# Bacterial Therapy of Cancer: A Way to the Dustbin of History or to the Medicine of the Future?
## 2 Bacterial Dualism: What Can Kill Can Also Heal  
### In Pursuit of the \"Cancer Germ\"  
Numerous data indicating a certain role of bacteria in the origin and pathogenesis of malignant neoplasms have been repeatedly obtained. Beginning in the mid-19 th century, microbiologists examining tumor tissues microscopically discovered in them a variety of microorganisms [14]. Additionally, although the 150-year-old research can be viewed with some skepticism due to the lack of sterility at that time, more recent works probably deserve more attention. By the beginning of the 20 th century, the principles of asepsis were generally defined and increasingly introduced into medical and surgery practice--this reduced the chance that the microorganisms observed by researchers in surgery tumors were introduced from the outside. Thus, in the works of [PERSON] (1895), [PERSON] (1899), [PERSON] (1921), and [PERSON] (1934), some microorganisms observed in tumors of various etiologies were described. In some cases, these microorganisms were successfully cultured on special media, and when trying to introduce a culture of these microorganisms to animals, tumors occasionally developed [14; 15; 16]. In 1885, a French scientist, [PERSON], isolated from the different tumors a bacterium that he named _Microoccus neoformans_. This microorganism had an extremely small size (about 0.13 microns) and was located in the tumor tissues both intracellularly and in the intercellular space. When inoculated into animals, it \"gave rise to neoplastic formations\" [14; 15; 17]. However, subsequent studies have not been able to confirm the etiological significance of \"_Microoccus neoformans_\" in the pathogenesis of malignant tumors [17]. [PERSON] and [PERSON] noted that this microorganism was similar and may be related to the staphylococcal species [17]. Many researchers have noted the pleomorphism of microorganisms isolated from tumors. Thus, in 1930, [PERSON] obtained from an adenocarcinoma of the human breast an intracellular organism that was shown in subculture to be highly pleomorphic: its lifecycle included coccoids, rods, mycelial stages, and filter-passing forms. The introduction of a culture of this microorganism to dogs, guinea pigs, rats and mice, as well as monkeys, in some cases led to the appearance of tumors in them [15]. Three-quarters of a century later, a work was published suggesting that \"[PERSON]'s organism\" might be the highly pleomorphic bacterium _Bacillus licheniformis_; however, this idea was not evolved [18]. Similar observations of pleomorphic microorganisms can be found in the works of [PERSON] (1925) [19], [PERSON] (1927) [20], and [PERSON] (1947) [14; 15]. Thus, [PERSON] cultured Gram-positive microococci from breast tumors. These cocci were facultative anaerobes; they did not grow on solid media, but could be successfully cultured on astic fluid. Their size varied from 0.1 to 0.3 \(\upmu\)m depending on the growth stage, and larger forms similar to staphylococci appeared in older cultures. Microscopic studies have shown that these microorganisms can be discovered both in the intercellular fluid and in the cytoplasm of tumor cells. Inoculation with this bacterium into mice and dogs caused the development of some precancerous lesions and, in some cases, mammary carcinomas [14; 19]. [PERSON], together with [PERSON], and other scientists, found that there were microorganisms in malignant tumors of different histogenesis that could be isolated and cultured. Histological and microscopic studies have shown that this \"mycobacterium like\" specific microorganism (called _\"Mycobacterium tumefaciens\"_) is extremely polymorphic and can represent mobile rods, cocci, or the smallest filterable forms [21]. Mobile rods were easily cultured on conventional media, while the growth of small filterable forms was achieved only on special media. Different forms of the microorganism were differently Gram-stained [14].