Showing papers in "Journal of Bacteriology in 1950"

Mutants of escherichia coli requiring methionine or vitamin b12

Abstract: The penicillin method (Davis, 1948; Lederberg and Zinder, 1948) has permitted convenient isolation of auxotrophicl mutants of Escherichia coli with specific growth requirements for most of the known water-soluble vitamins, as well as amino acids, purines, and pyrimidines. Accordingly, when crystalline vitamin B12 became available, a search was made for mutants requiring this nutrilite. Several strains of the desired type were promptly recovered. In all cases methionine, but not homocysteine, could be substituted for the vitamin. This paper describes certain biochemical properties of these mutants, as well as of others responding to methionine but not to B,2.

The biological degradation of soluble cellulose derivatives and its relationship to the mechanism of cellulose hydrolysis.

Abstract: The use of soluble cellulose derivatives in the form of gels for pharmaceutical and other purposes depends in part upon the resistance of the preparation to liquefaction. Reports have reached us that products containing soluble carboxymethyl cellulose (CMC) liquefied on standing. From one of the deteriorated samples Woodward (1948) isolated Aspergillus niger and AspergiUus flavus; from another preparation Freeman et al. (1948) obtained gram-negative bacteria, which on reinoculation, again liquefied the CMC. Contaminated hydroxyethyl cellulose preparations behave in a similar fashion. From one sample Harry (1948) isolated two bacterial organisms. In a study of the availability of cellulose derivatives to Myrothecium verrucaria, Siu et al. (1949) found that CMC-Na salt and methocel (soluble methyl cellulose) were metabolized. From our viewpoint several points appeared to require further elucidation. How widespread is the ability of microorganisms to utilize soluble cellulose derivatives as carbon sources? How do the number, nature, and location of the substituents affect the availability of the modified cellulose? And, finally, is there any relationship between the enzymatic hydrolysis of cellulose derivatives and the hydrolysis of cellulose itself? These are the questions to which the following data are partial answers.

The influence of certain salts, amino acids, sugars, and proteins on the stability of rickettsiae.

Abstract: It is well recognized that most of the species of pathogenic rickettsiae rapidly lose viability in the usual bacteriological media at room temperature, or even at O C. For several reasons it was desirable to find a simple medium that would be as favorable as possible for the survival of rickettsiae. Such a medium was required not only for use as a diluent in animal assays but also for the preparation of purified rickettsiae of undiminished viability. Furthermore, it seemed an essential first step in any attempt to grow these organisms in vitro. It was known from the work of Anderson (1944) that two media were favorable for rickettsiae, namely, skim milk and a 20 per cent suspension in nutrient broth of yolk sac membrane from normal chick embryos. Both of these media are obviously unsuitable for use in purification. Therefore a study of the stability of rickettsiae in solutions of varying composition was undertaken and has led to the development of media that, under certain conditions, appear to be at least as effective as milk in preserving the viability of rickettsiae. However, even in the most favorable media, the rickettsiae cannot be kept longer than 24 hours at 0 C or above without significant decreases in titer (with the possible exception of Q fever rickettsiae). For any metabolic studies with purified rickettsiae it was necessary to have preparations that would be stable for at least a week, and preferably for much longer. This is readily accomplished with suspensions of crude infected yolk sac material, which can be rapidly shellfrozen and stored at -72 C without loss in viability of the rickettsiae. When purified rickettsiae are similarly frozen and stored, however, the losses are so great that the suspensions are entirely unsuitable for metabolic studies. Therefore media have also been developed that make possible the freezing and storage of purified rickettsiae with very slight loss in viability.

An iron-oxidizing bacterium from the acid drainage of some bituminous coal mines

Abstract: As late as 1945 Starkey called attention to the incompleteness of the information concerning the true autotrophic nature of iron bacteria, and to the confusion existing as to whether any bacteria in iron-bearing waters are concerned directly or indirectly with the precipitation of iron from the waters. The recent critical summary of researches on the iron bacteria by Pringsheim (1949) indicates a continuing interest in this member group of the Chlamydobacteriales, and, as Pringsheim states, "The general interest in iron bacteria is apparently greater than that bestowed upon other biological groups of comparable standing. This may partly be due to the fact that deposits of iron bacteria are readily perceived by the naked eye." Carpenter and Herndon (1933) investigated the drainage produced by bituminous coal mines on different coal seams. They reported some waters were alkaline or near neutrality, whereas others were very acid, and suggested that the reaction responsible for the production of the acid waters was:

Experiments on photoreactivation of bacteriophages inactivated with ultraviolet radiation

Abstract: Kelner (1949), working with conidia of Streptomyces griseus, discovered that light belonging to the visible range is capable of reactivating biological material that has been rendered inactive by ultraviolet radiation (UV). Shortly after Kelner's discovery was known, a similar phenomenon in bacteriophages (bacterial viruses) was observed by accident. Plates of nutrient agar containing UV-inactivated phage and sensitive bacteria had been left for several hours on a table illuminated by a fluorescent lamp. After incubation it was noticed that the number of plaques was higher on these plates than on similar plates incubated in darkness. A short report of this phenomenon of "photoreactivation" (PHTR) has already been published (Dulbecco, 1949). The present paper contains the results of a first group of experiments concerning PHTR of seven bacteriophages of the T group active on Escherichia coli, strain B.

Persistence of individual strains of escherichia coli in the intestinal tract of man

Abstract: There is ample evidence that man invariably acquires E8cherichia coli during the first day or two of life, if not, indeed, even before birth, and that he is never thereafter without it. The constancy of this occurrence makes it a safe presumption that every day throughout life new strains of this organism are introduced into the intestinal tract. If all strains established themselves there and multiplied with equal facility, one would expect that the strain composition of the E. coli of the feces of any individual over a period of time would present an exceedingly complicated and constantly changing picture. There are so many unknown factors involved in this picture, however, that inferences are of little value unless supported by observed facts. For most organisms there would be no way to study the strain composition of material containing them, but the great antigenic diversity of E. coli offers an opportunity to determine at least whether the number of strains present at any one time is small or large and whether individual strains tend to persist over long periods or whether their tenure is very brief. Two studies have been made in recent years that throw some light on this subject. Kauffmann and Perch (1943) studied two persons over a period of approximately 4 months, plating out stool specimens from each at irregular intervals, selecting 2 to 4 colonies from each plate and classifying them with respect to their 0 groups. The results from one of their subjects revealed one to three different antigenic groups in each specimen. In only one instance was the same group found in two specimens, and in this case the interval between its first and last appearance was so long (90 days) as to suggest that it more likely represented the appearance of a new strain of the group than the persistence in the bowel of the original one. Their other subject, however, yielded the same antigenic group in each of 10 successive specimens collected over a period of 42 days, together with occasional more transient groups, and after its disappearance another group appeared in 3 successive specimens collected during a period of 58 days. Waliick and Stuart (1943) made a study on a single subject, collecting specimens at more frequent and more regular intervals and picking 10 colonies from each specimen. Their study continued over a period of 15 months and revealed a more or less definite pattern in the E. coli strain composition of the feces of the individual studied. Three of their antigenic groups were almost continuously present for several months each, but not concurrently, though there was some overlapping. Along with these, in most specimens, there appeared from one to three others that were either not found at all in later specimens or in only a few successive

Some effects of hydrostatic pressure on the multiplication and morphology of marine bacteria.

Abstract: Hydrostatic pressure in the sea, which increases approximately 0.1 atmosphere per meter of depth, appears to be a factor that influences bacterial activities. This was indicated by the observations of Certes (1884a,b), Certes and Cochin (1884), and Regnard (1884a,b). The reports of Chlopin and Tammann (1903), Hite et al. (1914), Larson et al. (1918), and more recent ones reviewed by Macheboeuf et al. (1933), Cattell (1936), and Basset et al. (1938) indicate that the critical pressure tolerance of microorganisms ranges from 3,000 to 12,000 atmospheres, which is higher than pressures characteristic of the greatest known depth of the sea, the latter being of the order of 1,100 atmospheres. The apparent discrepancies are probably due to differences in experimental conditions, including growth phase, species, culture medium, temperature, time, and other factors now known to influence the pressure tolerance of microorganisms. ZoBell and Johnson (1949) found that many common microorganisms from surface soil and shallow water were killed in the logarithmic phase of growth in 48 hours at 30 C by pressures of only 500 to 600 atmospheres, and multiplication of some microorganisms was inhibited at 300 atmospheres. Resting cells, endospores, and bacteria from the deep sea were found to be more pressuretolerant as were organisms pressurized at higher temperatures. The term \"barophilic\" was coined to describe organisms that grow preferentially or exclusively at high hydrostatic pressures. Such bacteria have been found in the deep sea and also in brines from deep oil wells. Their counterparts that grow only at relatively low pressures, say up to 200 atmospheres, are described as \"barophobic.\" Those that tolerate high pressures but grow best at normal pressures are described as \"baroduric.\" The present paper is concerned primarily with observations on the occurrence and behavior of barophilic, barophobic, and baroduric bacteria in the sea.

Ion antagonisms in microorganisms: interference of normal magnesium metabolism by nickel, cobalt, cadmium, zinc, and manganese

Abstract: In the course of studies of the effect of trace elements on the metabolism of Escherichia coli, Aerobacter aerogenes, Torulopsis utilis, and Aspergillus niger, toxic effects of nickel, cobalt, cadmium, zinc, and manganese became apparent. Further investigation showed that some of these effects were influenced by the magnesium level in the medium and that low magnesium concentrations led to heightened toxicity of the foregoing divalent cations. Numerous in vitro studies have established the role of magnesium as an activator of enzyme systems. This element, in some cases replaceable by Mn++, Zn++, Cd+, Co++, and NiW, is known to be a coenzyme in reactions involving phosphate transfer (Bamann and Heumuller, 1940; Utter and Werkman, 1942). Most of these elements are known to be of importance in the action of dipeptidases (Johnson and Berger, 1942; Smith, 1949). These elements also are of importance as activators of oxalacetic decarboxylase (Krampitz and Werkman, 1941; Herbert, 1950). Magnesium and potassium have been recognized as the two cations essential for almost all forms of life. In the case of E. coli these two cations alone will support fair growth with a small amount of iron being helpful but not essential (Waring and Werkman, 1944; Young, 1944). Olson and Johnson (1949) have investigated the cation requirements of Torulopsis utilis. In addition to potassium and magnesium they have obtained good evidence of zinc, iron, and copper requirements. Steinberg (1935) has studied extensively the cation requirements of A&pergillus niger. In addition to the well-known need for potassium and magnesium he has found that small amounts of iron and zinc are essential for good growth. Manganese, copper, and gallium produce a definite but small growth response. Attention has been focused on cobalt because it is a constituent of vitamin B12, which is essential to the metabolism of some organisms.

Chromatin staining of bacteria during bacteriophage infection.

Abstract: Infection of bacteria with bacteriophage, leading to bacterial lysis, must be accompanied by changes in cell organization that should be recognizable by cytological examination. Since bacteria contain desoxyribosenucleic acid (DNA) localized in discrete \"chromatinic bodies,\" and since DNA is one of the major components of all phages thus far analyzed, chromatin stains should yield valuable information. Preliminary work on this problem (Luria and Palmer, 1946) was considered worth extending with improved technique (Robinow, 1944). A brief report of observations similar to those described in the present article has been published by Beumer and Quersin (1947). A different appearance of the chromatinic material in uninfected and lysogenic strains of Bacillus megatherium has also been described (Ehrlich and Watson, 1949). Boyd (1949) has observed specific morphological changes in Escherichia coli B after infection with phages of the T group by means of phase-contrast microscopy, a method that unfoItunately yields no cytochemical information.

The effective concentrations of penicillin in vitro and in vivo for streptococci, pneumococci, and Treponema pallidum

Abstract: In the therapeutic use of penicillin, the question as to whether the minimum effective concentration in vivo is the same, greater, or less than that necessary to kill the same organ'sm in vitro is of obvious importance. Data are here reported with respect to the minimal effective serum concentrations of penicillin in a number of experimental infections in mice and rabbits. As will be shown, these serum levels were usually 2 to 5 times higher than those necessary to kill the same organism in vitro. However, in view of the known concentration differential between the serum and tissue fluids, this suggests that the effective concentration of penicillin at the actual site of infection is in most instances the same as that effective in vitro.

The periodic acid-Schiff stain for the demonstration of fungi in animal tissue.

Abstract: The routine histopathologic stains used for the demonstration of fungi in animal tissue are inadequate. The fungi are differentiated poorly and sometimes not at all. This is a limitation in the diagnosis of the mycotic granulomas in which the organisms may be rare. A definitive fungus stain, therefore, is needed, particularly by the pathologist and mycologist. During an attempt to stain the capsules of certain fungi, brilliant staining with the periodic-acid-Schiff-reagent technique (Hotchkiss-McManus stain) was observed. A survey of many different types of mycotic tissue revealed the general usefulness of this reaction in mycologic histopathology. The present communication presents the method and briefly reviews the pertinent literature. The chemistry of this and related reactions has been recently reviewed by DeLamater, Mescon, and Barger (1950). The various applications of the Schiff reagent have in common the requirement that the tissues must be hydrolyzed in such a manner as to release substances (usually aldehydes) that will recolorize and react with the Schiff reagent. The best known use of the Schiff reagent is in the Feulgen reaction, which is presujmably specific for aldehydes released from desoxyribonucleic acid by acid hydrolysis of the tissue. Under optimal conditions the nuclei only stain. The Bauer stain calls for prolonged hydrolysis of tissue in chromic acid (Lillie, 1947a). Under these conditions glycogen stains intensely red with the Schiff reagent. The Bauer reaction is an empirical procedure (Hotchkiss, 1948). Potassium permanganate or other oxidizing agents can be substituted for the chromic acid in the hydrolyzing process. How this may affect the chemical specificity of the reaction is not yet clear. It is not possible to predict from the chemical structure which substances will recolorize with the Schiff reagent. The chemistry of the periodic-acid-Schiff technique is fairly well understood (Hotchkiss). The substances stained by this procedure belong to the general class of carbohydrates. These must contain the 1,2-glycol grouping in unsubstituted form or the equivalent structure in which OH groups are replaced by amino or alkylamino groups. Jeanloz (1950), however, has stated that he believes structure has no definite relation to a positive reaction. Periodic acid

The isolation and cultivation of lactobacillus bifidus: a comparison of branched and unbranched strains

Abstract: Lactobacillus bifidus (\"B. bifidus\") was first described, by Tissier (1899), as constituting almost the entire flora of the stools of breast-fed infants. In subsequent publications (1905, 1906, 1908), he found that the predominating organism in the stools of bottle-fed infants was Lactobacillus acidophilus (\"B. acidophilus\"), which, however, was first isolated, also from nurslings' stools, by Moro (1900). Tissier (1905) and Moro (1905) agreed that L. acidophilus was present in the feces of breast-fed infants in small numbers. Interest in the isolation and growth requirements of L. bifidus was stimulated by its apparently unique occurrence in the stools of nurslings since it was surmised that the presence of these organisms in the intestines was of physiologic significance and might prevent intestinal disorders caused by other bacteria. The original observations of Tissier concerning the predominance of L. bifidus in nurslings' stools have been amply confirmed. However, the factors responsible for the establishment and maintenance of this bacterial flora in the colon of the breast-fed infant are still unknown. As seen in smears of stools, the organisms are gram-positive, straight or curved rods that are nonmotile and that do not form spores. One end may be bulbous or racket-shaped. One or both ends may appear to be split longitudinally to give the effect of two short branches. This appearance led to the term \"bifid.\" Short lateral branches may also be present. On repeated subculture, the organisms isolated by Tissier lost their bifid structure and became unbranched rods. This has been the experience of many other investigators. Although L. bifidus appears to be a strict anaerobe on primary isolation, it is not generally agreed whether bifidus is a strict or a facultative anaerobe on subculture. Although the similarity of L. bifidus to diphtheroids and actinomycetes has often been noted, most workers consider that the organisms are true lactobacilli. Weiss (1933) and Weiss and Rettger (1934), who thoroughly reviewed the literature, undertook a systematic study of L. bifidus, which on subculture was likewise unbranched. The writers concluded that L. bifidus and L. acidophilus are so closely related that they are probably variants of the same species. The Orla-Jensens and Winther (1936) disagreed with this claim because they could not substantiate a relationship between their \"Bact. bifidum,\" which was a branched organism, and L. acidophilus. Most of their strains, however, were isolated from the feces of adults on an ordinary diet. Subsequently Orla-Jensen (1943) concluded

Identification of the koch-weeks bacillus (hemophilus aegyptius)

Abstract: During a field investigation of acute conjunctivitis in the lower Rio Grande Valley of Texas bacteriological cultures were made from more than 100 cases. Bacteria of the genus Hemophilus, apparently the main cause of the infection, were isolated from the conjunctiva of approximately one-half of the cases. Some strains were readily identified as Hemophilus influenzae. The majority, although resembling H. influenzae in some respects, were found to be different from it and to be like the so-called Koch-Weeks bacillus described by early investigators (Koch, 1883; Weeks, 1886, 1887; and others). The relation of the Koch-Weeks bacillus and H. influenzae has been the subject of much controversy and the two have been grouped as one species by many workers. In this paper the characteristics of the Koch-Weeks bacillus and ways of separating it from H. influenzae will be presented. While investigating cholera in Egypt, Koch (1883) observed very small bacilli in the pus from the eyes of individuals having a benign form of conjunctivitis. Culturing was not attempted. Weeks (1886, 1887) was the first to culture and describe adequately a bacillus from acute contagious conjunctivitis, which is generally considered to be the same as that observed microscopically by Koch. Morax (1894), Kamen (1899), and others confirmed these findings and made additional observations. An extensive review of the literature up to 1907 is given by Axenfeld (1908). In 1887 Kartulis observed a similar organism in a film and claimed cultivation on blood serum and agar-agar. His description of the cultured organism varies somewhat from that of others, and it has been considered by Morax (1894), Weeks (1895), Axenfeld (1908), and Ali (1926) that he cultured an associated organism. Unfortunately Kartulis' description was widely used for the KochWeeks bacillus in early classifications of bacteria (Kruse, 1896; Chester, 1897, 1901; Migula, 1900). This has complicated the selection of the species name that has priority. Shortly after Pfeiffer (1892) observed the influenza bacillus, Morax and Beach (1896) noted that its colonies and those of the Koch-Weeks bacillus were similar, but they considered that the organisms were different. Kamen (1899) noted further similarity and concluded that they should be placed in the same group. In a review by Axenfeld (1908) and in one by Knorr (1924c) divergent conclusions were reached. Axenfeld concluded that the bacteria differed in morphology, in

Cytological Changes in Escherichia coli produced by Infection with Phage T2.

Abstract: The bacteriophages of the \"T\" system acting on Escherichia coli have beein studied extensively anti have provided a considerable basis for theory of the mechanism and processes of a virus infection. Although methods have been developed for the detailed cytological study of bacterial cells, studies of phageinfected bacteria by such methods have been infrequent. Preliminary experiments by Luria and Palmer (1946) and by Beeumer and Quersin (1947) demonstrate the fruitfulness of this line of attack. They showved that each phage produces modifications in the internal structure of the infected cell peculiar to the race of phage and not to the strain of host cells and, further, that these studies \"indicate an intimate relation between this process and the behavior of the Feulgenpositive nucleoprotein bodies of the bacterial cell\" (Luria and Palmer, 1946). Confirmation and extension of this work is important for two reasons: (1) The correlation of structural changes during phage infection with chemical and metabolic changes (such as t-hose reviewved by Cohen, 1947, 1949) should be of value. (2) Attempts to define the mechanism of reproduction of phage by means of electron microscope studies (e.g., Wyckoff, 1948; Merling, 1949) wvould be aided by cytological and chemical data as a basis for the control and the interpretation of structures. Studies using phase microscopy (such as those of Boyd, 1949a,b) should be similarly integrated. A further return may well be a better understanding of the structure or arrangement of the normal nucleus, since a great part of the change early in phage infection is reflected in alterations in the nucleus of the bacterial cell. As an approach to this problem it was decided to study first the sequence of changes to be observedl in E. coli infected with the T2 phages, since a great volume of published data has accumulated for this particular system. The results are presented in this paper.

The relation of ion antagonism to the inorganic nutrition of lactic acid bacteria

Abstract: During a study of the specificity of the requirement of Lactobacillus arabinosus for Mn++, it was observed that ZnH was toxic for this organism and that its toxicity could be overcome by increasing the concentration of Mn++ in the medium. In addition to Mn++, several inorganic ions not previously implicated in the nutrition of these bacteria were found to counteract the Zn+ inhibition. The same ions also exerted a sparing action on the Mn+ requirement of this organism. These and related observations are presented below. An explanation of the observed antagonistic effects is offered based on the assumption that Zn++ inhibits growth by interfering with the formation of one or more metabolically essential metalloproteins from certain proteins (apoenzymes) of the cell and that those ions that counteract the inhibition do so by forming active complexes with these same proteins. This explanation represents an extension of the theory of competitive analogue-metabolite antagonism to ion antagonism in bacteria

The cytology of an avian strain of Mycobacterium tuberculosis studied with the electron and light microscopes.

Abstract: The early literature on the cytology of M1ycobacterium tutbercuilosis was reviewe(I by Knaysi (1929). Among the reports not reviewed by him are those of Feinberg (1900), Nakanishi (1901), 'Minder (1916), Kirchensteins (1922), and Petit (1926). Feinberg observed a red nucleus and a bluie cytoplasm in cells stainedl by a modified Romanowski's soluition. iNakanishi demonstrated by postvital staining wi-ith methylene blute a round body locatedl near the middle of the cell; sometimes there was a constricted body or there were two round bodies. 'Minder distinguished between MIuch's granules and polar bodies, although the latter w-ere demonstrable by Mluch's method of staining. He stated that the grantules w-ere neither spores nor decomposition products. Kirchensteins, using a complicated method of staining with basic fuchsin, concluded that a nuclear apparattus existed consisting of several granules united by fine filaments. Petit did not attribute to the granules a nuclear nature. Knaysi (1929) studiedI a strain, originally of the human type, which had lost its pathogenicity; his observations were summarized as follows:

A comparison of the immunogenicity of weakly encapsulated and of strongly encapsulated strains of Cryptococcus neoformans (Torula histolytica).

Abstract: This paper deals with a comparison of the antibody-evoking capacities (in rabbits) of weakly encapsulated and of strongly encapsulated cells of Cryptococcus neoformans and with the influence of the number of the fungus cells (amount of vaccine) upon the strength and the promptness of the antibody response. The data on these two points contribute toward a better understanding of the immunogenic properties of this fungus and, in addition, present an instance in which antibodies reactive with the large capsules of strongly encapsulated forms of a species were produced more effectively by immunization with weakly encapsulated forms than by immunization with the strongly encapsulated forms of the species. The prevailing impression that Cryptococcus antiserums are difficult or inconvenient to produce has come from the fact that a number of workers failed with all strains tried, others failed with some strains although succeeding with others, and all who have reported the production of reasonably potent antiserums have employed prolonged series of injections over periods ranging from 64 to 12 weeks. The literature consists of the papers of Stoddard and Cutler (1916), Sheppe (1924), Rappaport and Kaplan (1926), Benham (1935), Cox and Tolhurst (1946), Kligman (1947), Drake (1948), and Evans (1949). Most of the authors give no information either on the degree of encapsulation or on the density of the Cryptococcus suspensions employed for the immunizations. Cox and Tolhurst (1946), and also Evans (1949), have reported differences in the immunogenic effectiveness of different strains but did not mention any differences in encapsulation. Kligman (1947) did describe differences in encapsulation of the test strains, but his results (with immunizing procedures much different than the one we will describe) were uniformly negative with a weakly, an intermediate, and a strongly encapsulated strain. Textbooks and literature reviews commonly state that a high degree of encapsulation is responsible for the reportedly poor immunogenicity of this fungus. However, there has been little, if any, experimental evidence. The opinions expressed are always based (when any supporting reference is given) upon the results Benham (1935) obtained by immunization with Cryptococcus cells that had been allowed to stand (presumably at room temperature) for 14 hours in the presence of 0.05 N HCl. Benham (1935) does not actually state what effect this

A turbidimetric method for the assay of antibiotics

Abstract: Turbidimetric assay procedures for antibiotic substances have been proposed by Foster (1942); McMahan (1944); Lee, Foley, and Epstein (1944); and Joslyn (1944). Standard methods for the assay of penicillin and streptomycin are used by the Food and Drug Administration (Federal Register, 1947, and recent revisions) and by manufacturers of these antibiotics. Not one of these procedures is exactly applicable to the assay of antibiotic materials for which no standards have been established.

Some additional nutritional requirements of certain lactic acid bacteria

Abstract: As a result of extensive previous work, the nutritional requirements of many lactic acid bacteria are known in considerable detail. Most of the presently known B vitamins and amino acids are required by one or another of the organisms of this group, and such organisms have been extensively applied to the quantitative determination of these substances (reviews: Snell, 1948, 1950). Despite this large area of information, many lactic acid bacteria still cannot be grown in the absence of crude materials that supply nutritive substances of undefined nature (Rogosa, Tittsler, and Geib, 1947; Kitay, McNutt, and Snell, 1950). In addition to amino acids and the better known B vitamins, isolated representatives of this group of organisms have been shown recently to require unsaturated fatty acids (Hutchings and Boggiano, 1947; Williams, Broquist, and Snell, 1947), pyridoxamine phosphate (McNutt and Snell, 1948, 1950), lactose (Snell, Kitay, and Hoff-Jorgensen, 1948; Shapiro, Rhodes, and Sarles, 1949), vitamin B12 (e.g., Shorb, 1948; Skeggs et al., 1948), and various desoxyribosides (Kitay, McNutt, and Snell, 1949, 1950; McNutt and Snell, 1950; Hoff-Jorgensen, 1949). In addition to these pure compounds, unidentified growth factors such as the LactobaciUus bulgaricus factor (Williams, Hoff-Jorgensen, and Snell, 1949) and the Leuconostoc citrovorum factor (Sauberlich and Baumann, 1948) are essential for certain strains of lactic acid bacteria. In view of these results, a survey was undertaken to determine the requirement of about thirty strains of lactic acid bacteria for these newly discovered growth factors. All of these organisms, which belonged to seven different species, failed to grow in media lacking certain supplements discussed above. Results showing the requirement of several of these cultures for vitamin B12 or for various desoxyribosides, and conditions under which this requirement is eliminated by reducing agents, were presented and discussed by Kitay, McNutt, and Snell (1950). Additional information relative to other nutritional requirements is discussed below.

The transformation of typhoid bacilli into L forms under various conditions.

Abstract: That L type cultures can be isolated from Salmonella typhosa and many other bacterial species on agar plates containing high concentrations of penicillin was reported in previous papers (Dienes, 1948a,b, 1949). Transformation into L forms was observed under various other conditions. It often occurred as a result of spontaneous autolysis of cultures (Dienes, 1942). In Proteus, refrigeration of the cultures, antagonism between strains, and exposure to tap water resulted in the development of these forms (Dienes, 1949). The study of the conditions inducing L transformation has extended over many years. The behavior of various bacilli and cocci was studied in the presence of bacteriostatic agents and after exposure to injuries that bacteria encounter in their natural life. Since the studies in Proteus were reported, most significant observations have been made in S. typhosa. In this species L forms developed upon exposure of the bacilli to various types of chemical injuries, to antibody and complement, and to bacteriophage. Observations relating to the conditions in which typhoid bacilli were transformed into L forms are presented in this paper. In the following paper the characteristics of Salmonella L type cultures, including S. typhosa, wil be described. The behavior of six freshly isolated typhoid strains was studied on penicillin plates. All behaved similarly and produced abundant L type colonies, which grew without difficulty in subcultures. It was previously mentioned (Dienes, 1948a) that an old laboratory strain produced L type colonies poorly. The medium and techniques most advantageous for the production of Proteus L forms also were most favorable for typhoid; however, more uniform results were obtained by using anaerobic incubation in the typhoid experiments. Anaerobic incubation is also necessary for the maintenance of typhoid L strains in subcultures. The conditions essential for the growth of typhoid L type cultures in the presence of penicillin are the following: the agar must be soft (the usual nutrient agar should be diluted with 50 to 100 per cent broth); the medium must contain 10 to 20 per cent animal serum; and, as in the case of Proteus, horse serum obtained from defibrinated blood is superior to human serum or ascitic fluid. L type colonies were rarely obtained with rabbit serum and never with mouse