Reversion of the gal3 mutation of Escherichia coli: Partial deletion of the insertion sequence

Summary The gal3 mutation of E. coli is an insertion of a DNA sequence, 1,100 base pairs in length, into the operator-promoter region of the galactose operon. This mutation reverts spontaneously to gal⁺ by excision of the insertion to produce stable, inducible revertants, or by tandem duplications of the gal operon to produce unstable, constitutive revertants. The nature of a third class of revertants, which are stable and constitutive, is the subject of the present study.The stable, constitutive class of revertants included approximately 30% of all gal⁺ revertants obtained from a gal3() strain. Although the constitutive reversions could be transduced by , the efficiency was found to be extremely poor and the rare transductants which did appear seemed to originate from abnormal transducing particles. It was concluded that these reversions were not normally packaged by .In order to facilitate the packaging of these reversions, the chlD-pgl region was deleted from the parent gal3() strain. Unexpectedly, the gal3 mutation in the majority of these deletions reverted to produce stable, constitutive reversions exclusively. The explanation proposed was that the chlD-pgl deletions had also removed part of the gal operator-promoter up to the gal3 insertion, so that simple excisions of the insertion yielded stable, constitutive revertants by connecting the gal structural genes to a different promoter. These revertants were not considered to be true representatives of the stable, constitutive class. The specificity of deletion end-points at the insertion was found only in the gal3() strain, and not in gal ⁺, gal ⁺(), or gal3 strains. Moreover, the frequency of spontaneous chlD-pgl deletions increased 10- to 15-fold in presence of the gal3 insertion.A gal phage bearing a true stable, constitutive reversion (gal ^c 200) was isolated from the revertant strain by subsequent deletion of the chlD-pgl segment (31). Electron micrographs of gal ⁺ and gal ^c 200 31(chlD pgl) DNA heteroduplexes were interpreted to indicate that the stable, constitutive reversion had arisen by a deletion of 3/4 of the gal3 insertion sequence.The main conclusions are: (i) the stable, constitutive reversions of gal3 can arise by partial deletions of the insertion sequence, apparently by elimination of the nucleotide sequence which causes polarity; (ii) the chlD-pgl deletions may exhibit preferential termination at the right extremity of the gal3 insertion in presence of prophage ; and (iii) the gal3 insertion appears to inhibit the production of gal particles by providing a nucleotide sequence which is recognized and degraded by a specific endonuclease. It is suggested that inhibition of transducing particle formation by gal3 and the preferred termination of deletions at gal3 might represent related phenomena.     

Acetophenone and stilbene derivatives from Gnetum ula

The isolation of bergenin, 2-hydroxy-4-benzyloxyacetophenone and the related dimer and stilbene from Gnetum ula is reported.     

Non-Communicable Disease Risk Factors among Employees and Their Families of a Saudi University: An Epidemiological Study

ObjectivesTo assess the prevalence of noncommunicable disease (NCD) risk factors among Saudi university employees and their families; to estimate the cardiovascular risk (CVR) amongst the study population in the following 10years.MethodsThe NCD risk factors prevalence was estimated using a cross-sectional approach for a sample of employees and their families aged ≥ 18 years old, in a Saudi university (Riyadh in Kingdom of Saudi Arabia; KSA). WHO STEPwise standardized tools were used to estimate NCD risk factors and the Framingham Coronary Heart Risk Score calculator was used to calculate the CVR.ResultsFive thousand and two hundred subjects were invited, of whom 4,500 participated in the study, providing a response rate of 87%. The mean age of participants was 39.3±13.4 years. The majority of participants reported low fruit/vegetables consumption (88%), and physically inactive (77%). More than two thirds of the cohort was found to be either overweight or obese (72%), where 36% were obese, and 59% had abdominal obesity. Of the total cohort, 22–37% were found to suffer from dyslipidaemia, 22% either diabetes or hypertension, with rather low reported current tobacco use (12%). One quarter of participants was estimated to have >10% risk to develop cardiovascular disease within the following 10-years.ConclusionThe prevalence of NCD risk factors was found to be substantially high among the university employees and their families in this study.     

Studies on the antibacterial effects of negapillin in combination with other antibiotics and sulfa drugs

Summary The antibacterial effect of negapillin in combination with other antibiotics and sulfa drugs was studied using Gram+ve and Gram-ve bacteria as test organisms. Subsequently, various proportions of negapillin in combination with the antibiotics and the sulfa drugs were examined to determine the optimum proportions which exert maximum inhibitory effects on the bacterial growth. Mixtures of these antibiotics with negapillin were found more superior not only as antimicrobial agents but also for having comparatively low toxicity.     

High incidence of asymptomatic cases during an outbreak of Plasmodium malariae in a remote village of Malaysian Borneo

An outbreak of Plasmodium malariae occurred in Sonsogon Paliu village in the remote area of Ulu Bengkoka sub-district of Kota Marudu, Northern Sabah, Malaysian Borneo from July through August 2019. This was the first outbreak of malaria in this village since 2014. On 11^th July 2019 the Kota Kinabalu Public Health Laboratory notified the Kota Marudu District Health Office of a Polymerase Chain Reaction (PCR) positive case of P. malariae. This index case was a male from Sulawesi, Indonesia working for a logging company operating in Sonsogon Paliu. During the resulting outbreak, a total of 14 symptomatic cases were detected. All of these cases were positive by thick and thin blood smear examination, and also by PCR. During the outbreak, a mass blood survey screening was performed by light-microscopy and PCR. A total of 94 asymptomatic villagers 31 (33.0%) were PCR positive but thick and thin blood smear negative for P. malariae. Both symptomatic and asymptomatic cases received treatment at the district hospital. When symptomatic and asymptomatic cases were considered together, males (29/45. 64.5%) were infected more than females (16/45, 35.6%), the male:female ratio being 1.8:1. Adults were the predominant age group infected (22/45, 48.9%) followed by adolescents (19/45, 42.2%) and children under five years of age (4/45, 8.9%). This report illustrates that symptomatic and submicroscopic cases pose a challenge during P. malariae outbreaks and that PCR is a valuable tool for their identification. The rapid identification and control of imported malaria is crucial for the continued control of malaria in Malaysia.