-nine strains of lactic (LAB) and propionic acid bacteria (PAB) were tested for their ability to remove deoxynivalenol (DON) and fumonisins B1 and B2 (FB1, FB2) from an acid, pH 4, medium. Mycotoxin removal was widespread for LAB, but differences among strains were large. Removal was up to 55% for DON, 82% for FB1 and 100% for FB2. Selected strains were also capable of removing up to 88% zearalenone. The PAB strains were less efficient than the LAB. Binding, not biodegradation appeared to be the mode of action, as no toxin derivatives were observed and removal was not impaired in nonviable bacteria. Binding was not affected by pH, except for fumonisins that decreased to nearly 0% at neutral pH. CONCLUSIONS: Selected fermentative bacteria are able to bind main Fusarium mycotoxins. SIGNIFICANCE AND IMPACT OF THE STUDY: The binding ability of selected strains could be used to decrease the bioavailability of toxins in contaminated silages.     

Actinomadura species as antibiotic producers

Screening of antibiotic-producing cultures among Actinomadura showed that definite species mainly produced antibiotics of the same groups. Thus, carminomycins were produced by all the 4 studied strains of A. carminata, maduramycins were produced by 3 strains of A. rubra, prodigiozines were produced by 3 strains of A. madurae and luzopeptines were produced by 6 strains of A. recticatena. Supposedly, new antibiotics with original spectral characteristics were isolated from 2 strains of A. fulvescens. There was a clear-cut relation of the number of the active strains and their antibiotic productivity in definite media to their species. The liquid nutrient media, such as yeast-sucrose, soya-glucose and soya-glucose with cobalt chloride proved to be the most efficient in the primary screening of antibiotic-producing cultures.     

Cold-adapted yeasts as producers of cold-active polygalacturonases

Eight cold-adapted, polygalacturonase-producing yeasts belonging to four species were isolated from frozen environmental samples in Iceland. They were identified as Cystofilobasidium lari-marini, Cystofilobasidium capitatum, Cryptococcus macerans and Cryptococcus aquaticus species by sequence analysis of rDNA regions. Growth behavior of the isolates was investigated. All strains could grow at 2 degrees C. Addition of glucose to pectin-containing culture medium had a repressive effect on enzyme production except for C. aquaticus, which showed increased polygalacturonase activity. Optimal temperature for enzyme production for the Cystofilobasidium strains was 14 degrees C, while that for the Cryptococcus strains was lower. Among the isolates, C. lari-marini S3B produced highest levels of enzyme activity at pH 3.2. Preliminary characterization of the polygalacturonases in the culture supernatant showed the enzyme from Cystofilobasidium strains to be optimally active at 40 degrees C and pH 5, and that from the Cryptococcus strains at 50 degrees C and pH 4. The polygalacturonase from C. macerans started to lose activity after 1 h of incubation at 40 degrees C, while that from the other strains had already lost activity at 30 degrees C. All the strains except C. aquaticus produced isoenzymes of polyglacturonase. In addition to polygalacturonase, the Cystofilobasidium strains produced pectin lyase, C. aquaticus pectin esterase, and C. macerans pectin lyase, pectate lyase and pectin esterase.     

Microorganisms as potential producers of essential fatty acids

The data on the importance of essential fatty acids in a balanced diet have been considered. The ways of essential fatty acid synthesis in microorganisms and their metabolism in animal tissues are being discussed. The criteria for microorganisms selection--producers of food lipids have been proposed.     

Phosphate-mobilizing bacteria <Emphasis Type="Italic">Bacillus subtilis</Emphasis> as phenolic producers

Bacteria Bacillus subtilis IMVV-7023 accumulate biologically active phenolic substances in the culture liquid. They include significant amounts of phenylacetic (29.03%) and 4-hydroxyphenylacetic (10.49%) acids. These acids can induce root formation in plants. They also suppress fungal plant pathogens.     

Screening of thermotolerant yeasts as producers of superoxide dismutase

Abstract A screening procedure for highly thermostable yeast superoxide dismutase was developed. Growth yields at various temperatures were estimated for ten mesophilic and thermotolerant strains, belonging to the genera Saccharomyces, Kluyveromyces and Pichia . Higher yields at 45°C were obtained for K. lactis 90-3 and 90-4. A correlation between the ability to grow at higher temperature and the thermostability of the superoxide dismutase enzyme synthesized was observed. A comparison of the operational stability of the superoxide dismutase of all tested strains suggests that the enzyme of K. lactis strains was more thermostable than that of the other tested microorganisms.     

Interspecies mouse-mink hybridomas as producers of mink immunoglobulin]

The work is aimed at establishing the interspecies mouse-mink hybridomas from the fusion of American mink B-lymphocytes with the murine cell line NSO. The hybridoma (lime 10-B5) continued to secrete mink immunoglobulin L-chains in the culture for 6 months with constant reclonings. The hybridoma clone was characterized by a decrease in the secretory activity of cells. The karyological study et this clone has not reliably revealed the mink chromosomes in the genome of hybrid cells.     

Marine yeasts as biocontrol agents and producers of bio-products

As some species of marine yeasts can colonize intestine of marine animals, they can be used as probiotics. It has been reported that β-glucans from marine yeast cells can be utilized as immuno-stimulants in marine animals. Some siderophores or killer toxins produced by marine yeasts have ability to inhibit growth of pathogenic bacteria or kill pathogenic yeasts in marine animals. The virulent factors from marine pathogens can be genetically displayed on marine yeast cells, and the yeast cells displaying the virulent factors can stimulate marine animals to produce specific antibody against the pathogens. Some marine yeast cells are rich in proteins and essential amino acids and can be used in nutrition for marine animals. The marine yeast cells rich in lipid can be used for biodiesel production. Recently, it has been reported that some strains of Yarrowia lipolytica isolated from marine environments can produce nanoparticles. Because many marine yeasts can remove organic pollutants and heavy metals, they can be applied to remediation of marine environments. It has been shown that the enzymes produced by some marine yeasts have many unique properties and many potential applications.     

Pediococcus spp.: An important genus of lactic acid bacteria and pediocin producers

Probiotics have gained increasing attention due to several health benefits related to the human digestive and immune systems. Pediococcus spp. are lactic acid bacteria (LAB) that are widely described as probiotics and characterized as coccus-shaped bacteria (arranged in tetrads), Gram-positive, non-motile, non-spore forming, catalase-negative, and facultative anaerobes. There are many Pediococcus strains that produce pediocin, an effective antilisterial bacteriocin. Pediocins are small, cationic molecules consisting of a conserved hydrophilic N-terminal portion containing the YGNGV motif and an amphiphilic or hydrophobic C-terminal variable portion. A number of studies have been developed with Pediococcus isolated from multiple biological niches to conduct fermentation processes for pediocin or Pediococcus cell production. This review gathers the most significant information about the cultivation, mode of action, and variability of bacteriocins produced by Pediococcus spp., emphasizing their applications in the areas of food and clinical practice. This updated panorama assists in delimiting the challenges that still need to be overcome for pediocin use to be approved for human consumption and the food industry.     

Rare genera of actinomycetes as potential producers of new antibiotics

A literature survey covering more than twenty-three thousand bioactive microbial products including eight thousand antiinfectives demonstrated the increasing relevance of the so called 'rare' actinomycetes as a source of new antibiotics. Past and present efforts in the isolation of rare actinomycetes have enriched the Biosearch Italia Strain Collection with more than twenty thousand strains, showing that, when selective isolation methods are developed and extensively applied, some genera, such as Actinomadura, Actinoplanes, Micromonospora, Microtetraspora, are not rare at all and can be recovered from many soil samples. The current focus is on the isolation of members of Streptosporangiaceae family, given their promising chemical diversity.     

Bacterial bioluminescence as a bioassay for mycotoxins.

The use of bacterial bioluminescence as a toxicological assay for mycotoxins was tested with rubratoxin B, zearalenone, penicillic acid, citrinin, ochratoxin A, PR-toxin, aflatoxin B1, and patulin. The concentrations of mycotoxins causing 50% light reduction (EC50) in Photobacterium phosphoreum were determined immediately and at 5 h after reconstitution of the bacteria from a freeze-dried state. Generally, less toxins were required to obtain an EC50 at 5 h. The effects of the above mycotoxins on bioluminescence were determined after 5, 10, 15, and 20 min of incubation with the bacterial suspensions. The concentration of rubratoxin B necessary to elicit an EC50 increased with time, whereas the concentration of citrinin, penicillic acid, patulin, and PR-toxin necessary decreased with time. There was very little change in the concentration of zearalenone, aflatoxin B1, and ochratoxin A required to elicit an EC50 with time. The bacterial bioluminescence assay was most sensitive to patulin and least sensitive to rubratoxin B.