George P. Sharples

Differentiation of Streptomyces coelicolor A3(2) under nitrate-limited conditions

The life cycle of Streptomyces coelicolor during development on solid medium has been studied from a physiological perspective. A biphasic growth pattern was demonstrated, evidenced by a continuous transition from an initial exponential growth period into a slower phase of biomass accretion. The switch between the two phases coincided with the exhaustion of nitrate from the medium. The depletion of nitrate from the medium coincided with the initiation of aerial mycelium formation within the cultures and the development of hydrophobic surface properties. During secondary growth, cultures remained metabolically active, continuing to accumulate DNA, despite a cessation in the levels of RMA and cell protein accretion. In addition, the accumulation of glycogen and lipid contributed to the observed accretion of biomass in this phase. The depletion of nitrate also marked an increase in the production of α-ketoglutarate by the culture and a coincident decrease in medium pH. Latter stages of the secondary growth phase saw the development of spores within the culture, this in turn was associated with a decrease in cellular glycogen. This supported previous observations that glycogen degradation and spore maturation were intimately associated.

Mechanical Properties of an Upgrading Cold-Mix Asphalt Using Waste Materials

AbstractConsiderable advantages could be achieved if the cold bituminous emulsion mixtures (CBEMs) show comparable engineering properties to hot-mix asphalt (HMA), particularly because CBEMs require no heat within the manufacture and laying process. As a result, such pavement produces less environmental impact, is more cost effective, and requires less energy consumption. This paper focuses on upgrading the CBEMs to a stage whereby their mechanical properties are comparable to traditional HMA. Waste or by-product materials were used within the CBEMs to improve the mechanical properties, namely indirect tensile stiffness modulus and creep stiffness. Five percentages from 0 to 5.5% of aggregate mass in the mixture of the LJMU-FA1 that is waste or by-product material was incorporated in the CBEMs. The results have illustrated a comparative enhancement in the mechanical properties of the new cold mixtures attributable to the use of the specific waste materials. Thus, new CBEMs having superior mechanical prope...

The importance of amino acids as carbon sources for Micromonospora echinospora (ATCC 15837)

Aims: This study set out to investigate the effect of amino acids on the uptake of glucose by Micromonospora eichinospora (ATCC 15837).

Response of Micromonospora echinospora (NCIMB 12744) spores to heat treatment with evidence of a heat activation phenomenon

P.A. HOSKISSON, G. HOBBS and G.P. SHARPLES.2000. The effects of heat treatment on spores of the actinomycete Micromonospora echinospora were investigated. The percentage of culturable spores in untreated spore stocks was found to be approximately 20%. A 60 °C treatment of spores in phosphate buffer for 10 min led to an approximately five‐fold increase in the number of culturable units. This indicated that a large proportion of the spores were constitutively dormant. Within 10 min and in the absence of an external energy‐yielding substrate, the heat treatment was found to stimulate spore respiration suggesting that endogenous storage compounds were being utilized. Heating spores at 70 °C shortened the time period required for activation; holding times greater than 10 min, however, resulted in a reduction of culturable cells. Classic thermal death characteristics were seen at temperatures of 80 °C and above with d‐values of 21·43, 2·67,0·45 and 0·09 min being recorded at 70, 80, 90 and 100 °C, respectively. Spores of this organism, while being weakly heat resistant in comparison with bacterial endospores, are significantly more resistant than vegetative cells.

Preliminary classification of characteristic organic gunshot residue compounds.

For the first time, a classification system for organic gunshot residue (OGSR) compounds with respect to the confirmation of OGSR materials is presented. There are 136 compounds considered to be associated with OGSR that have been highlighted in the literature. Many of these compounds could be classified as being ubiquitous in the environment and thus their detection as characteristic components of OGSR could cause issues with the interpretation of chemical ballistic evidence. The proposed system aims to address this problem by classifying OGSR compounds based on their forensic relevance with respect to the confirmation of GSR materials. To increase the forensic relevance of such a system, the large number of OGSR compounds reported in the literature has been decreased to 20 OGSR compounds based on the organic chemical composition of over 200 propellant powders. Occupational and environmental materials also associated with OGSR compounds have been considered.

Influence of medium composition on sporulation byStreptomyces coelicolor A3(2) grown on defined solid media

Reproducible sporulation using solid-plate cultures ofStreptomyces coelicolor A3(2) was obtained on a defined medium with glucose as the primary source of carbon and sodium nitrate as the sole source of nitrogen. The type of agar used as a solidifying agent, and the inclusion of trace salts to the medium, significantly affected sporulation. An interrelationship between the medium carbon to nitrogen ratio and sporulation was observed, with clear promotion of spore formation under nitrogen-limited conditions, whilst carbon-limited conditions suppressed sporulation. The influence of medium phosphate upon sporulation is also reported, with high concentrations exerting an inhibitory effect.

Spore formation in the Actinoplanaceae (Actinomycetales)

Spore development in four genera, Actinoplanes, Dactylosporangium, Planomonospora, and Streptosporangium, was studied by transmission and scanning electron microscopy. Actinoplanes and Streptosporangium formed spores by fragmentation of a hypha within its expanded outer sheath, as do many other actinomycetes. Dactylosporangium and Planomonospora formed spores endogenously by development of wall material within the parent hypha. In this respect, they resembled the genera Actinobifida and Thermoactinomyces. The term “sporangium” has therefore been used to describe structures which are not homologous. It was suggested that the term should be confined to structures in which endogenous spore formation occurs.

Xylariaceae on the Fringe

The Xylariaceae is one of the best-known pyrenomycete families (Ascomycota) and is distributed throughout the world. The majority are wood inhabitants and are prevalent in tropical and subtropical regions. Halorosellinia oceanicum is the most widely distributed in mangroves and can be regarded as truly manglicolous being frequently recorded as the dominant member of the family in such environments in S.E. Asia. In Malaysian mangroves, members of the Xylariaceae have been found to be numerically important with up to 9% present in one mangrove ecosystem. A further twelve xylariaceous genera are reported as occurring as their teleomorphs in mangrove forest and their immediate surroundings including Anthostomella, Astrocystis, Biscogniauxia, Camillea, Daldinia, Fasciatispora, Hypoxylon, Kretzschmaria, Nemania, Nipicola, Rosellinia and Xylaria. Furthermore, the presence of species from a number of these taxa, especially species of Anthostomella and Xylaria, are regularly isolated as endophytes from a variety of mangrove plant species. Mangrove Xylariaceae are also well known for their ability to produce novel and often bioactive metabolites.

Modulation of glycogen and trehalose levels in Micromonospora echinospora (ATCC 15837)

The growth of Micromonospora echinospora was studied in high and low C/N ratio medium using both batch and continuous culture. Asparagine was consumed rapidly in batch cultures where it served as both a nitrogen and carbon source. Glucose consumption was low suggesting that asparagine functions as the major carbon source under these conditions. The effect of nutrient limitation on the accumulation of storage carbohydrate in batch culture revealed an intimate association between nitrogen limitation and the accumulation of carbonaceous reserves. This study revealed that glycogen constituted the major carbohydrate reserve associated with the onset of sporulation. Intracellular trehalose levels were found to be relatively low and may have been affected by the availability of carbon. Continuous culture studies revealed a correlation between glycogen accumulation and increasing growth rate. It was also found that elevated cellular ATP levels correlated with the increase in glycogen, and reduced glycolytic activity. At the higher growth rates cellular ATP levels were elevated and coincided with reduced activity of the key glycolytic enzyme, phosphofructokinase, suggesting that glycogen can act as a convenient energy reservoir when excess carbon flux dictates.

Fate and Behavior of Gunshot Residue—A Review

A review of the literature concerning the fate and behavior of gunshot residue (GSR) is presented. A number of concomitant parameters including firearm and ammunition type, plume and GSR material characteristics, travel distances, chemical composition and GSR morphology are critically discussed in relation to their effects on the distribution and deposition, transfer and persistence processes of GSR. The underlying mechanisms associated with such processes are also considered. Knowledge of these processes on GSR materials could provide valuable information concerning scene preservation and subsequent forensic sampling. The number of GSR particles deposited can vary significantly with each firearm discharge, highlighting the potential to produce distinctive data in each individual case. With the continual development and compositional changes of new ammunition types, further evaluation of the effect these processes may have on GSR evidence and their possible influence on the interpretation of the analytical results should be given due consideration.