Bacteriophages for Aeromonas salmonicida were isolated from water and mud samples taken from 13 of 19 trout hatcheries and ponds examined in southern Ontario. Nine of the 13 locations were known to have histories of furunculosis disease. The bacteriophages studied formed three serological groups and two distinct morphological types. Phages of serological groups I and II possessed similar morphology; those of group III resembled the coli T-even phages. All possessed complex symmetry consisting of a head and tail with a contractile tail sheath. Latent periods of the phages ranged from 35 to 95 min and average burst sizes from 21 to 193. A group I phage and a group III phage had [Formula: see text] values of 351 and 1000, respectively.

Electron microscopy of infection threads and bacteria in young root nodules of Medicago sativa. J. Bacteriol. 86:125-137. 1963.-Ultrathin sections of alfalfa nodules (Medicago sativa L.

Light and electron microscopic studies on the effect of fasting and exercise on lipids in the pectoralis muscle of the pigeon have revealed considerable increase in intracellular as well as extracellular lipids (1) in fasted pigeons and (2) in normal and fasted pigeons when the muscle of one side was electrically stimulated for different periods of time. Similar increase in lipids was also seen in the contralateral quiescent muscle. These observations were confirmed by bioehemical assays of the lipid content in the muscle under identical experimental conditions. It is concluded that the intracellular muscle lipids are not immediately drawn upon for energy either during exercise or fasting as long as there is ready supply of lipids transported through the blood stream from external sources such as adipose tissue.It was also observed that the inflow of lipids into the muscle was to, the fat-utilizing red fibers and not the glycogen-utilizing white fibers, which, even normally, contain no- intracellular lipid inclusions. The intracellular transport of lipids in muscle, therefore, may be considered a selective process. The mitochondria of both types of fiber in the exercised muscle appeared to be swollen.

Certain elongate elements that occur in special structures (mycetomes, made up of constituent mycetocytes) in the larvae of the granary and rice weevils (Sitophitrus granarius (L.) and Sitophilus oryza (L.)) have long been regarded as microorganisms; and there is some evidence that they are of benefit but not essential to the insect host. These elongate elements are also found in the guts and female gonads of adult insects. The elements have resisted all efforts to culture them and thus, while they have been generally regarded as microorganisms, their exact biological status has been open to doubt. Electron micrographs, it is claimed, have now established them as undoubtedly microorganisms.

No intracellular infection threads were observed in ultrathin sections of young root nodules of lupine, although nodule bacteria could be found in the intercellular spaces between the root cortical cells. Evidence suggests that in certain instances the plant cell walls can be disrupted locally, allowing the bacteria to pass into cytoplasm of the host cell. The spread of infection may be initiated in this manner and extended by division of infected cells. No plant-produced enclosing membranes were present around bacteria in the intercellular spaces but such structures developed after the bacteria had entered the plant cell. Although the origin of these membranes is debatable, in the present work it appeared that they were formed de novo, perhaps in a manner akin to the development of the cell plate during cell division. Most of the bacterial cells possessed a wide subwall space lying between the bacterial cell wall and plasma membrane. Discontinuities present in the latter membrane may account for the ribosome-like material found in the subwall space.