Isolation and identification of low density polythene-degrading bacteria from soil of North West of Algeria

Plas c bags (Low Density Polyethylene (LDPE) belong to the polymers, which plays a very important role in our daily lives by their diversi ed applica on. However, the accumula on of the plas c bags in the environment cons - tutes a serious problem and a real source for visual nuisance, pollu on of soil and marine environments. Furthermore, their biodegradation was the safest method of breakdown that possibly leaves behind less toxic residues and showed poten al of bio-geo chemical cycling of the substrate. The aim of the present work was the characterization of the isolated bacterial strains from a municipal land ll area of Tlemcen, North West Algeria, which were implicated by the biodegrada on ability of the Low Density Polyethylene. The degradation of the Low Density Polyethylene was inves gated by studying the bacterial growth of the isolated, inoculated on a solid culture medium, which was composed of LDPE as the sole carbon source with and with- out a nitrogen source and the selec on was based by the determination of the produced diameter of hydrolysis clear zone on the surface. Furthermore, the isolated, selected degrading Low Density Polyethylene bacterial ML002 has been iden ed by the study of their morphological, biochemical charac- teris cs and the ampli ca on of the fragment, coding the region of ARN 16S. The use of the API system indicated their belonging to the genus Bacillus Cereus, which has reduced the weight of LDPE by 0.26, 1.28, 1.53% a er 30, 90, 120 days respec vely. Furthermore, the amplified of the fragment, coding the region of ARN 16S by the isolated, selected bacterial ML002 indicated a similarity of 99.394% with Bacillus wiedmannii and Bacillus proteolyticus and 99.293% homology with Bacillus toyonensis, Bacillus cereus and Bacillus thuringiensis. </jats:p

An active dimanganese(III)-tyrosyl radical cofactor in Escherichia coli class Ib ribonucleotide reductase

Escherichia coli class Ib ribonucleotide reductase (RNR) converts nucleoside 5′-diphosphates to deoxynucleoside 5′-diphosphates and is expressed under iron-limited and oxidative stress conditions. This RNR is composed of two homodimeric subunits: α2 (NrdE), where nucleotide reduction occurs, and β2 (NrdF), which contains an unidentified metallocofactor that initiates nucleotide reduction. nrdE and nrdF are found in an operon with nrdI, which encodes an unusual flavodoxin proposed to be involved in metallocofactor biosynthesis and/or maintenance. Ni affinity chromatography of a mixture of E. coli (His)[subscript 6-]NrdI and NrdF demonstrated tight association between these proteins. To explore the function of NrdI and identify the metallocofactor, apoNrdF was loaded with Mn[superscript II] and incubated with fully reduced NrdI (NrdI[subscript hq]) and O[subscript 2]. Active RNR was rapidly produced with 0.25 ± 0.03 tyrosyl radical (Y·) per β2 and a specific activity of 600 units/mg. EPR and biochemical studies of the reconstituted cofactor suggest it is Mn[superscript III][subscript 2-]Y·, which we propose is generated by Mn[superscript II][subscript 2-]NrdF reacting with two equivalents of HO[subscript 2]−, produced by reduction of O[subscript 2] by NrdF-bound NrdI[subscript hq.] In the absence of NrdI[subscript hq], with a variety of oxidants, no active RNR was generated. By contrast, a similar experiment with apoNrdF loaded with Fe[superscript II] and incubated with O[subscript 2] in the presence or absence of NrdI[subscript hq] gave 0.2 and 0.7 Y·/β2 with specific activities of 80 and 300 units/mg, respectively. Thus NrdI[subscript hq] hinders Fe[superscript III][subscript 2-]Y· cofactor assembly in vitro. We propose that NrdI is an essential player in E. coli class Ib RNR cluster assembly and that the Mn[superscript III][subscript 2-]Y· cofactor, not the diferric-Y· one, is the active metallocofactor in vivo.National Institutes of Health (U.S.) (Grant number GM81393)National Defense Science and Engineering Graduate Fellowshi