Ichtyotoxic activity of extracts from Mexican marine macroalgae

Seventy-three species of macroalgae from the Mexican Pacific, Atlantic and Caribbean coast were screened for ichtyotoxic activity. Ethanolic, acetonic and aqueous extracts were prepared and tested against the fish Carassius auratus. The extracts were classified on the basis of their effects as: toxic if the fish died in two hours or less; moderately toxic, if the organism behaved abnormally but death did notoccur, and non-toxic if the fish did not display any change. 79% species were ichtyotoxic to some degree. Extracts of 39 species were toxic, with at least one extract with lethal effects, 19 were moderately toxic and 15 species were non-toxic. Only the extracts ofDictyota bartayresiana, Dictyota cervicornis,Lobophora variegata, Bryothamnion triquetrum and Laurencia obtusa were toxic in all three solvents. The acetone and ethanol extracts were more active, and therefore are more suitable for extraction of toxic substances. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of uracil on colonial morphology ofNeisseria gonorrhoeae

The production of cells ofNeisseria gonorrhoeae that form type-T4 colonies in cultures started with cells that originally formed only type-T2 colonies was inhibited by calf thymus RNA. Guanosine and uracil were the only nucleic acid constituents that significantly reduced the T2 to T4 shift. Uracil gave the best results in degree of inhibition. It was found that some tritiated uracil was incorporated into the RNA of growing cells ofN. gonorrhoeae but that much more was incorporated into DNA probably after conversion to guanine and adenine. The data show that the shift from T2 to T4 can be progressively inhibited by increasing the concentration of uracil in the growth medium.     

Effect of culture conditions on synthesis of L-asparaginase by Escherichia coli A-1.

The nutritional requirements and culture conditions affecting biosynthesis of L-asparaginase in a mutant of Escherichia coli HAP designated strain A-1 were studied. Asparaginase activity was increased by the addition of L-glutamic acid, L-glutamine, or commercial-grade monosodium glutamate. The rate of enzyme synthesis was dependent on the interaction between the pH of the culture and the amount of oxygen dissolved in the medium. A critical oxygen transfer rate essential for asparaginase formation was identified, and a fermentation procedure is described in which enzyme synthesis is controlled by aeration rate. Enhancement of L-asparaginase activity by monosodium glutamate was inhibited by the presence of glucose, culture pH, chloramphenicol, and oxygen dissolved in the fermentation medium.     

HLA antigens in a sample of the Spanish population: Common features among Spaniards,Basques, and Sardinians

Summary Frequencies of recently described HLA-A,-B (antigens or splits) and HLA-C and HLA-DR antigens are studied in a 450 normal Spaniards sample. The linkage disequilibria are also calculated. HLA-DR7 is more frequent than in any other population studied. Aw30-B18 and Aw33-B14 associations are common and specific Spanish, Basque, and Sardinian HLA features. A11-B27 association is found in our Spanish sample and also in Basques.HLA-Bw4,-Bw6 antigens are analyzed by family mating and segregation and also using unrelated individuals. It shows a good fit as a genetic system. HLA-B antigens are included either in Bw4 or Bw6 according to expectations from other Caucasoid population results. The possibility of a common and North African origen (Iberians) for Spaniards, Basques, and Sardinians is discussed on the basis of presently available HLA data.     

Interstitial deletion (2)(p13p15)

Summary A dysmorphic 5-year-old girl with severe growth and mental deficiency was studied. She presented a de novo interstitial 2p deletion. Karyotype: 46,XX,del(2)(p13p15).     

Phosphate-limited culture of Azotobacter vinelandii.

Batch cultures of Azotobacter vinelandii grown in phosphate-deficient media were compared with control cultures grown in phosphate-sufficient media. Phosphate limitation was assessed by total cell yield and by growth kinetics. Although cell protein, nucleic acids, and early growth rate were unaffected by phosphate deficiency, cell wall structure, oxygen uptake, and cell viability were significantly affected. Also, phosphate-limited cells contained much larger amounts of poly-beta-hydroxybutyric acid but lower adenylate nucleotide energy charge than did control cells. The ratio of adenosine 5'-triphosphate to adenosine 5'-diphosphate was much lower in phosphate-deficient cells. The data indicate a substrate saving choice of three metabolic pathways available to this organism under different growth conditions.     

Mechanism of lethal action of 2,450-MHz radiation on microorganisms.

Various bacteria, actinomycetes, fungi, and bacteriophages were exposed to microwaves of 2,450 +/- 20 MHz in the presence and in the absence of water. It was found that microorganisms were inactivated only when in the presence of water and that dry or lyophilized organisms were not affected even by extended exposures. The data presented here prove that microorganisms are killed by "thermal effect" only and that, most likely, there is no "nonthermal effect"; cell constituents other than water do not absorb sufficient energy to kill microbial cells.     

Genome Sequences of Burkholderia sp. Strains CCGE1002 and H160, Isolated from Legume Nodules in Mexico and Brazil

The genome sequences of Burkholderia sp. strains CCGE1002 from Mexico and H160 from Brazil, isolated from legume nodules, are reported. Their gene contents in relation to plant-microbe interactions and xenobiotic degradation are discussed.