Biomedical subjects

M Slaytor

Publications and source records attributed to M Slaytor.

11 recordsLinked to original sources

PubMed2002

New endo-beta-1,4-glucanases from the parabasalian symbionts, Pseudotrichonympha grassii and Holomastigotoides mirabile of Coptotermes termites.

Abstract. An endo-beta-1,4-glucanase (EG) was purified from the hindgut of an Australian mound-building termite, Coptotermes lacteus. The hindgut extract had a peak separate from those for extracts obtained from the salivary glands and the midgut based on sephacryl S-200 gel chromatography, and also demonstrated an origin different from the endogenous EGs of the termite itself. The recovery was further purified by SDS-PAGE, and its N-terminal amino acid sequence analyzed. This showed high homology to EGs from glycoside hydrolase family (GHF) 7. PCR-based cloning methods were applied to the hindgut contents of C. lacteus and individual protozoan symbionts from C formosanus. cDNAs encoding putative EGs homologous to GHF7 members were then identified. The functionality of one of the putative proteins was confirmed by its expression in Escherichia coli.

Amino Acid Sequence↗

PubMed2000

Evidence from multiple gene sequences indicates that termites evolved from wood-feeding cockroaches.

Despite more than half a century of research, the evolutionary origin of termites remains unresolved [1] [2] [3]. A clear picture of termite ancestry is crucial for understanding how these insects evolved eusociality, particularly because they lack the haplodiploid genetic system associated with eusocial evolution in bees, ants, wasps and thrips [4] [5]. Termites, together with cockroaches and praying mantids, constitute the order Dictyoptera, which has been the focus of numerous conflicting phylogenetic studies in recent decades [6] [7] [8] [9] [10] [11] [12]. With the aim of settling the debate over the sister-group of termites, we have determined the sequences of genes encoding 18S ribosomal RNA, mitochondrial cytochrome oxidase subunit II (COII) and endogenous endo-beta-1, 4-glucanase (EG) from a diverse range of dictyopterans. Maximum parsimony and likelihood analyses of these sequences revealed strong support for a clade consisting of termites and subsocial, wood-feeding cockroaches of the genus Cryptocercus. This clade is nested within a larger cockroach clade, implicating wood-feeding cockroaches as an evolutionary intermediate between primitive non-social taxa and eusocial termites.

Animals↗

PubMed1999

Metazoan cellulase genes from termites: intron/exon structures and sites of expression.

Endogenous endo-beta-1,4-glucanase (EGase, EC 3.2.1.4) cDNAs were cloned from representatives of the termite families Termitidae and Rhinotermitidae. These EGases are all composed of 448 amino acids and belong to glycosyl hydrolase family 9 (GHF9), sharing high levels of identity (40-52%) with selected bacterial, mycetozoan and plant EGases. Like most plant EGases, they consist of a single catalytic domain, lacking the ancillary domains found in most microbial cellulases. Using a PCR-based strategy, the entire sequence of the coding region of NtEG, a gene putatively encoding an EGase from Nasutitermes takasagoensis (Termitidae), was determined. NtEG consists of 10 exons interrupted by 9 introns and contains typical eukaryotic promoter elements. Genomic fragments of EGase genes from Reticulitermes speratus (Rhinotermitidae) were also sequenced. In situ hybridization of N. takasagoensis guts with an antisense NtEG RNA probe demonstrated that expression occurs in the midgut, which contrasts to EGase expression being detected only in the salivary glands of R. speratus. NtEG, when expressed in Escherichia coli, was shown to have in vitro activity against carboxymethylcellulose.

Animals↗

PubMed1994

Functions of symbiotic fungus gardens in higher termites of the genus Macrotermes: evidence against the acquired enzyme hypothesis.

Behavioural, microbiological and biochemical studies on Macrotermes subhyalinus and M. michaelseni by collaborating laboratories in the U.K., Switzerland and Australia are described. Younger workers consume both primary forage and the conidia of a symbiotically associated fungus of the genus Termitomyces, but all workers produce a fully competent cellulase complex (endoglucanase + glucosidase) in the midgut which is clearly distinguishable from analogous enzymes in fungal tissues. Workers have a RQ of 1.0; although a bacterial flora is present, assessments of CH4/H2 efflux and intestinal VFAs suggest that respiration is sustained by aerobic carbohydrate dissimilation. Calculations based on estimates of food ingestion by workers and measurements of cellulase activity show that endogenous production of reducing sugars from polysaccharide is sufficient to sustain the observed metabolic rate. Conidia contain both cellulase and glucose at much higher concentrations than other fungal tissues, but the role and fate of these substances on entering the young worker guts is unknown. Older workers consume fully composted forage in which cellulose, hemicellulose, pectin and lignin are all significantly degraded, with a corresponding increase in nitrogen content.

Animals↗

PubMed1988

N,N-Dimethyltryptamine Production in Phalaris aquatica Seedlings: A Mathematical Model for its Synthesis.

The activities of three enzymes and the concentration of intermediates involved in the synthesis of N,N-dimethyltryptamine (DMT) from endogenous tryptophan (TRP) have been measured in vitro in seedlings of Phalaris aquatica L. cv Australian Commercial over 16 days after planting. The activities of tryptophan decarboxylase and the two N-methyl-transferases increased rapidly to maximal rates of substrate conversion at day 5 of 95, 1000, and 2200 micromoles per hour per milliliter, respectively. After these maximal rates, the activities decreased rapidly. The concentration of intermediates increased rapidly from zero in the seeds to maximal values of 25 and 53 micromolar at day 5 for tryptamine (T) and N-methyltryptamine (MT), respectively, 1000 micromolar at day 6 for TRP, and 650 micromolar at day 8 for DMT. The concentration of DMT and of all the intermediates in its synthesis declined rapidly after the maximal value had been reached. A mathematical model of the pathway from TRP to DMT using these enzymes correctly predicts the concentrations of T and MT, intermediates whose concentration is determined only by the pathway, and confirms that these three enzymes are responsible for the in vivo synthesis of DMT. Kinetic studies are reported for these enzymes. Tryptophan decarboxylase uses pyridoxal phosphate (PALP) as a coenzyme and has the following kinetic constants: K(m) (PALP) = 2.5 micromolar, K(m) (TRP) = 200 micromolar, K(i) (MT) = 5 millimolar, and K(i) (DMT) = 4 millimolar. The N-methyltransferases use S-adenosylmethionine (SAM) as substrate; S-adenosylhomocysteine (SAH) is assumed to be the product. The mechanism of secondary indolethylamine-N-methyltransferase, determined by initial velocity studies, is rapid equilibrium random with formation of both dead end complexes. Secondary indolethylamine-N-methyltransferase methylates both MT and 5-methoxy-N-methyltryptamine (5MeOMT). The kinetic constants for the methylation of MT are: K(MT) = 40 +/- 6, K(SAM) = 55 +/- 15, K(DMT) = 60, K(SAH) = 4.3 +/- 0.4 micromolar with unity interaction factors. The kinetic constants for the conversion of 5MeOMT to 5-methoxy-N,N-dimethyltryptamine (5MeODMT) are K(5MeOMT) = 40 +/- 10, K(SAM) = 90 +/- 40, and K(SAH) = 2.9 +/- 0.3 micromolar with unity interaction factors, except for SAM-5MeODMT = 2.0 +/- 0.9 and SAH-5MeOMT = 0.45 +/- 0.25. The kinetic constants for primary indolethylamine N-methyltransferase are K(m) (T) = 20, K(m) (SAM) = 40, K(i) (DMT) = 450 micromolar with the substrates binding independently.

Journal Article↗

PubMed1978

Bacteria from the gut of Australian termites.

The major gut bacteria of the worker caste of nine species of Australian termites, belonging to four families, were isolated and identified to generic level. All species were either facultative anaerobes or strict aerobes. A correlation appears to exist between the major gut bacterium and the family to which the termite belongs. The major bacterium from the two lowest termites, Mastotermes darwiniensis (family Mastotermitidae) and Cryptotermes primus (family Kalotermitidae), was Streptococcus; from four species belonging to the Rhinotermitidae (Heterotermes ferox, Coptotermes acinaciformis, C. lacteus, Schedorhinotermes intermedius intermedius) it was Enterobacter; and from three species of the Termitidae (Nasutitermes exitiosus, N. graveolus, N. walkeri) it was Staphylococcus. Enterobacter was a minor symbiont of M. darwiniensis, C. primus, and N. graveolus; Streptococcus was a minor symbiont of H. ferox, C. lacteus, S. intermedius intermedius, and N. exitiosus; and Bacillus was a minor symbiont of C. acinaciformis and S. intermedius intermedius. M. darwiniensis possessed another minor symbiont tentatively identified as Flavobacterium. C. acinaciformis from three widely separated locations possessed a similar microbiota, indicating some form of control on the composition of the gut bacteria. Bacteria, capable of growth on N-free medium in the presence of nitrogen gas, were isolated from all termites, except N. exitiosus and N. walkeri, and were identified as Enterobacter. No cellulose-degrading bacteria were isolated.

Animals↗

PubMed1978