Comparative genomics of the eukaryotes

A comparative analysis of the genomes of Drosophila melanogaster, Caenorhabditis elegans, and Saccharomyces cerevisiae-and the proteins they are predicted to encode-was undertaken in the context of cellular, developmental, and evolutionary processes. The nonredundant protein sets of flies and worms are similar in size and are only twice that of yeast, but different gene families are expanded in each genome, and the multidomain proteins and signaling pathways of the fly and worm are far more complex than those of yeast. The fly has orthologs to 177 of the 289 human disease genes examined and provides the foundation for rapid analysis of some of the basic processes involved in human disease.

Lottery winners and accident victims: Is happiness relative?

Adaptation level theory suggests that both contrast and habituation will operate to prevent the winning of a fortune from elevating happiness as much as might be expected. Contrast with the peak experience of winning should lessen the impact of ordinary pleasures, while habituation should eventually reduce the value of new pleasures made possible by winning. Study 1 compared a sample of 22 major lottery winners with 22 controls and also with a group of 29 paralyzed accident victims who had been interviewed previously. As predicted, lottery winners were not happier than controls and took significantly less pleasure from a series of mundane events. Study 2 indicated that these effects were not due to preexisting differences between people who buy or do not buy lottery tickets or between interviews that made or did not make the lottery salient. Paraplegics also demonstrated a contrast effect, not by enhancing minor pleasures but by idealizing their past, which did not help their present happiness.

The neprilysin (NEP) family of zinc metalloendopeptidases: genomics and function

Neprilysin (NEP), a thermolysin-like zinc metalloendopeptidase, plays an important role in turning off peptide signalling events at the cell surface. It is involved in the metabolism of a number of regulatory peptides of the mammalian nervous, cardiovascular, inflammatory and immune systems. Examples include enkephalins, tachykinins, natriuretic and chemotactic peptides. NEP is an integral plasma membrane ectopeptidase of the M13 family of zinc peptidases. Other related mammalian NEP-like enzymes include the endothelin-converting enzymes (ECE-1 and ECE-2), KELL and PEX. A number of novel mammalian homologues of NEP have also recently been described. NEP family members are potential therapeutic targets, for example in cardiovascular and inflammatory disorders, and potent and selective inhibitors such as phosphoramidon have contributed to understanding enzyme function. Inhibitor design should be facilitated by the recent three-dimensional structural solution of the NEP-phosphoramidon complex. For several of the family members, however, a well-defined physiological function or substrate is lacking. Knowledge of the complete genomes of Caenorhabditis elegans and Drosophila melanogaster allows the full complement of NEP-like activities to be analysed in a single organism. These model organisms also provide convenient systems for examining cell-specific expression, developmental and functional roles of this peptidase family, and reveal the power of functional genomics.

Lottery winners and accident victims: is happiness relative?

Adaptation level theory suggests that both contrast and habituation will operate to prevent the winning of a fortune from elevating happiness as much as might be expected. Contrast with the peak experience of winning should lessen the impact of ordinary pleasures, while habituation should eventually reduce the value of new pleasures made possible by winning. Study 1 compared a sample of 22 major lottery winners with 22 controls and also with a group of 29 paralyzed accident victims who had been interviewed previously. As predicted, lottery winners were not happier than controls and took significantly less pleasure from a series of mundane events. Study 2 indicated that these effects were not due to preexisting differences between people who buy or do not buy lottery tickets or between interviews that made or did not make the lottery salient. Paraplegics also demonstrated a contrast effect, not by enhancing minor pleasures but by idealizing their past, which did not help their present happiness.

The code within the codons

For the first time it is shown that each of the three codon bases has a general correlation with a different, predictable amino acid property, depending on position within the codon. In addition to the previously recognized link between the mid-base and the hydrophobic-hydrophilic spectrum, we show that, with the exception of G, the first base is generally invariant within a synthetic pathway. G--coded amino acids show a different order, being found only at the head of the synthetic pathways. The redundancy of the nature of the third base has a previously unrecognised relationship with molecular weight. The bases U and A (transversions) are associated with the most sharply defined or opposite states in both the first and second position, C somewhat less so or intermediate, anf G neutral. The apparently systematic nature of these relationships has profound implications for the origin of the genetic code. It appears to be the remains of the first language of the cell, predating the tRNA/ribosome system, persisting with remarkably little change at a deeper level of organisation than the codon language.

Expression and functional characterization of a Drosophila neuropeptide precursor with homology to mammalian preprotachykinin A

Peptides structurally related to mammalian tachykinins have recently been isolated from the brain and intestine of several insect species, where they are believed to function as both neuromodulators and hormones. Further evidence for the signaling role of insect tachykinin-related peptides was provided by the cloning and characterization of cDNAs for two tachykinin receptors from Drosophila melanogaster. However, no endogenous ligand has been isolated for the Drosophila tachykinin receptors to date. Analysis of the Drosophila genome allowed us to identify a putative tachykinin-related peptide prohormone (prepro-DTK) gene. A 1.5-kilobase pair cDNA amplified from a Drosophila head cDNA library contained an 870-base pair open reading frame, which encodes five novel Drosophila tachykinin-related peptides (called DTK peptides) with conserved C-terminal FXGXR-amide motifs common to other insect tachykinin-related peptides. The tachykinin-related peptide prohormone gene (Dtk) is both expressed and post-translationally processed in larval and adult midgut endocrine cells and in the central nervous system, with midgut expression starting at stage 17 of embryogenesis. The predicted Drosophila tachykinin peptides have potent stimulatory effects on the contractions of insect gut. These data provide additional evidence for the conservation of both the structure and function of the tachykinin peptides in the brain and gut during the course of evolution.

Cloning and expression of an evolutionary conserved single-domain angiotensin converting enzyme from Drosophila melanogaster

Mammalian somatic angiotensin converting enzyme (EC 3.4.15.1, ACE) consists of two highly homologous (N- and C-) domains encoded by a duplicated gene. We have identified an apparent single-domain (67 kDa) insect angiotensin converting enzyme (AnCE) in embryos of Drosophila melanogaster which converts angiotensin I to angiotensin II (Km, 365 microM), removes Phe-Arg from the C terminus of bradykinin (Km, 22 microM), and is inhibited by ACE inhibitors, captopril (IC50 = 1.1 x 10(-9) M) and trandolaprilat (IC50 = 1.6 x 10(-8) M). We also report the cloning and expression of a Drosophila AnCE cDNA which codes for a single-domain 615-amino acid protein with a predicted 17-amino acid signal peptide and regions with high levels of homology to both the N- and C-domains of mammalian somatic ACE, especially around the active site consensus sequence. Northern analysis identified a single 2.1-kilobase mRNA in Drosophila embryos, and Southern analysis of Drosophila genomic DNA indicates that the insect gene is not duplicated. When expressed in COS-7 cells, the AnCE protein is a secreted enzyme, which converts angiotensin I to angiotensin II and is inhibited by captopril (IC50 = 5.6 x 10(-9) M) and trandolaprilat (IC50 = 2 x 10(-8) M). The evolutionary significance of these results is discussed.

Blood-free selective medium for isolation of Campylobacter jejuni from feces

A blood-free selective agar is described which contains charcoal, ferrous sulfate, sodium pyruvate, casein hydrolysates, cefazolin, and sodium deoxycholate (CCD agar). CCD agar was compared with Preston medium for isolation of Campylobacter jejuni from human feces, and isolation rates were similar on both media, but CCD agar was less selective. Temperature studies at 37 and 42 degrees C confirmed that incubation of direct plates at 42 degrees C for 48 h was necessary for maximum isolation of C. jejuni.

Improved detection of Sugarcane yellow leaf virus using a real-time fluorescent (TaqMan) RT-PCR assay

Yellow leaf syndrome (YLS) of sugarcane has been associated with Sugarcane yellow leaf virus (ScYLV) and has been reported from most sugarcane growing countries around the world. As sugarcane is vegetatively propagated, it is important to use effective and sensitive detection methods to screen new propagating material. Virus detection in symptomatic tissue is currently achieved using enzyme linked immunosorbent assay (ELISA), tissue blot immunoassay (TBIA) or a conventional RT-PCR based assay. This paper reports the development of an improved assay based on multiplex real-time fluorescent RT-PCR. The new assay is 100-fold more sensitive than conventional RT-PCR, and incorporates a novel 'RNA specific' internal positive control (based around the intron of the caffeic acid 3-o-methyltransferase gene) to guard against false negative results. The paper also describes the comparison of eight RNA extraction methods for sugarcane tissue giving a number of alternatives for different laboratory situations. The sensitivity of this assay has allowed the detection of ScYLV in many samples that were thought to be healthy following conventional testing (RT-PCR, ELISA or TBIA). The detection of ScYLV using this TaqMan assay can be applied to the production of ScYLV-free plants and prevents its spread through the propagation material.

A study of thermophilic campylobacters in a river system

Fifteen kilometres of a river system traversing rural and urban areas and subject to sewage works effluent discharge was studied during a 12 1/2 month period. A total of 312 samples was collected from 12 sites at 14 d intervals and tested by a glass microfibre filtration method and a most probable number (MPN) method. Campylobacters were found in 43% of samples by the filtration method and 21% by the MPN method. The lowest frequency of isolation and lowest counts (less than 10 campylobacters/100 ml) were associated with samples collected from rural sites and fast-flowing stretches of river. The greatest frequency of isolation and highest counts (greater than 10-230 campylobacters/100 ml) were associated with sites adjacent to or downstream of sewage works. There was an obvious seasonal trend; most isolations and highest counts were obtained in late autumn and winter, and fewest isolations and lowest counts in spring and summer. Surface water run-off from adjacent farmland following heavy rainfall also increased the counts of campylobacters in the river system. Biotyping of isolates demonstrated that the most prevalent Campylobacter sp. was Campylobacter jejuni but C. coli, C. laridis and a previously unrecognized group of campylobacters were also isolated. Serotyping differentiated 14 serotypes of C. jejuni, 11 of C. coli and two of C. laridis. Furthermore, serotypes of C. jejuni commonly isolated from enteritis in man were frequently found in river water tested during this study.

Development of a blood-free Campylobacter medium: screening tests on basal media and supplements, and the ability of selected supplements to facilitate aerotolerance

The capacity of six basal media to support the growth of thermophilic campylobacters was tested. The most successful was Nutrient Broth No. 2 (Oxoid) solidified with New Zealand agar but it gave at best only a 9% recovery rate. Various blood products, iron compounds, detoxifying agents, reducing agents, growth stimulants and an antimetabolite were added to the selected basal medium and counts of inoculated organisms were compared with counts on basal medium containing 5% lysed horse blood. Of 22 supplements tried only blood, Fildes' peptic digest of blood, heamatin, iron salts, charcoal, sodium metabisulphite and sodium pyruvate greatly improved the basal medium. The ability of these supplements used singly and in combinations to facilitate aerotolerance of campylobacters was investigated. Two aspects of aerotolerance were tested; (a) the ability of the supplements to sustain the viability of campylobacters seeded onto culture plates left on the bench for up to 6 h before microaerobic incubation; and (b) the ability of the supplements to facilitate the growth of campylobacters at increasing oxygen tension (6, 10 and 17% oxygen). A combination of 0.4% charcoal, 0.025% ferrous sulphate and 0.025% sodium pyruvate was found to be as effective as blood in both tests.

The Drosophila melanogaster-related angiotensin-I-converting enzymes Acer and Ance--distinct enzymic characteristics and alternative expression during pupal development

Drosophila melanogaster express two distinct angiotensin-I-converting enzymes (ACEs) called Ance and Acer, which display a high level of primary structure similarity. We have expressed Acer in the yeast Pichia pastoris and purified the recombinant enzyme with a view to developing biochemical tools to distinguish between Acer and Ance. Purified Acer and Ance expressed in yeast were used to raise anti-Acer Ig and anti-Ance Ig that specifically cross-reacted with the respective enzyme on immunoblotting, but did not act as specific inhibitors. Acer cleaves the C-terminal dipeptides from benzoylglycyl-histidyl-leucine and [Leu5]enkephalin, and Acer and Ance are both able to act as endopeptidases, releasing the C-terminal dipeptideamide from [Leu5]enkephalinamide. However, Acer hydrolyses this substrate at a slightly faster rate than [Leu5]enkephalin, whereas Ance hydrolyses the peptide with a free C-terminus with a kcat 15-fold higher than [Leu5]enkephalinamide. In addition, Acer did not cleave angiotensin I. In contrast, Ance hydrolysed 25% of this substrate at an 8-fold lower enzyme concentration. Furthermore, Acer did not hydrolyse the synthetic substrates Phe-Ser-Pro-Arg-Leu-Gly-Arg-Arg and Phe-Ser-Pro-Arg-Leu-Gly-Lys-Arg, two partially processed putative locustamyotropin precursors, under conditions where Ance produced 82% substrate hydrolysis. Acer was inhibited by captopril, trandolaprilat and enalaprilat, with apparent Ki values in the nanomolar range, whereas lisinopril and fosinoprilat were less potent. We show that the two Drosophila ACEs are alternatively expressed in stages P1 (white puparium)-P15 (eclosion) of pupal development; Ance is expressed predominantly during stages P4-P7, whereas the ACE activity expressed during stages P9-P12 is mainly due to Acer suggesting different roles for the two enzymes during pupal development.

Functional conservation of the active sites of human and Drosophila angiotensin I-converting enzyme

Human somatic angiotensin I-converting enzyme (sACE) has two active sites present in two homologous protein domains, resulting from a tandem gene duplication. It has been proposed that the N- and C-terminal active sites can have specific in vivo roles. In Drosophila melanogaster, Ance and Acercode for two ACE-like single-domain proteins, also predicted to have distinct physiological roles. We have investigated the relationship of Ance and Acer to the N- and C-domains of human sACE by genomic sequence analysis and by using domain-selective inhibitors, including RXP 407, a selective inhibitor of the human N-domain. These phosphinic peptides were potent inhibitors of Acer, but not of Ance. We conclude that the active sites of the N-domain and of Acer share structural features that permit the binding of the unusual RXP407 inhibitor and the hydrolysis of a broader range of peptide structures. In comparison, Ance, like the human C-domain of ACE, displays greater inhibitor selectivity. From the analysis of the published sequence of the Adh region of Drosophila chromosome 2, which carries Ance, Acer, and four additional ACE-like genes, we also suggest that this functional conservation is reflected in an ancestral gene structure identifiable in both protostome and deuterostome lineages and that the duplication seen in vertebrate genomes predates the divergence of these lineages. The conservation of ACE enzymes with distinct active sites in the evolution of both vertebrate and invertebrate species provides further evidence that these two kinds of active sites have different physiological functions.

Comparison of selective media for isolation of Campylobacter jejuni/coli

A comparison of Skirrow's, Butzler's, Blaser's, Campy-BAP and Preston media for Campylobacter spp was made using human, animal and environmental specimens. Butzler's medium gave the lowest isolation rate and Preston medium, which was the most selective, the highest isolation rate. Enrichment culture using Preston enrichment broth gave a higher isolation rate than direct plating onto Preston medium.

Dose requirements of propofol by infusion during nitrous oxide anaesthesia in man. II: Patients premedicated with lorazepam

The infusion rate of propofol required to supplement 67% nitrous oxide in oxygen to maintain surgical anaesthesia was determined in 72 patients premedicated with lorazepam. Following an induction dose of propofol 2 mg kg-1, groups of eight patients received an infusion of propofol varying from 60 to 200 micrograms kg-1 min-1. Probit analysis was used to determine the ED50 (130 micrograms kg-1 min-1; 95% confidence limits: 106-167 micrograms kg-1 min-1) and ED95 (348 micrograms kg-1 min-1; 95% confidence limits: 233-1296 micrograms kg-1 min-1) for propofol infusion. Whole blood propofol concentrations at the time of surgical incision correlated strongly with the infusion rate, giving an EC50 value of 2.5 micrograms ml-1, and an EC95 value of 5.92 micrograms ml-1. There was no significant correlation between the rate of infusion of propofol, or the total propofol dose, and the times to response to command, or to recall of birthdate.

The ability of campylobacter media supplements to neutralize photochemically induced toxicity and hydrogen peroxide

Nutrient agar plates stored in light and air for 48 h became inhibitory for Campylobacter jejuni, C. coli and nalidixic acid-resistant, thermophilic campylobacter (NARTC) strains. All five campylobacter test strains showed greater than 5 log reduction in counts on media which had been stored in light and air. Media stored in the dark and/or in a reduced atmosphere did not become inhibitory and supported the growth of campylobacters. Ferrous sulphate, sodium pyruvate, blood, charcoal or sodium metabisulphite, compounds frequently used as supplements in campylobacter media, were added to nutrient agar prior to storage of media in light and air. All additives except sodium metabisulphite prevented the accumulation of photochemically generated toxic oxygen derivatives and allowed growth of test strains. In qualitative tests to determine the ability of supplements to neutralize hydrogen peroxide, blood was the most active, charcoal and sodium pyruvate slightly less active and ferrous sulphate and sodium metabisulphite the least active. The results of this study confirm that supplements in campylobacter media act as quenching or detoxifying agents and not as enrichment factors.

A most probable number method for estimating small numbers of campylobacters in water

A most probable number (MPN) method capable of estimating as few as ten campylobacters per 100 ml of water is described. The method gave results close to those obtained by the viable count method of Miles, Misra & Irwin (1938) with graded suspensions of Campylobacter jejuni. The method was used to test raw water samples: counts were obtained ranging from 10 to 230 campylobacters per 100 ml for 11 49 coastal and estuary water samples, and from 10 to 36 campylobacters per 100 ml for 7 of 44 river samples. Campylobacters were isolated from an additional 24 of the 'negative' samples by testing 200 ml volumes by glass microfibre filtration and enrichment culture methods. The MPN method should prove to be a useful epidemiological tool particularly suited to the enumeration of campylobacters in particulate fluids.

Purification and characterization of prostaglandin-H E-isomerase, a sigma-class glutathione S-transferase, from Ascaridia galli

Comparison of partial primary sequences of sigma-class glutathione S-transferases (GSH) of parasitic helminths and a GSH-dependent prostaglandin (PG)-H D-isomerase of rat immune accessory cells suggested that some of the helminth enzymes may also be involved in PG biosynthesis [Meyer and Thomas (1995) Biochem. J. 311, 739-742]. A soluble GSH transferase of the parasitic nematode Ascaridia galli has now been purified which shows high activity and specificity in the GSH-dependent isomerization of PGH to PGE, comparable to that of the rat spleen enzyme in its isomerization of PGH to PGD, and similarly stimulates the activity of prostaglandin H synthase. The enzyme subunit is structurally related to the rat spleen enzyme and sigma-class GSH transferases of helminths according to the partial primary sequence. The data support the hypothesis that some sigma-class GSH transferases of helminth parasites are involved in PG biosynthesis which, in the case of PGE, is likely to be associated with the subversion or suppression of host immunity. A PG-H E-isomerase of comparable specificity and activity has not previously been isolated.

A novel peptide-processing activity of insect peptidyl-dipeptidase A (angiotensin I-converting enzyme): the hydrolysis of lysyl-arginine and arginyl-arginine from the C-terminus of an insect prohormone peptide

Insect peptidyl-dipeptidase A [angiotensin I-converting enzyme (ACE)] is a soluble single-domain peptidyl-dipeptidase that has many properties in common with the C-domain of mammalian somatic ACE and with the single-domain mammalian germinal ACE. Mammalian somatic ACE is important in blood homoeostasis, but the role of ACE in insects is not known. Immunocytochemistry has been used to localize ACE in the neuroendocrine system of the locust, Locusta migratoria. Staining was observed in five groups of neurosecretory cells in the brain and suboesophageal ganglion, in the nervi corpori cardiaci, the storage part of the corpora cardiaca and in the nervi corpori allati. In three groups of neurosecretory cells, ACE co-localized with locustamyotropins, suggesting a possible role for the enzyme in the metabolism of these neuropeptides. We demonstrate in vitro a novel activity of ACE that removes pairs of basic amino acid residues from a locustamyotropin peptide extended at the C-terminus with either Gly-Lys-Arg or Gly-Arg-Arg, corresponding to a consensus recognition sequence for endoproteolysis of prohormone proteins by prohormone convertases. The low Km and high kcat values (Km 7.3 and 5.0 microM, kcat 226 and 207 s-1 for the hydrolysis of Phe-Ser-Pro-Arg-Leu-Gly-Lys-Arg and Phe-Ser-Pro-Arg-Leu-Gly-Arg-Arg, respectively) obtained for the hydrolysis of these two peptides by insect ACE means that these peptides, along with mammalian bradykinin, are the most favoured in vitro ACE substrates so far identified. The discovery of this in vitro prohormone-processing activity of insect ACE provides a possible explanation for the intracellular co-localization of the enzyme with locustamyotropin peptides, and provides evidence for a new role for ACE in the biosynthesis of peptide hormones and transmitters.

The Acer gene of Drosophila codes for an angiotensin-converting enzyme homologue

Mammalian angiotensin-converting enzyme (ACE) exists as two forms, somatic (sACE), controlling blood pressure via angiotensin II, and testicular (tACE), whose function is unknown. The former has two highly homologous N- and C-terminal Zn2+ metallopeptidase active sites, whereas the latter only has one, which is identical to the C-terminal domain of sACE. We have sequenced 2452 bases of a 3.1-kb mRNA whose predicted translation product shows 40% identity with mammalian testicular ACE, and 48% identity with an already identified Drosophila homologue of ACE (Ance). We have termed this gene Acer (Angiotensin converting enzyme-related). Acer mRNA is found in the developing dorsal vessel (heart) during embryogenesis. Phylogenetic analysis indicates that duplication of an ancestral ACE gene occurred in the lineage leading to the arthropods, independently of the duplication which gave rise to the two domain somatic ACE of mammals.

Insect angiotensin-converting enzyme. A processing enzyme with broad substrate specificity and a role in reproduction

Insect angiotensin-converting enzyme (ACE) is a peptidyl dipeptidase that removes dipeptides and dipeptideamides from the C-terminus of a broad range of in vitro oligopeptide substrates. In mammals, ACE has important roles in blood homeostasis and a recently recognized, but as yet undefined, role in the fertility of male mice. High levels of ACE are found in the male reproductive tissues of several insect species, and emerging data indicates an important role for the enzyme in insect reproduction. In this paper we review some of the recent findings about insect ACE, and we speculate as to the physiological role of this enzyme in insect reproduction.

FUNGAL POPULATION AND COMMUNITY DEVELOPMENT IN CUT BEECH LOGS: I. ESTABLISHMENT VIA THE AERIAL CUT SURFACE

More than 450 beech (Fagus sylvatica L.) logs, 10 to 20 cm in diameter and 30 to 40 cm long, were cut from freshly felled trees and placed upright 1 m apart with their bases buried up to 10 cm deep in the ground in a plot of about 600 m² in a mixed deciduous woodland in the Forest of Dean, Gloucestershire, UK. Fungal colonization via the aerial and buried cut surfaces was studied - in some cases following inoculation of basidiospores - using a combination of direct and indirect techniques. A wide variety of ascomycetes, basidiomycetes and fungi imperfecti were identified, by direct observation or following direct incubation of wood samples, from the vicinity of the aerial cut surface within the first six months after cutting. Some such as Coriolus versicolor (L. ex Fr.) Quél. subsequently increased in occurrence, whereas others, including Chondrostereum purpureum (Fr.) Pouz. declined. Isolation onto malt agar from thin sections of wood revealed the presence of some fungi, notably a Fusarium sp., not detected by direct means. In addition, homokaryons of the basidiomycetes Bjerkandera adusta (Willd, ex Fr.) Karst. and C. versicolor were isolated from near the aerial cut surface up to two years after cutting, and, lower down, mostly up until six months after cutting (thereafter heterokaryons predominated). Moreover, evidence was obtained that small volumes of discoloured, but not strongly decayed wood, sometimes contained large numbers of mutually antagonistic individuals (up to 30 per cm³ ) of the decay species B. adusta, C. versicolor and Stereum hirsutum (Willd. ex Fr.) S. F. Gray. Vertical penetration from the aerial cut surface showed a marked lag phase, such that for the first six weeks after cutting, overt colonization was restricted to about 3 mm depth. Thereafter the depth occupied increased rapidly.

FUNGAL POPULATION AND COMMUNITY DEVELOPMENT IN CUT BEECH LOGS: III. SPATIAL DYNAMICS, INTERACTIONS AND STRATEGIES

The spatial development, in beech logs exposed to air-borne and soil-borne inoculum, of mature fungal communities containing mutually or unilaterally exclusive mycelia of decay species is described and related to the ecological strategies and interaction of participant individuals. A combative heirarchy is recognized between (i) ruderal and/or stress-tolerant individuals which are spatially dominant early on and then decline, through (ii) air-borne combative individuals of decay fungi, such as Coriolus versicolor (L. ex Fr.) Quél. and Stereum hirsutum (Willd. ex Fr.) S. F. Gray, which establish mutually exclusive decay columns expanding away from the aerial cut surface, and culminating with (iii) highly combative individuals of mycelial cord-formers such as Phallus impudicus (L.) Pers. and Phanerochaete velutina (DC ex Pers.) Parmasto, which invade slowly from the base, ultimately occuping large volumes of wood, causing intense decay, and replacing many of the pioneers. Addition of basidiospore suspensions of Bjerkandera adusta (Willd. ex Fr.) Karst., C, versicolor, Hypholoma fasciculare (Huds. ex Fr.) Kummer or S. hirsutum to the aerial cut surface appeared to affect community dynamics and functioning markedly. Development of decay columns by air-borne fungi was inhibited and associated with enhanced vertical penetration by basally-colonizing fungi, and persistence of the relatively non-combative species Xylaria hypoxylon (L. ex Hooker) Greville and Armillaria bulbosa. (Barla) Kile & Watling. Re-cutting of the aerial cut surface resulted in community development patterns somewhat intermediate between those in naturally colonized and inoculated logs.

A study of the oxygen and carbon dioxide requirements of thermophilic campylobacters

The oxygen and carbon dioxide requirements of different biotypes of thermophilic campylobacters were investigated by means of (a) quantitative studies, and (b) total growth studies. Oxygen tolerance of the five test organisms differed markedly and varied with the carbon dioxide concentration. At most carbon dioxide concentrations tested, Campylobacter jejuni strains NCTC 11168 and NCTC 11392 tolerated 21% oxygen (growth reduced), C coli NCTC 11353 tolerated 15% oxygen (growth reduced), and C jejuni ATCC 3036 and (nalidixic acid resistant thermophilic campylobacter) NCTC 11352 tolerated 10% oxygen (growth not reduced). Total growth studies indicated that 10% oxygen was the optimal concentration for growth of the five test organisms. All exhibited a requirement for carbon dioxide, and only C jejuni strains NCTC 11168 and NCTC 11392 tolerated its absence (growth reduced), when the oxygen concentration was low. The studies indicated that atmospheres containing 5% to 10% oxygen and 1.0% to 10% carbon dioxide are suitable for growth of the various biotypes of thermophilic campylobacters. The oxygen and carbon dioxide concentrations produced in anaerobic jars by variations of the evacuation-replacement technique were determined and suitable practices identified.

Improved detection of barley yellow dwarf virus in single aphids using RT-PCR

The detection of a British isolate of barley yellow dwarf virus (BYDV-G, PAV-like) from individual vector aphids, using a combined assay of reverse transcription and polymerase chain reaction (RT-PCR) is reported. The method makes use of a multiplex format, including internal control primers directed at conserved regions of insect actin. The actin primers serve as controls for each stage of the method and are suitable for use in a range of invertebrate species. Detection of BYDV in vector aphids for use in forecasting systems is at present carried out using an enzyme-amplified ELISA system. In direct comparisons with the amplified ELISA, RT-PCR shows an increase in sensitivity detecting 11 fg of purified virus. Detection of virus in ELISA-negative aphids by RT-PCR was also demonstrated, and its potential as a routine diagnostic tool for virus detection in aphids is discussed.