Salt-containing Medium Research Articles

Schistosoma mansoni: Protein phosphorylation during transformation of cercariae to schistosomula

Infectivity of the multicellular pathogen Schistosoma mansoni for the human host is dependent upon the ability of free-living cercariae to transform rapidly into parasitic schistosomula. The biochemical pathways that regulate this transitional period are unknown. The role of protein phosphorylation was investigated by examining the incorporation of [32Pi]phosphate into proteins of S. mansoni. A sevenfold increase in total phosphorylation was found in 3-hr-old schistosomula as compared to cercariae. Analysis of radiolabeled proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography demonstrated that a 14-kDa protein served as a marker for transformation, being phosphorylated in schistosomula but not cercariae. The protein was phosphorylated on a serine residue. Phosphorylation was stimulated by a shift of parasites from water to salt-containing medium at 23 degrees C. Incubation of organisms in water at 37 degrees C did not initiate phosphorylation of this protein. The 14-kDa phosphoprotein was extracted from parasite homogenates with 1 M NaCl but was insoluble in 1% Triton X-100. Protein phosphorylation during the cercarial-schistosomula transformation may represent an important biochemical event that regulates infectivity of the parasite for the human host.

Studies on the Wittig Reaction (V) Trans Stereoselectivity in the Reaction of Benzylidene Alkyl Diphenylphosphorane and Aldehydes

Abstract In previous papers, we reported the E-selectivity in the Wittig reaction of phosphorus ylid of the general formula Ph2R′CH2P=CHR (R=alkenyl; R′=H, alkenyl) and aldehydes. This continuing research for the stereochemistry of diphenylphosphorane in the title reaction of Ph2R′CH2P=CHR and R″CHO, where R=Ph, R′=H,Ph and R″=Ph,p-substituted phenyl, has led to thosimilar results. However, the E-selectivity is dependent on the ylid structure, reaction condition and the nature of the substituents on the aromatic ring. Generally the effect is stronger with benzyl diphenylphosphorane(R=H), the proportion of E olefin is produced in a larger quantity in salt-free condition than in the salt-containing medium, and the aromatic aldehyde bearing an electronwithdrawing group on the ring gives a higher E/Z ratio. Moreover, we also found that the logarithms of the E/Z ratio of the substituted stilbene products are linear with the σ constant of the substituents of the aromatic aldehydes: log E/Z=aσ+ b

Isolation and characterization of 22 mesophilic methanococci

Twenty-two strains of mesophilic methanococci were isolated from salt marsh and other intertidal sediments of the southeastern United States. All the isolates were irregular cocci between 1 and 3 um in diameter, lysed rapidly in distilled water or 0.01% sodium dodecyl sulfate, used H 2 + CO 2 and formate as energy sources, and grew rapidly in salt-containing medium. The mol % G+C of six of the isolates was between 29.2 and 31.5. These isolates resembled Methanococcus voltae and required acetate, isoleucine, and leucine for growth. The mol % G+C of the remaining 16 isolates was between 32.6 and 34.4. They all grew autotrophically in mineral medium. The growth rates of eight of the autotrophic isolates were stimulated by either acetate or casamino acids. Although these isolates resembled several species of the genus Methanococcus , it was not possible to assign them to a species.

Proteins Produced during Salt Stress in Tobacco Cell Culture

The protein pattern of cultured tobacco (Nicotiana tabacum L. var Wisconsin 38) cells that have become adapted to a medium containing 10 grams NaCl per liter was compared to that of unadapted cells on one-dimensional sodium dodecyl sulfate gels. Two protein bands (32,000 and 20,000 daltons) were much more abundant in the salt-adapted cells, and one protein (26,000 daltons) was unique to the salt cells. This protein pattern did not change during the growth cycle of the cells. When salt-adapted cells are transferred to control medium, their ability to grow in the salt-containing medium returns to that of control cells after one passage in the control medium (Hasegawa, Bressan, Handa 1980 Plant Cell Physiol 21: 1347). Within this time the levels of the 32,000 and 20,000 dalton proteins also return to that of the control cells, but the 26,000 dalton protein does not disappear until after at least two passages in control medium. Amino acid analyses of these three proteins revealed that they all contain some hydroxyproline.

Death and injury of Staphytococcus aureus during thermal treatment of milk.

Staphylococcus aureus isolated from milk and grown in milk was heated in milk. The phenomena of death as well as injury was investigated in the range of 50 to 75 degrees C. The D60 value (decimal reduction time on salt-free medium) was 0.87 min, the D'60 value (decimal reduction time in salt-containing medium) was 0.62 min. Cultures were injured as soon as heating started. This initial thermal shock increased with increasing temperature. At 50-60 degrees C injury was more rapid than death. At greater than 60 degrees C death became faster than injury and the two processes coincided at 70 degrees C. The Z value was 9.46 degrees C and the Z' value was 9.93 degrees C.