The B. mycoides N host-virus system. I. Differences in appearance and "rate of growth" of the lysogenic and parent indicator strains

There were differences in the way the lysogenic strain N of B. mycoides and the parent indicator strain grew on nutrient agar and in nutrient broth. 1. On agar, the indicator culture traveled more quickly over the agar surface than the phage-carrying strain; the total extent of spread was greater. 2. In broth, the indicator strain grew diffusely throughout the liquid, the lysogenic cells in clumps. The virus-infected strain appeared to grow more slowly. This may reflect (a) the effect of aggregation on the generation time of the lysogenic strain, (b) an active lytic process in the lysogenic population which is further enhanced by the effect of clump formation on the environment of the cell.     

Ribonuclease and Other Factors Involved in the Respiratory Senescence of Maize Scutellum

The scutella from seedlings of Zea mays L. germinated at 28–30°C increase in respiration rate to the third day, followed bya decline which is quite noticeable by the fifth day. A searchhas been made for factors responsible for the respiratory decline.The electronmicroscope shows the five-day mitochondria to benormal in appearance. Very active preparations are obtainedby isolating the mitochondria at pH 7.6 with inclusions of bovineserum albumin and ethylenediamine-tetraacetic acid. A solubleribonuclease (RNase A) which increases rapidly with age impairsboth oxidation and phosphorylation. The largely particle-boundribonuclease (RNase B) is not inhibitory. Plant ribonucleaseis resistant to the proteolysis occurring during senescence.It is suggested that the soluble ribonuclease contributes tothe respiratory decline, but that other factors may also beinvolved.     

The B mycoides N host-virus system. II. Interrelation of phage growth,bacterial multiplication,and lysis in infections of the indicator strain of B. mycoides N with phage N in nutrient broth

In nutrient broth at 30 to 32°C., the cycle of virus growth (following adsorption) in lag phase cells of B. mycoides N included a period of intracellular multiplication, ranging from 0.8 to 1.3 hours, succeeded by a sharp rise in the free phage titer and then by a slower rise or a plateau in the extracellular phage content. The yield of virus per infected cell at 30°C., as determined by a modified Burnet dilution technique, was about 76 plaque-forming particles. During the latent period, multiply infected cells showed no change in numbers. Coinciding with phage release, incomplete clearing occurred. The unlysed, remaining cells multiplied and the turbidity rose again. These survivors and their progeny were lysogenic.     

The action of air ions on bacteria. I. Protective and lethal effects on suspensions of Staphylococci in droplets

Techniques have been devised for studying quantitatively the effects of air ions on microorganisms suspended in small drops. In smog-contaminated atmospheres moderate concentrations of positive and negative air ions exerted a protective effect on staphylococci by delaying the drop in pH customarily observed and by diminishing the rate of evaporation. In clean air higher concentrations of positive and negative air ions accelerated the rate of death of staphylococci apparently by direct action on the cells and by increasing the rate of evaporation. Air ion action in these experiments did not involve cell agglutination or direct radiation from the radioactive isotopes employed.     

Alewife planktivory controls the abundance of two invasive predatory cladocerans in Lake Michigan

1. We sampled along a nearshore transect (10-m bathymetric contour) in Lake Michigan to determine diet, 24-h feeding periodicity, daily ration and food requirements of an invasive fish, the alewife, Alosa pseudoharengus , relative to zooplankton abundance and production. Our objective was to determine whether the alewife controls the abundance of two invasive, predatory cladocerans, Bythotrephes longimanus and Cercopagis pengoi .
2. Bosminidae was the most abundant prey taxon and Chydoridae, Leptodora , Chironomidae and Bythotrephes were the least abundant. Neither Bythotrephes nor Cercopagis were important prey for small alewives (≤100 mm). Bythotrephes was eaten by over 50% of large alewives (>100 mm) and accounted for 10–27% of the diet weight. Cercopagis was eaten by about 30% of the large alewives but only accounted 1% of the diet weight.
3. Food weight in stomachs was highest early in the night for small alewives and lowest at night for large alewives. Chironomidae and large Chydoridae were the preferred prey of small alewives. Bythotrephes and large Chydoridae were the preferred prey for large alewives.
4. Food requirements of alewife were much less than production for most prey taxa, although the consumption of Bythotrephes greatly exceeded production on both dates. Alewives consumed only 3% of Cercopagis production. High selectivity and food requirements of alewife for Bythotrephes , and low selectivity and food requirements for Cercopagis , probably explain the difference in abundance between these two invasive cladocerans at our nearshore site in Lake Michigan.     

Parameters of gaseous ion effects on the mammalian trachea. A. Duration of effects. B. Minimal effective ion densities

A. Duration of Effects Groups of mice exposed to high densities of unipolar light air ions for 72 hours exhibited persistent alterations in the functional efficiency of their tracheas. These effects lasted at least 4 weeks, and in the case of animals treated with (+) ions included diminished ciliary activity, pale and contracted tracheal mucosa, and enhanced vulnerability to trauma. Following treatment with (-) ions, animals displayed increased ciliary activity with no other detectable changes. It required at least 60 minutes of exposure to ions to induce such "permanent" functional changes. B. Minimal Effective Ion Densities The minimal ion densities producing changes in ciliary activity within an arbitrary period of 30 minutes were determined with extirpated tracheal strips from rabbits and guinea pigs. The threshold value for (-) ions was approximately 2.5 x 10³ ions/cm.²/sec. and that for (+) ions was in the range between 1 x 10⁴ and 2.5 x 10⁵ ions/cm.²/sec.The minimal ion densities producing changes in ciliary activity within an arbitrary period of 30 minutes were determined with extirpated tracheal strips from rabbits and guinea pigs. The threshold value for (-) ions was approximately 2.5 x 10³ ions/cm.²/sec. and that for (+) ions was in the range between 1 x 10⁴ and 2.5 x 10⁵ ions/cm.²/sec. The evidence indicates that ion-induced functional changes in the ciliated epithelium of the pulmonary tree are the results of direct contact of ions with surface cells and do not involve participation of the central nervous system or circulation. So far as ciliary activity is concerned, the number of ions required to produce a change in rate is very small.     

The lytic action of tyrothricin and its derivatives on Staphylococcus aureus

A tyrothricin concentration of 0.01 mg. per ml. causes rapid lysis of Staphylococcus aureus; this lyric action is not enhanced by phage. A concentration of 0.001 mg. per ml. of tyrothricin is likewise capable of lysing staphylococci, and the addition of phage does not appreciably alter the rate of lysis. A concentration of 0.0001 mg. per ml. of tyrothricin is unable to effect lysis though it enhances the lytic activity of phage. The tyrocidine fraction of tyrothricin appears to be responsible for the latter's lytic action.     

The effect of iodoacetate and other inhibitors on phage production and lysis in three phage systems

The minimal bacteriostatic concentration of iodoacetate, azide, or proflavine was added at intervals during the latent periods of virus in three different bacterium-bacteriophage systems (M. aureus, B. mycoides, E. coli). For each interval at which inhibitor was added, the occurrence of lysis and the final yield of phage were determined. In the B. mycoides and E. coli systems, when added during the first part of the latent period, inhibitor prevented lysis and no phage was released. Introduction of inhibitor during the last part of the latent period resulted in normal lysis and in a linear increase in phage that progressively approached the yield obtained in the absence of inhibitor (the later the introduction, the higher the yield). In the M. aureus system, phage production and lysis in the presence of inhibitor followed the same general pattern, except that release of phage and normal lysis occurred in infected cells to which inhibitor had been added quite early in the latent period. Our results, when compared with those of Foster (1948) with proflavine and Bozeman et al. (1954) with chloramphenicol, suggest that (1) the final phage yields represent the amount of mature intracellular virus present at the time of addition of inhibitor and (2) the reactions leading to lysis proceed independently of those leading to the formation of mature virus once phage infection has reached a critical point in time.