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Decreased Growth Rates (decreased + growth_rate)
Selected AbstractsBiodesulfurization of dibenzothiophene using recombinant Pseudomonas strainJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2008Lavanya Meesala Abstract BACKGROUND: The sulfur content in crude oil available from various sources ranges from 0.03 to values as high as 8.0 wt%. These high quantities of sulfur must be removed before the crude oil is processed because combustion of this oil would result in severe environmental pollution, such as acid rain. Due to high utility and operating costs, the conventional hydrodesulfurization process (HDS) is considered to be uneconomic. The biotechnological option, biodesulfurization (BDS) seems an attractive low cost, environmentally benign technology. RESULTS: This paper reports the development of a recombinant strain of bacteria designed by introducing desulfurizing, dsz genes containing plasmid pSAD 225-32, which was isolated from Rhodococcus erythropolis IGTS8 into a gram negative solvent-tolerant bacterium, Pseudomonas putida (MTCC 1194). This recombinant bacterium can desulfurize the dibenzothiophene (DBT) in the sulfur selective 4S-pathway. It has been observed that for the same concentration of DBT, the recombinant strain's growth rate is greater than that of the parent strain. Increasing the concentration of DBT resulted in an increase of lag phase as well as decreased growth rate, which shows that the bacteria is following substrate inhibition type kinetics. This genetically modified bacterium can desulfurize 73.1% of 1.2 mmol L,1 DBT (dissolved in ethanol) in 67 h of cultivation time using growing cells. CONCLUSIONS: It is concluded that further research in this area of biodesulfurization using genetically modified organisms may remove the bottlenecks presently in the way of commercialization of the BDS process. Copyright © 2007 Society of Chemical Industry [source] Is Escherichia coli getting old?BIOESSAYS, Issue 8 2005Conrad L. Woldringh Whether or not bacteria divide symmetrically, the inheritance of cell poles is always asymmetrical. Because each cell carries an old and a new pole, its daughters will not be the same. Tracking poles of cells and measuring their lengths and doubling times in micro-colonies, Stewart et al.1 observed that growth rate diminished in cells inheriting old poles and concluded that these cells are susceptible to aging. Here, their results are compared with studies on the variabilities of length and age at division. It is argued that the decreased growth rate in old pole cells falls within the expected variation and may therefore be sufficiently far from a catastrophe-like cell death through aging. BioEssays 27:770,774, 2005. © 2005 Wiley Periodicals, Inc. [source] Mutagenesis of ,-tubulin cysteine residues in Saccharomyces cerevisiae: Mutation of cysteine 354 results in cold-stable microtubulesCYTOSKELETON, Issue 2 2001Mohan L. Gupta Jr. Abstract Cysteine residues play important roles in the control of tubulin function. To determine which of the six cysteine residues in ,-tubulin are critical to tubulin function, we mutated the cysteines in Saccharomyces cerevisiae ,-tubulin individually to alanine and serine residues. Of the twelve mutations, only three produced significant effects: C12S, C354A, and C354S. The C12S mutation was lethal in the haploid, but the C12A mutation had no observable phenotype. Based on interactive views of the electron crystallographic structure of tubulin, we suggest that substitution of serine for cysteine at this position has a destabilizing effect on the interaction of tubulin with the exchangeable GTP. The two C354 mutations, although not lethal, produced dramatic effects on microtubules and cellular processes that require microtubules. The C354 mutant cells had decreased growth rates, a slowed mitosis, increased resistance to benomyl, and impaired nuclear migration and spindle assembly. The C354A mutation produced a more severe phenotype than the C354S mutation: the haploid cells had chromosome segregation defects, only 50% of cells in a culture were viable, and a significant percentage of the cells were misshapened. Cytoplasmic microtubules in the C354S and C354A cells were longer than in the control strain and spindle structures appeared shorter and thicker. Both cytoplasmic and spindle microtubules in the two C354 mutants were extremely stable to cold temperature. After 24 h at 4°C, the microtubules were still present and, in fact, very long and thick tubulin polymers had formed. Evidence exists to indicate that the C354 residue in mammalian tubulin is near the colchicine binding site and the electron crystal structure of tubulin places the residue at the interface between the ,- and ,-subunits. The sulfhydryl group is situated in a polar environment, which may explain why the alanine mutation is more severe than the serine mutation. When the C12S and the two C354 mutations were made in a diploid strain, the mutated tubulin was incorporated into microtubules and the resulting heterozygotes had phenotypes that were intermediate between those of the mutated haploids and the wild-type strains. The results suggest that the C12 and C354 residues play important roles in the structure and function of tubulin. Cell Motil. Cytoskeleton 49:67,77, 2001. © 2001 Wiley-Liss, Inc. [source] Bacteria divert resources from growth for magellanic penguin chicksECOLOGY LETTERS, Issue 6 2002Jaime Potti Abstract The influence of bacteria on the growth of their wild avian hosts is unknown. We tested experimentally whether administration of a wide-spectrum antibiotic (cephalosporine) during early development of magellanic penguin (Spheniscus magellanicus) chicks had any effect on their growth rates in the wild. Chicks that were injected in two occasions with cephalosporine grew faster than control untreated chicks. The positive effect of medication on nestling growth disappeared after the treatment ceased, did not alter haematological indices indicative of health status, had no influence on chick survival until near independence and was related to a changed bacterial composition of the faecal microbiota of treated chicks when compared with that from control chicks. These results were similar to those obtained for poultry with antimicrobials promoting growth and chick nutrient assimilation rates. Gram-positive bacilli in the diphtheroid genus Corynebacterium are likely candidates to cause decreased growth rates in magellanic penguin chicks. [source] Effects of tail autotomy on survival, growth and territory occupation in free-ranging juvenile geckos (Oedura lesueurii)AUSTRAL ECOLOGY, Issue 4 2006JONATHAN K. WEBB Abstract Many animals autotomize their tails to facilitate escape from predators. Although tail autotomy can increase the likelihood of surviving a predatory encounter, it may entail subsequent costs, including reduced growth, loss of energy stores, a reduction in reproductive output, loss of social status and a decreased probability of survival during subsequent encounters with predators. To date, few studies have investigated the potential fitness costs of tail autotomy in natural populations. I investigated whether tail loss influenced survival, growth and territory occupation of juvenile velvet geckos Oedura lesueurii in a population where predatory snakes were common. During the 3-year mark,recapture study, 32% of juveniles voluntarily autotomized their tails when first captured. Analysis of survival using the program mark showed that voluntary tail autotomy did not influence the subsequent survival of juvenile geckos. Survival was age-dependent and was higher in 1-year-old animals (0.98) than in hatchlings (0.76), whereas recapture probabilities were time-dependent. Growth rates of tailed and tailless juveniles were very similar, but tailless geckos had slow rates of tail regeneration (0.14 mm day,1). Tail autotomy did not influence rock usage by geckos, and both tailed and tailless juveniles used few rocks as diurnal retreat sites (means of 1.64 and 1.47 rocks, respectively) and spent long time periods (85 and 82 days) under the same rocks. Site fidelity may confer survival advantages to juveniles in populations sympatric with ambush foraging snakes. My results show that two potential fitness costs of tail autotomy , decreased growth rates and a lower probability of survival , did not occur in juveniles from this population. However, compared with juveniles, significantly fewer adult geckos (17%) voluntarily autotomized their tails during capture. Because adults possess large tails that are used for lipid storage, the energetic costs of tail autotomy are likely to be much higher in adult than in juvenile O. lesueurii. [source] | |||||||||||||||||||