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951.
Paul G. McDonald Catherine F. Heathcote Michael F. Clarke Jonathan Wright Anahita J. N. Kazem 《Journal of avian biology》2007,38(1):113-121
Acoustically-mediated individual discrimination has been the focus of much investigation in ornithology. For cooperatively breeding species, strong selection pressure favouring individual recognition during acts of altruism is predicted under many of the most interesting hypotheses proposed to account for helping behaviour. We investigated differences in 157 calls given by 12 different individuals as they provisioned nestlings, including both breeding and helper bell miners Manorina melanophrys (Meliphagidae), a cooperatively breeding honeyeater endemic to south-eastern Australia. Individual differences were apparent in all 15 call parameters analysed, many with a high level of repeatability. Moreover, the information capacity of mew calls allows as many as 515 different signatures to exist in the system. As many parameters showed strong sex differences, separate discriminant functions were used to predict individual identity within each sex. Five parameters were used in a function that correctly identified over 90% of female calls in both a training (n = 35) and test dataset (n = 11) not used to generate the function. Among males, a separate function used six parameters to correctly assign individual identity in 89.3% (n=84; training) and 77.8% (n=27; test) of cases. Three original parameters, including spectral and spatial characteristics, were highly correlated with functions predicting identity in both sexes. The accuracy of functions was not influenced by a signaller's sex, breeding status, or by sampling period which was spread over as much as two breeding seasons within individuals. Significant potential therefore exists for bell miners to use these simple provisioning calls in individual discrimination. If this is the case, call information also has the potential to be used by receivers as predicted by signalling hypotheses proposed to account for cooperative helping behaviour, such as the pay-to-stay and social prestige hypotheses. 相似文献
952.
Soline Vigneau Florence Levillayer Herv Crespeau Laurence Cattolico Bernard Caudron Franck Bihl Catherine Robert Michel Brahic Jean Weissenbach Jean-Franois Bureau 《Genomics》2001,78(3):206-213
We sequenced a 173-kb region of mouse chromosome 10, telomeric to the Ifng locus, and compared it with the human homologous sequence located on chromosome 12q15 using various sequence analysis programs. This region has a low density of genes: one gene was detected in the mouse and the human sequences and a second gene was detected only in the human sequence. The mouse gene and its human orthologue, which are expressed in the immune system at a low level, produce a noncoding mRNA. Nonexpressed sequences show a higher degree of conservation than exons in this genomic region. At least three of these conserved sequences are also conserved in a third mammalian species (sheep or cow). 相似文献
953.
Michel Petitprez Catherine Caumont Henri Barthou Michel Wright Gilbert Alibert 《Physiologia plantarum》2001,111(1):102-107
The cytoskeleton is involved in major developmental events in plant cell growth and differentiation. Nucleation events play a key role in the dynamic and organization of the microtubule (Mt) cytoskeleton. Among many proteins involved in Mt nucleation, γ -tubulin has been identified as an essential component of the Mt organizing centers (MTOC). In protoplasts, somatic embryogenesis induction has been correlated with remodeling of Mt cytoskeleton. We have investigated the specific developmental expression of γ -tubulin in Helianthus annuus . Two γ -tubulin isoforms have been detected by immunoblotting, with bands at 52 and 58 kDa. The larger γ -tubulin (58 kDa) is present in all the sunflower tissues tested and is associated with the nucleus. The smaller γ -tubulin (52 kDa), differing from the former at the carboxy-terminal end, is only present in meristematic and dedifferentiated cells and is not bound to the nucleus. This first demonstration of the presence of two γ -tubulins in plant cells is discussed in terms of distinct roles in the nucleation and organization of Mts. 相似文献
954.
Thompson SA Maani EV Lindell AH King CJ McArthur JV 《Applied and environmental microbiology》2007,73(7):2199-2206
Resistances to tetracycline and mercury were identified in an environmental strain of Serratia marcescens isolated from a stream highly contaminated with heavy metals. As a step toward addressing the mechanisms of coselection of heavy metal and antibiotic resistances, the tetracycline resistance determinant was cloned in Escherichia coli. Within the cloned 13-kb segment, the tetracycline resistance locus was localized by deletion analysis and transposon mutagenesis. DNA sequence analysis of an 8.0-kb region revealed a novel gene [tetA(41)] that was predicted to encode a tetracycline efflux pump. Phylogenetic analysis showed that the TetA(41) protein was most closely related to the Tet(39) efflux protein of Acinetobacter spp. yet had less than 80% amino acid identity with known tetracycline efflux pumps. Adjacent to the tetA(41) gene was a divergently transcribed gene [tetR(41)] predicted to encode a tetracycline-responsive repressor protein. The tetA(41)-tetR(41) intergenic region contained putative operators for TetR(41) binding. The tetA(41) and tetR(41) promoters were analyzed using lacZ fusions, which showed that the expression of both the tetA(41) and tetR(41) genes exhibited TetR(41)-dependent regulation by subinhibitory concentrations of tetracycline. The apparent lack of plasmids in this S. marcescens strain, as well as the presence of metabolic genes adjacent to the tetracycline resistance locus, suggested that the genes were located on the S. marcescens chromosome and may have been acquired by transduction. The cloned Tet 41 determinant did not confer mercury resistance to E. coli, confirming that Tet 41 is a tetracycline-specific efflux pump rather than a multidrug transporter. 相似文献
955.
Stanley EC Mole RJ Smith RJ Glenn SM Barer MR McGowan M Rees CE 《Applied and environmental microbiology》2007,73(6):1851-1857
The FASTPlaqueTB assay is an established diagnostic aid for the rapid detection of Mycobacterium tuberculosis from human sputum samples. Using the FASTPlaqueTB assay reagents, viable Mycobacterium avium subsp. paratuberculosis cells were detected as phage plaques in just 24 h. The bacteriophage used does not infect M. avium subsp. paratuberculosis alone, so to add specificity to this assay, a PCR-based identification method was introduced to amplify M. avium subsp. paratuberculosis-specific sequences from the DNA of the mycobacterial cell detected by the phage. To give further diagnostic information, a multiplex PCR method was developed to allow simultaneous amplification of either M. avium subsp. paratuberculosis or M. tuberculosis complex-specific sequences from plaque samples. Combining the plaque PCR technique with the phage-based detection assay allowed the rapid and specific detection of viable M. avium subsp. paratuberculosis in milk samples in just 48 h. 相似文献
956.
Casey PG Gardiner GE Casey G Bradshaw B Lawlor PG Lynch PB Leonard FC Stanton C Ross RP Fitzgerald GF Hill C 《Applied and environmental microbiology》2007,73(6):1858-1863
Salmonella spp. infection is a major cause of gastroenteritis, with many thousands of cases reported in the European Union every year. The use of probiotics offers the potential to improve this situation. Here, we investigate the effects of oral treatment of pigs with a defined lactic acid bacteria culture mixture on both clinical and microbiological signs of Salmonella enterica serovar Typhimurium infection. Fifteen weaned pigs blocked by sex and weight were administered control milk or a mixture of five probiotic strains as either a milk fermentate or milk suspension for a total of 30 days. The mixture consisted of two strains of Lactobacillus murinus and one strain each of Lactobacillus salivarius subsp. salivarius, Lactobacillus pentosus, and Pediococcus pentosaceous. Following probiotic administration for 6 days, animals were challenged orally with serovar Typhimurium; the health of the animals and the microbiological composition of their feces were monitored for 23 days postinfection. Animals treated with probiotic showed reduced incidence, severity, and duration of diarrhea. These animals also gained weight at a greater rate than control pigs administered skim milk. Mean fecal numbers of Salmonella were significantly reduced in probiotic-treated animals at 15 days postinfection (P = 0.01). The administered probiotic bacteria improved both the clinical and microbiological outcome of Salmonella infection. These strains offer significant benefit for use in the food industry and may have potential in human applications. 相似文献
957.
Gérard P Lepercq P Leclerc M Gavini F Raibaud P Juste C 《Applied and environmental microbiology》2007,73(18):5742-5749
The microbial community in the human colon contains bacteria that reduce cholesterol to coprostanol, but the species responsible for this conversion are still unknown. We describe here the first isolation and characterization of a cholesterol-reducing bacterium of human intestinal origin. Strain D8 was isolated from a 10(-8) dilution of a fresh stool sample provided by a senior male volunteer with a high capacity to reduce luminal cholesterol to coprostanol. Cholesterol-to-coprostanol conversion by strain D8 started on the third day, while cells were in stationary phase, and was almost complete after 7 days. Intermediate products (4-cholesten-3-one and coprostanone) were occasionally observed, suggesting an indirect pathway for cholesterol-to-coprostanol conversion. Resting-cell assays showed that strain D8 could reduce 1.5 mumol of cholesterol/mg bacterial protein/h. Strain D8 was a gram-negative, non-spore-forming, rod-shaped organism identified as a member of the genus Bacteroides closely related to Bacteroides vulgatus, based on its morphological and biochemical characteristics. The 16S rRNA gene sequence of strain D8 was most similar (>99.5%) to those of two isolates of the recently described species Bacteroides dorei. Phylogenetic tree construction confirmed that Bacteroides sp. strain D8 clustered within an independent clade together with these B. dorei strains. Nevertheless, no cholesterol-reducing activity could be detected in cultures of the B. dorei type strain. Based on Bacteroides group-specific PCR-temporal temperature gradient gel electrophoresis, there was no correlation between the presence of a band comigrating with the band of Bacteroides sp. strain D8 and cholesterol conversion in 11 human fecal samples, indicating that this strain is unlikely to be mainly responsible for cholesterol conversion in the human population. 相似文献
958.
The nematode Caenorhabditis elegans provides numerous experimental advantages for developing an integrative molecular understanding of physiological processes and has proven to be a valuable model for characterizing Ca(2+) signaling mechanisms. This review will focus on the role of Ca(2+) release activated Ca(2+) (CRAC) channel activity in function of the worm gonad and intestine. Inositol 1,4,5-trisphosphate (IP(3))-dependent oscillatory Ca(2+) signaling regulates contractile activity of the gonad and rhythmic posterior body wall muscle contraction (pBoc) required for ovulation and defecation, respectively. The C. elegans genome contains a single homolog of both STIM1 and Orai1, proteins required for CRAC channel function in mammalian and Drosophila cells. C. elegans STIM-1 and ORAI-1 are coexpressed in the worm gonad and intestine and give rise to robust CRAC channel activity when coexpressed in HEK293 cells. STIM-1 or ORAI-1 knockdown causes complete sterility demonstrating that the genes are essential components of gonad Ca(2+) signaling. Knockdown of either protein dramatically inhibits intestinal cell CRAC channel activity, but surprisingly has no effect on pBoc, intestinal Ca(2+) oscillations or intestinal ER Ca(2+) store homeostasis. CRAC channels thus do not play obligate roles in all IP(3)-dependent signaling processes in C. elegans. Instead, we suggest that CRAC channels carry out highly specialized and cell specific signaling roles and that they may function as a failsafe mechanism to prevent Ca(2+) store depletion under pathophysiological and stress conditions. 相似文献
959.
Conlon JM Coquet L Leprince J Jouenne T Vaudry H Kolodziejek J Nowotny N Bevier CR Moler PE 《Regulatory peptides》2007,138(2-3):87-93
The members of the Aquarana (or Rana catesbeiana species group) form a monophyletic group comprising seven species: R. catesbeiana, Rana clamitans, Rana grylio, Rana virgatipes, Rana septentrionalis, Rana heckscheri and Rana okaloosae. Previous work has led to structural characterization of the antimicrobial peptides present in electrically-stimulated skin secretions from the first five species listed and this study presents the primary structures of orthologs from the river frog R. heckscheri and the Florida bog frog R. okaloosae. Peptidomic analysis of R. heckscheri and R. okaloosae skin secretions led to the identification of peptides with antimicrobial activity belonging to the ranalexin, ranatuerin-2, and temporin families. In addition, a peptide (GFLDIIKDTGKDFAVKILNNLKCKLAGGCPR) was isolated from R. okaloosae whose primary structure identified it as a member of the palustrin-2 family. Consistent with previous data based upon morphological analysis and comparisons of the nucleotide sequences of mitochondrial and ribosomal genes, cladistic analysis based upon a comparison of the amino acid sequences of antimicrobial peptides indicates a sister-group relationship between R. heckscheri and R. grylio and a close, but less well defined, phylogenetic relationship between R. okaloosae and R. clamitans. 相似文献
960.
Soil carbon saturation: concept,evidence and evaluation 总被引:20,自引:0,他引:20
Catherine E. Stewart Keith Paustian Richard T. Conant Alain F. Plante Johan Six 《Biogeochemistry》2007,86(1):19-31
Current estimates of soil C storage potential are based on models or factors that assume linearity between C input levels
and C stocks at steady-state, implying that SOC stocks could increase without limit as C input levels increase. However, some
soils show little or no increase in steady-state SOC stock with increasing C input levels suggesting that SOC can become saturated with respect to C input. We used long-term field experiment data to assess alternative hypotheses of soil carbon storage
by three simple models: a linear model (no saturation), a one-pool whole-soil C saturation model, and a two-pool mixed model
with C saturation of a single C pool, but not the whole soil. The one-pool C saturation model best fit the combined data from
14 sites, four individual sites were best-fit with the linear model, and no sites were best fit by the mixed model. These
results indicate that existing agricultural field experiments generally have too small a range in C input levels to show saturation
behavior, and verify the accepted linear relationship between soil C and C input used to model SOM dynamics. However, all
sites combined and the site with the widest range in C input levels were best fit with the C-saturation model. Nevertheless,
the same site produced distinct effective stabilization capacity curves rather than an absolute C saturation level. We conclude
that the saturation of soil C does occur and therefore the greatest efficiency in soil C sequestration will be in soils further
from C saturation.
相似文献
Catherine E. StewartEmail: |