Observations on the multiplication of phages affecting Streptomyces griseus

Bacteriophage Challenges in Industrial Processes: A Historical Unveiling and Future Outlook

Humans have used fermentation processes since the Neolithic period, mainly to produce beverages. The turning point occurred in the 1850s, when Louis Pasteur discovered that fermentation resulted from the metabolism of living microorganisms. This discovery led to the fast development of fermented food production. The importance of industrial processes based on fermentation significantly increased. Many branches of industry rely on the metabolisms of bacteria, for example, the dairy industry (cheese, milk, yogurts), pharmaceutical processes (insulin, vaccines, antibiotics), or the production of chemicals (acetone, butanol, acetic acid). These are the mass production processes involving a large financial outlay. That is why it is essential to minimize threats to production. One major threat affecting bacteria-based processes is bacteriophage infections, causing substantial economic losses. The first reported phage infections appeared in the 1930s, and companies still struggle to fight against phages. This review shows the cases of phage infections in industry and the most common methods used to prevent phage infections.

Bacteriophage-resistant industrial fermentation strains: from the cradle to CRISPR/Cas9

Bacteriophage contamination and cell lysis have been recurring issues with some actinomycetes used in the pharmaceutical fermentation industry since the commercialization of streptomycin in the 1940s. In the early years, spontaneous phage-resistant mutants or lysogens were isolated to address the problem. In some cases, multiple phages were isolated from different contaminated fermentors, so strains resistant to multiple phages were isolated to stabilize the fermentation processes. With the advent of recombinant DNA technology, the early scaleup of the Escherichia coli fermentation process for the production of human insulin A and B chains encountered contamination with multiple coliphages. A genetic engineering solution was to clone and express a potent restriction/modification system in the production strains. Very recently, an E. coli fermentation of 1,3-propanediol was contaminated by a coliphage related to T1. CRISPR/Cas9 technology was applied to block future contamination by targeting seven different phage genes for double-strand cleavage. These approaches employing spontaneous mutation, genetic engineering, and synthetic biology can be applied to many current and future microorganisms used in the biotechnology industry.

Isolation of Streptomyces rimosus Mutants with Reduced Actinophage Susceptibility

The infection of Streptomyces rimosus by the virulent actinophage RP1 was partially characterized. RP1 infection of the host cells results in a dramatic decrease in viable cell count, followed by reduced antibiotic production. Phage-resistant mutants were isolated after mutagenic treatment and RP1 selective pressure. Characterization of the isolated mutants has revealed that RP1 infection had no influence on their growth and antibiotic production. However, multiplication of the phage particles in the lawns of resistant mutants was detected. Since these strains differ from the wild type in RP1 relative efficiency of plating, plaque morphology, and the time necessary for plaque appearance, they are considered to be semiresistant mutants. The propagation of RP1 on semiresistant strains is characterized by lower adsorption of phage particles and longer latent and rise periods. As a consequence, the multiplication of the phage is slower than that of their host, which consequently reduces the ratio of phage to its host, thus diluting out the phage.

Characterization of the virulent actinophage S2

The virulent actinophage S2 isolated from soil infects Streptomyces hygroscopicus 6599, S. lividans 66, and S. levoris 1331. Morphology of S2 was studied by electron microscopy. Influence of growth medium and temperature on multiplication of S2 has been studied qualitatively. S2 is more sensitive to UV irradiation on strain 66 than on 1331. In contrast to UV, hydroxylamine mutagenesis delivered 9 stable ts mutants which belong to 3 complementation groups. Most of the ts mutations isolated on 1331 were found to be host dependent, 8 of 9 mutants were found to be able to grow at 40 degrees C on strain 66 but none of them on 1331. Moreover 2 of the mutants were found to be much more heat sensitive in 6599 than in 1331, as indicated by the changes in half-life temperatures. The latent period of S2+ depends on temperature and germination state of the spores. Under optimal conditions we found 140 min. Ts2 and ts7 have been classified as a late and ts17 as an early mutant.

Electron microscope study of the multiplication of the actinophage affecting Streptomyces griseus

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