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1.
2.
Plant chloroplasts are not only the main cellular location for storage of elemental iron (Fe), but also the main site for Fe, which is incorporated into chlorophyll, haem and the photosynthetic machinery. How plants measure internal Fe levels is unknown. We describe here a new Fe‐dependent response, a change in the period of the circadian clock. In Arabidopsis, the period lengthens when Fe becomes limiting, and gradually shortens as external Fe levels increase. Etiolated seedlings or light‐grown plants treated with plastid translation inhibitors do not respond to changes in Fe supply, pointing to developed chloroplasts as central hubs for circadian Fe sensing. Phytochrome‐deficient mutants maintain a short period even under Fe deficiency, stressing the role of early light signalling in coupling the clock to Fe responses. Further mutant and pharmacological analyses suggest that known players in plastid‐to‐nucleus signalling do not directly participate in Fe sensing. We propose that the sensor governing circadian Fe responses defines a new retrograde pathway that involves a plastid‐encoded protein that depends on phytochromes and the functional state of chloroplasts. 相似文献
3.
Cellulolytic bacteria became established 12 days after birth in the caecum and colon of conventionally-reared mice fed a diet containing 5 p. 100 crude cellulose (Weende). Their population reached a level between 10(6) and 10(7) bacteria per gram of digestive contents in 25-day-old animals. However, variations between animals were very large; 20 to 50% of the individuals were free of cellulolytic bacteria. A low cellulolytic population was observed in adult mice fed a cellulose-free diet. The amount of cellulose in the diet and its nature (crude or pure cellulose) affected the number of cellulolytic bacteria: the higher the percentage of cellulose in the diet, the higher the number of cellulolytic bacteria, in particular with crude cellulose-containing diet. 相似文献
4.
Abstract. The pupal stage of ten Coelometopini species occurring in Australia, New Guinea, Southeast Asia and the Pacific region are described and a key for their identification is provided. The species are Chrysopeplus expolitus Broun, Derosphaerus hirtipes Kaszab, Hypaulax crenata (Boisduval), Leprocaulus borneensis Kaszab, Metisopus purpureipennis Bates, Promethis carteri Kaszab, P. nigra (Blessig), P. quadraticollis (Gebien), P. quadricollis Pascoe and P. sulcigera (Boisduval). The gin trap structures of D. hirtipes and P. quadraticollis are described in detail using scanning electron micrographs. A summary of antipredator structures of all known Coelometopini pupae is given. The phylogenetic value of pupal characters is assessed at intra‐ and intergeneric levels within the tribe. 相似文献
5.
Intestinal microflora of the newborn rat as related to mammary, faecal, and vaginal Staphylococci strains isolated from the dam 总被引:2,自引:0,他引:2
To determine the relative importance of maternal microflora (faeces, vagina, and teats) in the contamination of newborn rats, strains of staphylococci from six different families (dam + litter) were isolated. These strains were identified, and by means of numerical profiles analyzed for their degree of similarity for each litter and (or) biotope. The staphylococci strains found in the gut of the newborn rat originated first from the teats and thereafter from the faeces. Concomitant observation of some identical strains, however, suggested a certain degree of similarity between these two maternal biotopes in this animal. 相似文献
6.
Establishment of ciliate protozoa in the rumen of conventional and conventionalized lambs: influence of diet and management conditions 总被引:1,自引:0,他引:1
The establishment of ciliate protozoa in the rumen was studied in conventional lambs reared under different conditions of management. The role of the microflora in the kinetics of this establishment was also investigated in conventionalized lambs. In lambs reared under farm conditions ciliate protozoa appeared in the following order: Entodinium (15-20 days), Polyplastron, Eudiplodinium, and Epidinium (20-25 days), and Isotricha (50 days). Entodinium was the most abundant (10(5)-10(6) ciliates mL-1). During the 3rd month, ciliates disappeared spontaneously in about 60% of the lambs during a period that varied from 1 to 4 weeks. In lambs fed only cow's milk Entodinium spp. and Polyplastron multivesiculatum became established at low levels. The results obtained with the conventionalized lambs demonstrate that the establishment of the ciliates in the rumen requires that the bacterial flora be well established beforehand. 相似文献
7.
Jaime F. Angulo Jaime Schwencke Patrice L. Moreau Ethel Moustacchi Raymond Devoret 《Molecular & general genetics : MGG》1985,201(1):20-24
Summary In Saccharomyces cerevisiae, a protein was recognized by polyclonal antibodies raised against homogeneous Escherichia coli K12 RecA protein. The cellular level of the yeast protein called RecAsc (molecular weight 44 kDa, pI 6.3), was transiently enhanced after UV irradiation. Protease inhibitors were required to minimize degradation of the RecAsc protein during cell lysis. The RecAsc protein exhibited similar basal levels and similar kinetics of increase after UV irradiation in DNA-repair proficient (RAD
+) strains carrying mitochondrial DNA or not (rho
0). This was also true for the following DNA-repair deficient (rad
-) strains: rad2-6 rad6-1 rad52-1, a triple mutant blocked in three major repair pathways; rad6-, a mutant containing an integrative deletion in a gene playing a central role in mutagenesis; pso2-1, a mutant that exhibits a reduced rate of mutagenesis and recombination after exposure to DNA cross-linking agents. 相似文献
8.
T Patrice B Dreno J Weber L Le Bodic H Barriere 《Plastic and reconstructive surgery》1985,76(4):554-557
The argon laser, which has been proven both useful and safe for port-wine stain therapy, interacts with the hemoglobin of the vessels. In a percentage of cases, this treatment is still inefficient, and there is a lack of correlation between these bad results and clinical or histologic criteria. Thermography, which explores the vascularization of the port-wine stain, leads us to consider port-wine stains from a physical point of view. This very simple test shows no correlation with the clinical parameters of port-wine stain but is closely related to the results obtained with laser therapy. It seems to be a good criterion to estimate the argon laser treatment prognosis. 相似文献
9.
Optimum growth conditions for the fermentation of non-concentrated whey permeate by Kluyveromyces fragilis NRRL 665 have been defined. Use of 3.75 g yeast extract l?1, a growth temperature of 38°C and a pH of 4.0 allowed a maximum productivity of 5.23 g ethanol l?1 h?1 in continuous culture with a yield 91% of theoretical. Complete batch fermentation of permeate with 100 g lactose l?1 was possible with a maximum specific growth rate of 0.276 h?1 without any change in ethanol yield. Fermentation of concentrated permeate resulted, however, in a general decrease of specific substrate consumption rate, demonstrated by the inability to completely convert an initial 90 or 150 g lactose l?1 in continuous culture, even at dilution rates as low as 0.05 and 0.08 h?1, respectively. The decrease could be related to substrate inhibition, to an increase in osmotic pressure caused by lactose and salts, and to ethanol inhibition of both alcohol and biomass yield. The decrease in specific productivity could be counterbalanced by use of high cell density cultures, obtained by cell recycle of K. fragilis. Fermentation of a non-concentrated permeáte at a dilution rate of 1 h?1 resulted in a productivity of 22 g l?1 h?1 at 22 g ethanol l?1. Cell recycle using flocculating Kluyveromyces lactis NCYC 571 was also tested. With this strain a productivity of 9.3 g l?1 h?1 at 45 g product l?1 was attained at a dilution rate of 0.2 h?1, with an initial lactose concentration of 95 g l?1. 相似文献
10.
Ecological factors determining establishment of cellulolytic bacteria and protozoa in the rumens of meroxenic lambs 总被引:2,自引:0,他引:2
Ecological factors that control the establishment of cellulolytic bacteria and ciliate protozoa in the lamb rumen were studied in meroxenic animals. Axenic lambs received dilutions of rumen liquor from either conventional lambs and sheep (pool A) or meroxenic lambs (pool B). The total number of bacteria established in the rumen was between 10(9) and 5 x 10(10) g-1. In lambs inoculated with dilutions (10(-6), 10(-7), 10(-8)) of pool A, cellulolytic bacteria did not become established. However, subsequent inoculation with Bacteroides succinogenes, resulted in colonization in lambs that had received 10(-6) and 10(-7) dilutions of pool A. However, B. succinogenes became established in only one of three lambs that received the 10(-8) dilution. Similar results were obtained for the protozoan Entodinium sp. With pool B, lambs were inoculated earlier and cellulolytic bacteria were established directly from the 10(-6) and 10(-7) inocula. Polyplastron multivesiculatum establishment occurred readily when inoculated into the lambs which had received the 10(-6) dilution of pool B. Results obtained in this study suggest that establishment of cellulolytic bacteria and protozoa requires an abundant and complex flora and is favoured by early animal inoculation. 相似文献