Transductional evidence for plasmid linkage of lactose metabolism in streptococcus lactis C2.

A lactose-negative (Lac-), proteinase-negative (Prt-) mutant, designated C145 was isolated from Streptococcus lactis C2 after treatment with nitrosoguanidine and ultraviolet irradiation. The mutant appeared to be cured of the prophage(s) present in S. lactis C2 based on non-inducibility by ultraviolet irradiation or mitomycin C. When cleared lysate material from C145 was subjected, to cesium chloride-ethidum bromide (EB) density gradient centrifugation, no plasmid peak was observed, suggesting that C145 was cured of plasmid deoxyribonucleic and (DNA). A histogram showing distribution of contour lengths of circular molecules of DNA from C145, however, revealed the presence of a greatly diminished number of DNA molecules as compared with the parent culture and indicated the absence of the 30 x 10(6) plasmid. Cesium chloride-ethidium bromide gradient profiles from Lac+, Prt- and Lac+ Prt+ transductants of C145 revealed no plasmid peak, but electron microscopy of the fractions normally possessing the satellite band of DNA showed the presence of a new plasmid species having a molecular weight from 20 x 10(6) to 22 x 10(6). This plasmid was lost when the transductants became Lac-. Examination of a plasmid histogram from a spontaneous Lac- Prt- mutants of S. lactis C2 resembled that of C145, with the absence of the 30 x 10(6) plasmid and the presence of the 22 x 10(6) plasmid in Lac+ Prt+ transductants. The results suggest that lactose metabolism is mediated through the 30 x 10(6) plasmid in S. lactis C2 and that the transducing bacteriophage, which is too small to accommodate the entire plasmid, is transferring about two-thirds of the original plasmid through a process termed transductional shortening.     

Studies on phosphoglyceromutase from chicken breast muscle: number and reactivity of sulfhydryl groups.

Phosphoglyceromutase (PGM) from chicken breast muscle was titrated with p-mercuribenzoate (PMB), 5,5'-dithiobisnitrobenzoate (Nbs2), N-ethylmaleimide (NEM), iodoacetate and iodoacetamide. The effect of all of the sulfhydryl reagents, with the exception of NEM was to cause a loss in enzymatic activity. Addition of KCN following reaction with Nbs2 resulted in the recovery of a small amount of enzymatic activity. In the absence of substrate (3-phosphoglyceric acid) or cofactor (2,3-diphosphoglyceric acid) and in the presence or absence of 6 M guanidine hydrochloride, six sulfhydryl groups per mole of enzyme were titrated with PMB.     

A Revision of the Cytology and Ontogeny of Several Deficiencies in the 3a1–3c6 Region of the X Chromosome of DROSOPHILA MELANOGASTER

The cytology and developmental attributes of 18 deficiency mutations in the 3A1–3C6 region of the salivary gland X chromosome of Drosophila melanogaster have been investigated. The cytological limits of several older deficiencies have been revised and clarified and several new deficiencies are characterized. The deficiency mutants, with one possible exception, show a lethal phase in the late embryonic period or the early first larval instar. In contrast, the earliest acting point mutation lethals exposed by these deficiencies generally exhibit a somewhat later, post-embryonic lethality, perhaps indicating that the deficiencies are having some cumulative or synergistic impact on development. However, even with this difference in time of lethality, it is still possible to conclude that it is not the absolute size of the deficiency but rather the character of the loci deleted that determines the impact on development. Observations on the morphology of lethal embryos shows that while this analysis is internally consistent, it does not agree with earlier work. None of the 3A1–3C6 deficiencies causes any major teratologies during embryogenesis. Furthermore, the "earliest acting" gene in this region does not lie in band 3C1 but is most likely associated with bands 3A8–10.     

Life on Mars

Abstract

There is evidence that at one time Mars had liquid water habitats on its surface. Studies of microbial communities in cold and dry environments on the Earth provide a basis for discussion of the possible nature of any life that may have existed on Mars during that time. Of particular relevance are the cyanobacterial communities found in hypolithic and endolithic habitats in deserts. Microbial mats found under ice-covered lakes provide an additional possible Martian system. Results obtained from these field studies can be used to guide the search for fossil evidence of life on Mars. It is possible that in the future life will be reintroduced on Mars in an effort to restore that planet to habitable conditions. In this case the organisms under study as exemplars of past life may provide the hardy stock of pioneering Martian organisms. These first organisms must be followed by plants. The feasibility of reviving Mars will depend on the ability of plants to grow in an abundance of CO₂ but at extremely low pressures, temperatures, O₂, and N₂ levels. On Mars, biology was, and is, destiny.     

Direction of Temperature Control in the Thermal Biofeedback Treatment of Vascular Headache

In order to test for the specific therapeutic effects of thermal biofeedback (TBF) for hand warming on vascular headache (HA), 70 patients with chronic vascular HA were randomly assigned to TBF for hand warming, TBF for hand cooling, TBF for stabilization of hand temperature, or biofeedback to suppress alpha in the EEG. Patients in each condition initially had high levels of expectation of therapeutic benefit and found the treatment rationales highly credible. Participants in each condition received 12 treatment sessions on a twice-per-week basis. Based on daily HA diary data gathered for 4 weeks prior to treatment and 4 weeks after treatment, HA Index was significantly (p=.003) reduced as was HA medication consumption. There were no differential reducations in HA Index or Medication Index among the four conditions. Global self-reports of improvement gathered at the end of the post-treatment monitoring period also did not differ among the four conditions. We were unable to demonstrate a specific effect of TBF for hand warming on vascular HA activity.     

Plant Glycoprotein biosynthesis Uridine diphosphate N-acetyl-glucosaminyltransferase from horseradish root

A particulate enzyme preparation from horseradish root tissue was shown to catalyze the transfer of 2-acetamido-2-deoxy-d-[¹⁴C₁]glucose from uridine diphosphate 2-acetamido-2-deoxy-d-[¹⁴C₁]glucose to an exogenous acceptor molecule derived from horseradish peroxidase. The acceptor was produced from purified peroxidase by the action of a mixture of glycoside hydrolases covalently bound to Sepharose. The membrane preparation containing the transferase was purified approximately 12-fold by aqueous two phase distribution and by discontinuous sucrose density gradient centrifugation.Hydrolysis of the reaction product yielded glucosamine as the only radiolabeled substance. Precipitation of the reaction product by antiserum against peroxidase showed that the label was incorporated into peroxidase. The transferase utilized the acceptor most efficiently when only 12% of the 2-acetamido-2-deoxy-d-glucose was removed from the acceptor. The acceptor lost no accepting capabilities when heated to 100°C for 3 min prior to assay. Trypsin treatment caused a 14% decrease in label incorporated while pronase treatment caused a 93% decrease.     

Generation of a highly attenuated strain of Pseudomonas aeruginosa for commercial production of alginate

Alginate is an important polysaccharide that is commonly used as a gelling agent in foods, cosmetics and healthcare products. Currently, all alginate used commercially is extracted from brown seaweed. However, with environmental changes such as increasing ocean temperature and the increasing number of biotechnological uses of alginates with specific properties, there is an emerging need for more reliable and customizable sources of alginate. An alternative to seaweed for alginate production is Pseudomonas aeruginosa, a common Gram-negative bacterium that can form alginate-containing biofilms. However, P. aeruginosa is an opportunistic pathogen that can cause life-threatening infections in immunocompromised patients. Therefore, we sought to engineer a non-pathogenic P. aeruginosa strain that is safe for commercial production of alginate. Using a homologous recombination strategy, we sequentially deleted five key pathogenicity genes from the P. aeruginosa chromosome, resulting in the marker-free strain PGN5. Intraperitoneal injection of mice with PGN5 resulted in 0% mortality, while injection with wild-type P. aeruginosa resulted in 95% mortality, providing evidence that the systemic virulence of PGN5 is highly attenuated. Importantly, PGN5 produces large amounts of alginate in response to overexpression of MucE, an activator of alginate biosynthesis. The alginate produced by PGN5 is structurally identical to alginate produced by wild-type P. aeruginosa, indicating that the alginate biosynthetic pathway remains functional in this modified strain. The genetic versatility of P. aeruginosa will allow us to further engineer PGN5 to produce alginates with specific chemical compositions and physical properties to meet different industrial and biomedical needs.     

Turbid reefs moderate coral bleaching under climate‐related temperature stress

Thermal‐stress events that cause coral bleaching and mortality have recently increased in frequency and severity. Yet few studies have explored conditions that moderate coral bleaching. Given that high light and high ocean temperature together cause coral bleaching, we explore whether corals at turbid localities, with reduced light, are less likely to bleach during thermal‐stress events than corals at other localities. We analyzed coral bleaching, temperature, and turbidity data from 3,694 sites worldwide with a Bayesian model and found that K_d490, a measurement positively related to turbidity, between 0.080 and 0.127 reduced coral bleaching during thermal‐stress events. Approximately 12% of the world's reefs exist within this “moderating turbidity” range, and 30% of reefs that have moderating turbidity are in the Coral Triangle. We suggest that these turbid nearshore environments may provide some refuge through climate change, but these reefs will need high conservation status to sustain them close to dense human populations.