小单孢菌科放线菌的研究进展

小单孢菌科（Micromonosporaceae）菌株是一类具有气生菌丝和基内菌丝分化的经典放线菌,于二十世纪中期被发现,目前包含29属246种的成员。这类菌株不仅广泛分布于普通的陆地生态系统中,在淡水生态系统、海洋生态系统以及一些被认为对生命极具挑战的极端环境中也常能探测到这些微生物的踪迹。小单孢菌产生的抗生素和其他生物活性物质被广泛应用于医疗和农业的多个领域,一直以来受到研究人员的广泛关注。本文就小单孢菌科放线菌的分类学特征、生态分布、基因组特征及其在医药和农业领域的应用情况进行了综述,以期为推进小单孢菌科放线菌资源的高质量发掘奠定基础。     

Various methodological approaches in controlled screening of antibiotic producers among the group of Coryneform bacteria]

A methodical system for directed screening of cultures producing broad-spectrum antibiotics among soil saprophytic coryneform bacteria was developed. To isolate such cultures, it was recommended to use the glucose-yeast medium supplemented with malt extract (No. 18/3) and soybean-glucose medium with sodium sulfate and cobalt chloride (No. 20/3). The preliminary alkaline treatment of the soil substrates and the use of acidic soil samples were found to favour isolation of the Mycobacterium type cultures. It was recommended to use gram-negative tests microbes with relatively low antibiotic resistance for screening cultures producing broad spectrum antibiotics. Various agarized and liquid fermentation media were compared in regard to detection of antibiotic activity in the soil coryneform bacteria. The corn medium supplemented with protein-vitamin concentrate, glucose, lactose and starch (No. 116) proved to be the most efficient.     

Various principles of detecting the producers of beta-lactamase inhibitors among soil Actinomycetes

Principles of detecting organisms producing beta-lactamase inhibitors among soil actinomycetes were developed. For detecting such cultures it was recommended to use the Gauze agarized medium No. 1 supplemented with beta-lactam antibiotics. Benzylpenicillin proved to be the most efficient. Various liquid fermentation media for detecting the inhibitory activity of soil actinomycetes were compared. Two media were the most favourable i.e. the glucose-yeast medium No. 18/3 and the soybean-glucose medium with Na2SO4 and CoCl2 No. 20/3. The use of test cultures with relatively low resistance to benzylpenicillin was shown expedient in screening cultures producing beta-lactamase inhibitors. Test cultures with high resistance should be used in more detailed characterization of the selected cultures.     

Determination of the filtration characteristics of the fermentation broths of antibiotic producers]

Main filtration characteristics of the fermentation broths are necessary for estimation of the filtration equipment, rational choice of the filtering apparatus, determination of the optimal conditions for their exploitation. In this connection studies were carried out with a purpose of determining the specific resistance and the content of the solid phase in the fermentation broths of the main antibiotics. It was shown that the above characteristics were closely connected with the biosynthetic conditions and medium composition. It was noted that the specific resistance of the precipitates of the fermentation broths of various antibiotic-producing organisms significantly differed, sometimes by several orders. Preliminary treatment of the fermentation broths before filtration provided a marked decrease in the resistance of the precipitate.     

Immunoenzyme method for detecting microbial producers of palytoxin

A competitive ELISA using the intact toxin as a coating antigen for detecting palytoxin was developed. This immunoassay allows palytoxin (PTX) to be determined in the range of 6-250 ng/ml. In sensitivity, this determination is comparable with RIA but is three times inferior to ELISA using monoclonal antibodies. Inhibition experiments using some toxins of marine invertebrates proved the serological specificity of the palytoxin binding to antibodies. Both the indirect and competitive ELISA were used to find PTX-producing bacteria among 420 isolates of sea bacteria. It was found that gram-negative bacteria Aeromonas sp. and Vibrio sp. associated with toxic samples of the soft coral Palythoa sp. produced compounds antigenically related to PTX.     

Effect of partial pressure of solute oxygen on the intensity of respiration of cultures of antibiotic producers

It was shown possible to use feeding of hydrogen peroxide as a method for investigating the impact of dissolved oxygen concentrations on growth and development of microorganisms. The influence of pO2 on the respiration intensity was studied in penicillin- and erythromycin-producing cultures and it was found that dependence of the respiration intensity on pO2 had the form of a curve with saturation, at pO2 equal to zero the value of the culture respiration intensity being different from zero. A mathematical model accounting for the presence in the fermentation broth of microbial agglomerates with the average size depending on the agitation conditions is proposed for describing the relationships.     

Rapid screening procedures for identification of succinic acid producers

Succinic acid, an intermediate of tricarboxylic acid cycle, is produced and accumulated by anaerobic microorganisms. The long-standing interest in the production of this organic acid is because it is a key compound in producing more than 30 commercially important products. The detection of succinic acid is generally carried out by gas chromatography (GC), enzymatic assays, ion-exclusion chromatography (IEC) or by high performance liquid chromatography (HPLC). However, these methods are time consuming, require sophisticated instrumentation and are expensive. In the present investigation we are reporting two rapid, cost effective screening methods for the detection of this important organic acid. These methods can be utilized to screen a large number of microbes producing succinic acid in a very short span of time.     

Methodological approaches to developing a method of regulated antibiotic biosynthesis]

Methodologic approaches to the development of methods for controlled biosynthesis of antibiotics are discussed with reference to oxytetracycline biosynthesis. The method of acute experiments in conjunction with mathematical methods of experiment planning was used for determination of the substrate concentrations optimal for the culture growth and biosynthesis of oxytetracycline. It was found that such mathematic procedure provided simultaneous determination of optimal concentrations of all the substrates.     

Direct screening for producers of antibiotics among the Micromonospora

A test system was developed for screening organisms producing antibiotics of definite chemical groups or mechanisms of action. The system includes efficient selection of cultures belonging to a definite microbiological taxon (genus Micromonospora), investigation of their biological and taxonomic features, the use of specific selective media with high concentrations of definite antibiotics for isolating antibiotic-producing cultures from natural substrates, the use of specific methods for antibiotic chemical isolation at the initial stages of the screening and chromatographic study of the screened compounds. The system provided efficient screening of valuable antibiotics in a short period.     

Search for methanotrophic producers of exopolysaccharides]

Bacteria that produce exopolysaccharides (EPS) and use methane as the only source of carbon were selected by studying a collection of methanotroph strains: Methylococcus capsulatus E 494, 874, and 3009; M. thermophilus 111p, 112p, and 119p; Methylobacter ucrainicus 159 and 161; M. luteus 57v and 12b; Methylobacter sp. 100; Methylomonas rubra 15 sh and SK-32; Methylosinus trichosporium OV3b, OV5b and 4e; M. sporium 5, 12, A20d, and 90v; and Methylocystis parvus OVVP. Mesophilic methanotroph strains with the ribulose monophosphate way of C1-compound assimilation synthesized EPS more actively than bacteria operating the serine cycle. The dynamics of EPS synthesis by methanotrophs during chemostat cultivation was studied.     

Controlled search for the producers of ionophore antibiotics among Streptomycetes

A procedure was developed for directed screening of cultures producing ionophore antibiotics among streptomycetes. The procedure is based on measuring the membrane potential generated in the presence of the Men+/nH+ = -expchanger-protonophore couple. It provided isolation of cultures producing ionophore antibiotics at the fermentation broth stage. It was possible to use the procedure in screening both electrogenic and nonelectrogenic ionophores and to rapidly differentiate them. 5 cultures producing ionophore antibiotics were detected with this procedure; 3 of them carry out nonelectrogenic transport of the cations. The cation transport in the other two cultures was electrogenic. Cation selectivity of the antibiotics produced by the cultures was determined with the procedure. An antibiotic identical to indanomycin was isolated from the culture fluid of Streptomyces chromogenes.     

Use of polymerase chain reaction for searching for producers of ergot alkaloids from among microscopic fungi]

The potential of the polymerase chain reaction for the detection of ergot alkaloid producers among microscopic fungi of the genera Penicillium and Claviceps was evaluated. Twenty-three strains of various species of fungi with a previously studied capacity for alkaloid production were used. The internal fragment of the gene encoding 4-dimethylallyltryptophan synthase, the enzyme catalyzing the first step in the biosynthesis of ergot alkaloids, was amplified using degenerated primers. This approach revealed an about 1.2-kb specific DNA fragment in micromycetes synthesizing ergot alkaloids with complete tetracyclic ergoline system. Microorganisms that produce alkaloids with modified C or D ergoline rings, as well as alpha-cyclopiazonic acid, did not yield the PCR fragment of the expected size. This fragment was also not found in fungi incapable of ergot alkaloid production.     

Frequency and antibiotic resistance of bacteria isolated from urine cultures]

The AA report the data pertinent to the urine culture performed during a year in the Sanitary and Prophylactic Laboratory of the district of L'Aquila. In urine samples with number of bacteria > 10(5)/ml have been found E. coli (49%), Proteus mirabilis (32%), Pseudomonas aeruginosa (12%), Staphylococcus aureus (5%), Proteus rettgeri (1%), Enterococco (1%). The data are also reported concerning germ resistance to several antibiotics.