Death of Bacteria in Growing Culture

Genetic transformations of pneumococcus mediated by streptomycin-induced lysates were studied to gain some insight into the nature of freshly released transforming principle, and the influence of the physiologic state of the donor population on the transformation process. It was found that streptomycin could make the DNA of sensitive cells available for transformation of other cells. Living cultures of pneumococcus growing exponentially in ordinary media were also found to discharge significant quantities of genetically active DNA. Such cultures, not treated with any drug, showed no evidence of concomitant cell disintegration or death. Both single markers and small linkage groups could be transferred in transformations mediated by drug-induced lysates and by filtrates of living cultures. The quantity of DNA liberated is small (less than 0.1 µg per ml), but these transformations are at least as efficient as transformations mediated by purified DNA, when compared on the basis of total DNA available. Up to 1 per cent of the cells in an average recipient culture can be transformed by a small quantity of culture fluid. Both in drug-treated and in untreated cultures the amount of transforming activity increased and then decreased during growth of the culture. Although the source of transforming DNA in growing cultures could not be established, the decline in the transforming activity of aging drug-treated or untreated cultures was attributed to the presence of deoxyribonuclease. The release of this nuclease by pneumococcal cultures midway in exponential growth is sufficient to result in a mild degradation of the low concentration of freshly released transforming agent present. Maximal release of active transforming agent by a living culture coincided in time with the development of maximal receptivity to exogenous DNA by that culture. As a result, recombinants could be recovered from appropriately genetically marked strains growing in each other's presence. In view of these results, it seems possible that DNA-mediated transformations might provide, or might have provided, a mechanism of genetic recombination in nature for some bacterial species in which sexual mechanisms may not be available.

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“…Studies on Escherichia coli(27) also seem to indicate that cell death is rare during active growth of the population.…”

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confidence: 99%

Release of Genetic Transforming Agent From Pneumococcal Cultures During Growth and Disintegration

Ottolenghi

Hotchkiss

1962

The Journal of Experimental Medicine

119

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“…On the other hand, the stability of 6-galactosidase is much greater than the 5 per cent per hour ( corresponding half life, 14 hours ) loss of various isotopes in growing culture found by Koch (1959), and attributed by him to death of cells caused by centrifugation of cells in the cold; or the 5 per cent per hour found by Mandelstam (1958) in starved suspensions, and attributed by him to intracellular turnover. The first phenomenon of death of cells caused by chilling was first described by Hegarty and Weeks ( 1940) and is possibly related to the energy and carbon starvation initiated lysis of bacteria, when the culture is subsequently resupplied with an energy and carbon source, as previously described.…”

Section: How Stable Ismentioning

confidence: 80%

The INACTIVATION OF THE TRANSPORT MECHANISM FOR Β‐GALACTOSIDES OF ESCHERICHIA COLI UNDER VARIOUS PHYSIOLOGICAL CONDITIONS

Koch

1963

Annals of the New York Academy of Sciences

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“…This could also explain the larger standard variation of colonies in viable count when compared to the number of autoradiographic bacteria (Table 1). As the time between death and lysis of bacteria is rather short (Koch, 1959) it is unlikely that dead bacteria cause a large part of the difference in number between autoradiographicallydemonstrated bacteria and counted colonies. The decrease in the number of colonies on viable count after storage of water samples corresponds to the findings of earlier authors (PHLS Water Committee 1953).…”

Section: Discussionmentioning

confidence: 99%

Autoradiographic detection of radioactive bacteria introduced into sea water and sewage

Berlin

Rylander

1963

J. Hyg.

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The agency of water in the dissemination of bacteria and viruses has long been recognized, but though measures have been taken to control this hazard, water still plays a large role in spreading pathogens such as enterovirus and salmonella. A simple and reliable method for studying dissemination of this kind would therefore be most useful.The presence in water of thermostable coli bacteria is generally considered an index offaecal contamination. Unfortunately, their detection in a water sample is a laborious procedure which requires growing cultures, often on different media, for confirmation. Furthermore, the significance of one particular source of contamination when several are present cannot be determined with current bacteriological technique. The problem has been previously attacked by using mutants of the contaminating micro-organisms, or indicator organisms such as Serratia (Robson, 1956). The tracer bacteria are added to the water at the source of contamination and water samples are taken for bacteriological examination.Radioactive substances and dyes have also been used to study the spread of contamination (Montens, 1954;Ely, 1957). Because of rapid dilution, high levels of radioactivity are necessary to follow dispersion in large volumes of water. In addition, the action of biological factors on the survival of contaminating bacteria cannot be ascertained with these materials alone.Bacteria which have been radioactively labelled can be used as tracer organisms. If they can be detected by a method which avoids the necessity of culturing water samples and if the method is sufficiently sensitive, the use of radioactive bacteria offers several advantages. In the present paper such a method is described, for use in studying the spread of bacteria in water. Water samples were filtered through a Millipore filter and an autoradiogram of the filter was prepared in which the bacteria appeared as black spots. The accuracy and sensitivity of the method were estimated and a test made under field conditions. METHODS Strain B Escherichia coli were used. The bacteria were grown overnight at 370 C. in agitated 500 ml. flasks on Andersson's synthetic medium.* The medium was modified by replacing MgSO4 with MgC12 to eliminate carrier sulphur. One micro-* MgSO4, 04 g.; Na2HPO4, 6 g.; KH2PO4, 3 g.; NaCl, 5 g.; NH4C1, 1 g.; glucose, 4 g.;H20, ad 1000 ml.; pH = 7.

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Death of Bacteria in Growing Culture

Cited by 33 publications

References 24 publications

Release of Genetic Transforming Agent From Pneumococcal Cultures During Growth and Disintegration

Release of Genetic Transforming Agent From Pneumococcal Cultures During Growth and Disintegration

The INACTIVATION OF THE TRANSPORT MECHANISM FOR Β‐GALACTOSIDES OF ESCHERICHIA COLI UNDER VARIOUS PHYSIOLOGICAL CONDITIONS

Autoradiographic detection of radioactive bacteria introduced into sea water and sewage

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