The acsD gene is involved in cellulose biosynthesis among the Acetobacter species. In the current study, we created an acsD disruption mutant in the acsABCD cellulose synthase operon of Gluconacetobacter xylinus and characterized the resulting cellulose to aid in providing insight into the function of the acsD gene. Both the wild type G. xylinus AY201 (derivative of Gluconacetobacter hansenii ATCC 23769) and the acsD disruption mutant produced crystalline cellulose I microfibrils. The cellulose produced by both appeared to be synthesized from an aggregate of pores known as a linear terminal complex; however the total cellulose synthesized was 10 % that of the wild type G. xylinus AY201. TEM observations of the acsD disruption mutant confirmed that microfibrils and bundles of microfibrils were similar in size to the G. xylinus AY201 wild type; however, the final ribbon dimensions were narrower (53.4 ± 13.1 nm wt, vs. 28.2 ± 8.2 nm). Additional TEM observations of the mutant cells incubated at 4°C revealed an abnormal linear terminal complex orientation whereby the resulting band material could be observed in a transverse orientation as well as longitudinally to the long axis of the cell. Taken together, these data strongly suggest that acsD aids in the proper orientation of the linear terminal complexes along the longitudinal axis of the cell indicating the AcsD protein is involved in the final level of the hierarchical assembly of cellulose resulting in highly efficient cellulose synthesis.
This study reports the release of the complete nucleotide sequence of Gluconacetobacter hansenii strain NQ5 (ATCC 53582). This strain was isolated by R. Malcolm Brown, Jr. in a sugar mill in North Queensland, Australia, and is an efficient producer of bacterial cellulose. The elucidation of the genome will contribute to the study of the molecular mechanisms necessary for cellulose biosynthesis.
The cellulose producer and model organism used for the study of cellulose biosynthesis, Gluconacetobacter hansenii AY201, is a variant of G. hansenii ATCC 23769. We report here the complete nucleotide sequence of G. hansenii AY201, information which may be utilized to further the research into understanding the genes necessary for cellulose biosynthesis.
A UHF/VHF beacon receiver located in Helwan, Egypt, frequently observes structures in ΔTEC/Δt measurements (where TEC is total electron count), where the F region (300 km) intercept of the radio rays crosses the steep topographic gradients associated with the Anatolian Plateau. There are three classes of structures: bumps, ripples and waves. A bump is defines as a single spatial ΔTEC/Δt peak with a peak‐to‐trough amplitude of at least 0.01 TECU/s (1 TEC unit (TECU) = 1016 electrons/m2) that is at least 1° wide in F region latitude. A ripple is a bump with smaller structures on either side of the central bump. Finally, waves have amplitudes ≥0.01 TECU/s with several roughly equal peaks. These features were observed repeatedly in a number passes from 31 August to 30 November 2008. Over half of passes had either a bump (34.6%), a ripple (18.2%) or a wave (6.3%). Most of these structures occur near areas with large orographic gradients. The prevailing surface wind blows across the mountains when bumps and ripples are observed. These correlations suggest that the local ionosphere is affected by the ground topography, most likely through the orographic lifting and the associated gravity waves.
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