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1.
Studying Pneumocystis has proven to be a challenge from the perspective of propagating a significant amount of the pathogen in a facile manner.
The study of several fungal pathogens has been aided by the use of invertebrate model hosts. Our efforts to infect the invertebrate
larvae Galleria
mellonella with Pneumocystis proved futile since P. murina neither caused disease nor was able to proliferate within G. mellonella. It did, however, show that the pathogen could be rapidly cleared from the host. 相似文献
2.
Recently, the prenyltransferase SirD was found to be responsible for the O-prenylation of tyrosine in the biosynthesis of sirodesmin PL in Leptosphaeria maculans. In this study, the behavior of SirD towards phenylalanine/tyrosine and tryptophan derivatives was investigated. Product
formation has been observed with 12 of 19 phenylalanine/tyrosine derivatives. It was shown that the alanine structure attached
to the benzene ring and an electron donor, e.g., OH or NH2, at its para-position are essential for the enzyme activity. Modifications were possible both at the side chain and the benzene ring.
Enzyme products from seven phenylalanine/tyrosine derivatives were isolated and characterized by MS and NMR analyses including
HSQC and HMBC and proven to be O- or N-prenylated derivatives at position C4 of the benzene rings. K
M
values of six selected derivatives were found in the range of 0.10–0.68 mM. Catalytic efficiencies (K
cat/K
M
) were determined in the range of 430–1,110 s−1·M−1 with l-tyrosine as the best substrate. In addition, 7 of 14 tested tryptophan analogs were also accepted by SirD and converted to
C7-prenylated derivatives, which was confirmed by comparison with products obtained from enzyme assays using a 7-dimethylallyltryptophan
synthase 7-DMATS from Aspergillus fumigatus. 相似文献
3.
4.
We have investigated the floral ontogeny of Arillastrum, Allosyncarpia, Stockwellia and Eucalyptopsis (of the eucalypt group, Myrtaceae) using scanning electron microscopy and light microscopy. Several critical characters for establishing relationships between these genera and to the eucalypts have been determined. The absence of compound petaline primordia in Arillastrum, Allosyncarpia, Stockwellia and Eucalyptopsis excludes these taxa from the eucalypt clade. Post-anthesis circumscissile abscission of the hypanthium above the ovary in Stockwellia, Eucalyptopsis and Allosyncarpia is evidence that these three taxa form a monophyletic group; undifferentiated perianth parts and elongated fusiform buds are characters that unite Stockwellia and Eucalyptopsis as sister taxa. No floral characters clearly associate Arillastrum with either the eucalypt clade or the clade of Stockwellia, Eucalyptopsis and Allosyncarpia.We gratefully acknowledge Clyde Dunlop and Bob Harwood (Northern Territory Herbarium) for collecting specimens of Allosyncarpia, and Bruce Gray (Atherton) for collecting specimens of Stockwellia. The Australian National Herbarium (CANB) kindly lent herbarium specimens of Eucalyptopsis for examination. This research was supported by a University of Melbourne Research Development Grant to Andrew Drinnan. 相似文献
5.
New combinations are proposed in anticipation of the Polygonaceae treatment in the forthcoming volume of Intermountain Flora:
Polygonum kelloggii var. esotericum, P. kelloggii var. watsonii
,
Rumex densiflorus var. pycnanthus
,
R. salicifolius var. utahensis, and R. occidentalis var. tomentellus. Typifications are proposed to facilitate ongoing studies in Polygonaceae and to maintain current usage. 相似文献
6.
7.
Tropilaelaps
mercedesae is a serious ectoparasite of Apis
mellifera in China. The aim of this study was to investigate the infestation rates and intensity of T. mercedesae in A. mellifera in China, and to explore the relative importance of climate, district, management practices and beekeeper characteristics
that are assumed to be associated with the intensity of T. mercedesae. Of the 410 participating apiaries, 379 apiaries were included in analyses of seasonal infestation rates and 352 apiaries
were included in multivariable regression analysis. The highest infestation rate (86.3%) of T. mercedesae was encountered in autumn, followed by summer (66.5%), spring (17.2%) and winter (14.8%). In autumn, 28.9% (93) of the infested
apiaries were in the north (including the northeast and northwest of China), 71.1% (229) were in the central and south (including
east, southeast and southwest China), and 306 apiaries (82.9%) were co-infested by both T. mercedesae and Varroa. Multivariable regression analysis showed that geographical location, season, royal jelly collection and Varroa infestation were the factors that influence the intensity of T. mercedesae. The influence of beekeeper’s education, time of beekeeping, operation size, and hive migration on the intensity of T. mercedesa was not statistically significant. This study provided information about the establishment of the linkage of the environment
and the parasite and could lead to better timing and methods of control. 相似文献
8.
The maT clade of transposons is a group of transposable elements intermediate in sequence and predicted protein structure to mariner and Tc transposons, with a distribution thus far limited to a few invertebrate species. We present evidence, based on searches of publicly available databases, that the nematode Caenorhabditis briggsae has several maT-like transposons, which we have designated as CbmaT elements, dispersed throughout its genome. We also describe two additional transposon sequences that probably share their evolutionary history with the CbmaT transposons. One resembles a fold back variant of a CbmaT element, with long (380-bp) inverted terminal repeats (ITRs) that show a high degree (71%) of identity to CbmaT1. The other, which shares only the 26-bp ITR sequences with one of the CbmaT variants, is present in eight nearly identical copies, but does not have a transposase gene and may therefore be cross mobilised by a CbmaT transposase. Using PCR-based mobility assays, we show that CbmaT1 transposons are capable of excising from the C. briggsae genome. CbmaT1 excised approximately 500 times less frequently than Tcb1 in the reference strain AF16, but both CbmaT1 and Tcb1 excised at extremely high frequencies in the HK105 strain. The HK105 strain also exhibited a high frequency of spontaneous induction of unc-22 mutants, suggesting that it may be a mutator strain of C. briggsae. 相似文献
9.
Lima FL de Carvalho MA Apolônio AC Bemquerer MP Santoro MM Oliveira JS Alviano CS Farias Lde M 《Journal of industrial microbiology & biotechnology》2008,35(2):103-110
Aggregatibacter (Actinobacillus) actinomycetemcomitans P7–20 strain isolated from a periodontally diseased patient has produced a bacteriocin (named as actinomycetemcomitin) that is
active against Peptostreptococcus anaerobius ATCC 27337. Actinomycetemcomitin was produced during exponential and stationary growth phases, and its amount decreased until
it disappeared during the decline growth phase. It was purified by ammonium sulphate precipitation (30–60% saturation), and
further by FPLC (mono-Q ionic exchange and Phenyl Superose hydrophobic interaction) and HPLC (C-18 reversed-phase). This bacteriocin
loses its activity after incubation at a pH below 7.0 or above 8.0, following heating for 30 min at 45°C, and after treatment
with proteolytic enzymes such as trypsin, α-chymotrypsin, and papain. Actinomycetemcomitin has a molecular mass of 20.3 KDa
and it represents a new bacteriocin from A. actinomycetemcomitans. 相似文献
10.
11.
A genetic transformation system has been developed for callus cells of Crataegus
aronia using Agrobacterium
tumefaciens. Callus culture was established from internodal stem segments incubated on Murashige and Skoog (MS) medium supplemented with
5 mg l−1 Indole-3-butyric acid (IBA) and 0.5 mg l−1 6-benzyladenine (BA). In order to optimize the callus culture system with respect to callus growth and coloration, different
types and concentrations of plant growth regulators were tested. Results indicated that the best average fresh weight of red
colored callus was obtained on MS medium supplemented with 2 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.5 mg l−1 kinetin (Kin) (callus maintenance medium). Callus cells were co-cultivated with Agrobacterium harboring the binary plasmid pCAMBIA1302 carrying the mgfp5 and hygromycin phosphotransferase (hptII) genes conferring green fluorescent protein (GFP) activity and hygromycin resistance, respectively. Putative transgenic calli
were obtained 4 weeks after incubation of the co-cultivated explants onto maintenance medium supplemented with 50 mg l−1 hygromycin. Molecular analysis confirmed the integration of the transgenes in transformed callus. To our knowledge, this
is the first time to report an Agrobacterium-mediated transformation system in Crataegus
aronia. 相似文献
12.
Ferreira LQ Avelar KE Vieira JM de Paula GR Colombo AP Domingues RM Ferreira MC 《Current microbiology》2007,54(5):348-353
The Bacteroides genus, the most prevalent anaerobic bacteria of the intestinal tract, carries a plethora of the mobile elements, such as
plasmids and conjugative and mobilizable transposons, which are probably responsible for the spreading of resistance genes.
Production of β-lactamases is the most important resistance mechanism including cephalosporin resistance to β-lactam agents
in species of the Bacteroides fragilis group. In our previous study, the cfxA gene was detected in B. distasonis species, which encodes a clinically significant broad-spectrum β-lactamase responsible for widespread resistance to cefoxitin
and other β-lactams. Such gene has been associated with the mobilizable transposon Tn4555. Therefore, the aim of this study was to detect the association between the cfxA gene and the presence of transposon Tn4555 in 53 Bacteroides strains isolated in Rio de Janeiro, Brazil, by PCR assay. The cfxA gene was detected in 11 strains and the Tn4555 in 15. The transposon sequence revealed similarities of approximately 96% with the B. vulgatus sequence which has been deposited in GenBank. Hybridization assay was performed in attempt to detect the cfxA gene in the transposon. It was possible to associate the cfxA gene in 11 of 15 strains that harbored Tn4555. Among such strains, 9 presented the cfxA gene as well as Tn4555, but in 2 strains the cfxA gene was not detected by PCR assay. Our results confirm the involvement of Tn4555 in spreading the cfxA gene in Bacteroides species. 相似文献
13.
Kurtzman CP 《Antonie van Leeuwenhoek》2011,100(3):455-462
Ogataea
parapolymorpha sp. n. (NRRL YB-1982, CBS 12304, type strain), the ascosporic state of Candida
parapolymorpha, is described. The species appears homothallic, assimilates methanol as is typical of most Ogataea species and forms hat-shaped ascospores in asci that become deliquescent. O. parapolymorpha is closely related to Ogataea
angusta and Ogataea
polymorpha. The three species can be resolved from gene sequence analyses but are unresolved from fermentation and growth reactions
that are typically used for yeast identification. On the basis of multiple isolates, O. angusta is known only from California, USA, in association with Drosophila and Aulacigaster flies, O. parapolymorpha is predominantly associated with insect frass from trees in the eastern USA but O. polymorpha has been isolated from various substrates in the USA, Brazil, Spain and Costa Rica. 相似文献
14.
Karolina Vrandecic Drazenka Jurkovic Luca Riccioni Jasenka Cosic Tomislav Duvnjak 《Mycopathologia》2010,170(1):51-60
Sunflower (Helianthus annuus) stem canker caused by Diaporthe helianthi is one of the most important sunflower diseases in Croatia. Until recently, sunflower was the only known host for D. helianthi. In our research carried out in the area of Eastern Croatia, isolates of Diaporthe/Phomospis were collected from Xanthium italicum, X. strumarium and Arctium lappa. Using morphological, cultural and molecular ITS rDNA data, isolates from these weeds were identified as D. helianthi. The following isolates were used in the pathogenicity test: one isolate originated from sunflower (Su5/04), three from X. italicum (Xa2, Xa3 and Xa5), two from X. strumarium (Xa9 and Xa12), one from Xanthium sp. (Xa13) and one from A. lappa (Ar3). According to the results, it was determined that isolate Xa5 (originated from X. italicum) was the most pathogenic to sunflower stems. The average length of the lesion was 11.3 cm. The lowest level of pathogenicity
was found in Xa9 (isolated from X. strumarium). The length of the lesion was 0.1 cm. 相似文献
15.
The relationship between Sporidiobolus johnsonii and S. salmonicolor was investigated using rDNA sequence data. Two statistically well-supported clades were obtained. One clade included the
type strain of S. johnsonii and the other included the type strain of S. salmonicolor. However, some mating strains of S. salmonicolor were found in the S. johnsonii group. These strains belonged to mating type A2 and were sexually compatible with mating type A1 strains from the S. salmonicolor group. DNA–DNA reassociation values were high within each clade and moderate between the two clades. In the re-investigation
of teliospore germination, we observed that the basidia of S. salmonicolor were two-celled. In S. johnsonii, basidia were not formed and teliospore germination resulted in direct formation of yeast cells. We hypothesize that the
S. johnsonii clade is becoming genetically isolated from the S. salmonicolor group and that a speciation process is presently going on. We suspect that the observed sexual compatibility between strains
of the S. johnsonii and S. salmonicolor groups and the possible genetic flow between the two species has little biological relevance because distinct phenotypes
have been fixed in the two taxa and intermediate (hybrid) sequences for LSU and ITS rDNAs have not been detected.
An erratum to this article can be found at 相似文献
16.
Sushil Kumar Raghvendra Kumar Mishra Anil Kumar Suchi Srivastava Swati Chaudhary 《Planta》2009,230(3):449-458
Pisum sativum L., the garden pea crop plant, is serving as the unique model for genetic analyses of morphogenetic development of stipule,
the lateral organ formed on either side of the junction of leafblade petiole and stem at nodes. The stipule reduced (st) and cochleata (coch) stipule mutations and afila (af), tendril-less (tl), multifoliate-pinna (mfp) and unifoliata-tendrilled
acacia (uni-tac) leafblade mutations were variously combined and the recombinant genotypes were quantitatively phenotyped for stipule morphology
at both vegetative and reproductive nodes. The observations suggest a role of master regulator to COCH in stipule development. COCH is essential for initiation, growth and development of stipule, represses the UNI-TAC, AF, TL and MFP led leafblade-like morphogenetic pathway for compound stipule and together with ST mediates the developmental pathway for
peltate-shaped simple wild-type stipule. It is also shown that stipule is an autonomous lateral organ, like a leafblade and
secondary inflorescence. 相似文献
17.
M. E. Cocom Pech W. de J. May-Itzá L. A. Medina Medina J. J. G. Quezada-Euán 《Insectes Sociaux》2008,55(4):428-433
Euglossa viridissima is an orchid bee that forms both solitary and multiple female nests, making it a suitable species for the study of factors
leading to diverse degrees of sociality in Euglossines. We conducted observations in eight reused nests (where a first generation
of bees had been produced) kept in artificial boxes from the Yucatan Peninsula, Mexico. Five nests were reused (reactivated)
by a single female (SFN), two nests reused by a mother and one daughter (MFN1) and one nest reused by the mother and two daughters
(MFN2). No single nest was reactivated by unrelated females. The number of foraging trips, their duration and the duration
of cell provisioning was not different between SFN and MFN. The overall production of cells per female was not different either
between both types of nest. However, in MFN although all females did lay eggs, there was a reproductive skew in favor of the
mother (95 and 45% of the brood produced in MFN1 and MFN2 respectively). She showed reproductive control of her daughters
through oophagy and displaying threatening behavior when the daughters tried to open a cell where she had laid an egg. Brood
losses to parasites (Anthrax sp. (Bom-byliidae) and Hoplostelis bivittata (Megachilidae)) were only found in SFN which possibly reflects and advantage of MFN in this respect. Our results coupled
with other studies in Euglossa, reveal that a wide range of social behaviors occur in this genus, from solitary and communal to primitive reproductive division
of labor. Multiple factors involving different levels of pressure imposed by food availability and parasites may favor such
a diverse range of nesting behaviors. Interestingly, female associations in E. viridissima seem a result of kin selection that is enforced by coercion from mother females on their daughters. More studies are needed
to shed light upon the social organization of Euglossa and other Euglossines and on their phylogenetic relationships in order to trace the origins of eusociality in Apidae.
Received 12 February 2008; revised 25 June 2008; accepted 17 July 2008. 相似文献
18.
Yu-Tze Horng Kai-Chih Chang Ta-Chung Chou Chung-Jen Yu Chih-Ching Chien Yu-Hong Wei Po-Chi Soo 《Journal of industrial microbiology & biotechnology》2010,37(7):707-716
1,3-Propanediol (1,3-PD) can be used for the industrial synthesis of a variety of compounds, including polyesters, polyethers,
and polyurethanes. 1,3-PD is generated from petrochemical and microbial sources. 1,3-Propanediol is a typical product of glycerol
fermentation, while acetate, lactate, 2,3-butanediol, and ethanol also accumulate during the process. Substrate and product
inhibition limit the final concentration of 1,3-propanediol in the fermentation broth. It is impossible to increase the yield
of 1,3-propanediol by using the traditional whole-cell fermentation process. In this study, dhaD and dhaK, the genes for glycerol dehydrogenase and dihydroxyacetone kinase, respectively, were inactivated by homologous recombination
in Klebsiella pneumoniae. The dhaD/dhaK double mutant (designated TC100), selected from 5,000 single or double cross homologous recombination mutants, was confirmed
as a double cross by using polymerase chain reaction. Analysis of the cell-free supernatant with high-performance liquid chromatography
revealed elimination of lactate and 2,3-butanediol, as well as ethanol accumulation in TC100, compared with the wild-type
strain. Furthermore, 1,3-propanediol productivity was increased in the TC100 strain expressing glycerol dehydratase and 1,3-PDO
dehydrogenase regulated by the arabinose PBAD promoter. The genetic engineering and medium formulation approaches used here should aid in the separation of 1,3-propanediol
from lactate, 2,3-butanediol, and ethanol and lead to increased production of 1,3-propanediol in Klebsiella pneumoniae. 相似文献
19.
Takashi Okada Andrew S. Catanach Susan D. Johnson Ross A. Bicknell Anna M. Koltunow 《Sexual plant reproduction》2007,20(4):199-211
Asexual seed formation (apomixis) in Hieracium aurantiacum occurs by mitotic embryo sac formation without prior meiosis in ovules (apomeiosis), followed by fertilization-independent
embryo and endosperm development. Sexual reproduction begins first in Hieracium ovules with megaspore mother cell (MMC) formation. Apomixis initiates with the enlargement of somatic cells, termed aposporous
initial (AI) cells, near sexual cells. AI cells grow towards sexually programmed cells undergoing meiosis, which degrade as
the dividing nuclei of AIs obscure and displace them. Following Agrobacterium-mediated transformation of an aneuploid Hieracium aurantiacum apomict, a somaclonal mutant designated “loss of apomeiosis 1” (loa1) was recovered, which had significantly lost the ability to form apomictic seed. Maternal apomictic progeny were rare and
low levels of germinable seedlings were primarily derived from meiotically derived eggs. Cytological analysis revealed defects
in AI formation and function in loa1. Somatic cells enlarged some distance away from sexual cells and unlike AI cells, these expanded away from sexual cells without
nuclear division. Surprisingly, many accumulated callose in the walls, a marker associated with meiotically specified cells.
These defective AI (DAI) cells only had partial sexual identity as they failed to express a marker reflecting entry to meiosis
that was easily detected in MMCs and they ultimately degraded. DAI cell formation did not lead to a compensatory increase
in functional sexual embryo sacs, as collapse of meiotic embryo sacs was prevalent in the aneuploid somaclonal mutant. Positional
cues that are important for AI cell differentiation, growth and fate may have been disrupted in the loa1 mutant and this is discussed.
The authors Takashi Okada, Andrew S. Catanach and Susan D. Johnson made equal contributions to the data. 相似文献
20.
A synthetic chimeric gene SbtCryIII(A) encoding the insecticidal protein btCryIII(A), was transformed into Pinus armandii embryos and embryogenic calli using Agrobacterium tumefaciens. Polymerase chain reaction and genomic DNA Southern blot analysis showed that the SbtCryIII(A) gene was integrated into the genome of transgenic Pinus armandii plants, and Northern blot analysis indicated that the SbtCryIII(A) gene was transcribed. 相似文献