Molecular cloning of Bacillus polymyxa (1→4)-β-d-xylanase gene in Escherichia coli

Escherichia coli has been transformed with recombinant plasmids carrying DNA from Bacillus polymyxa. A sensitive and simple immunoassay was used to screen for E. coli transformed with the chimeric plasmid carrying a (1→4)-β-d-xylanase (1,4-β-d-xylan xylanohydrolase, EC 3.2.1.8) gene. One such clone was isolated. The enzyme present in extracts of these E. coli cells was active in catalysing the hydrolysis of (1→4)-β-d-xylo-oligosaccharides of identified structure from the mucilage of Plantago ovata Forsk, as indicated by the production of reducing sugars. This work holds promise for the large-scale production of xylanases as a new route to the economic and usable degradation of xylans and is a model for the large-scale production of enzymes.     

Laccase production by polyporus versicolor on different substrates

Extracellular production of laccase (E.C. 1.10.3.2) by Polyporus versicolor was studied on lignin, complex and defined media. Although the production of enzyme was more on lignin the specific activity was more on malt extract. Laccase was produced on all the media tested i.e. phenolic compounds, lignins and sugars alone, and in combination with malt extract, excepting salicylic acid. On single source media maximum yields of enzyme were obtained on polyfon followed by resorcinol, reax and lignin. As compared to phenolic compounds the enzyme production was low on sugars. Addition of malt extract enhanced the enzyme yield which was maximum in the case of lignin followed by gallic acid.     

Aerobic degradation of choline by Proteus mirabilis: enzymatic requirements and pathway

Cleavage of choline to trimethylamine and acetaldehyde by extracts of Proteus mirabilis requires both particulate and soluble protein fractions, K+, and a bound divalent metal cation. The reaction shows a long lag period, abolished only by preincubation of the particulate fraction in the complete reaction system. The two-carbon fragment produced is acetaldehyde; choline cleavage appears to be tightly coupled to dismutation of the acetaldehyde to ethanol and acetate, as indicated by stimulation by NAD+, ADP, and Fe2+ and inhibition by reagents reacting with acetaldehyde. The system is thus similar to that previously described in anaerobes (Desulfovibrio, Clostridium). Attempts to demonstrate a cobamide coenzyme requirement (as in the similar ethanolamine ammonia-lyase reaction) were unsuccessful; the reaction was carried out by fractions devoid of vitamin B12 activity (not supporting growth of Lactobacillus leichmannii) and insensitive to light.     

Clastogenicity evaluation of seven chemicals commonly found at hazardous industrial waste sites

7 chemicals commonly found at the industrial waste sites were tested with the Tradescantia-Micronucleus (Trad-MCN) assay to evaluate their clastogenic potential. Chemicals selected from the US EPA Superfund Priority 1 list were: aldrin, arsenic trioxide, 1,2-benz[a, h]anthracene, dieldrin, heptachlor, lead tetraacetate and tetrachloroethylene. Results of repeated tests for clastogenicity yielded the minimum effective dose (MED) for clastogenicity of 0.44 ppm for lead tetraacetate, 1.88 ppm for heptaclor, 3.81 ppm for dieldrin and arsenic trioxide and 1,2-benz[a, h]anthracene yielded positive responses at the MED of 3.96 ppm and 12.50 ppm respectively. Aldrin and tetrachloroethylene were considered to be immiscible with water, and the tests yielded negative responses. Tetrachloroethylene in gaseous state was also used to treat the flower buds. Results of tetrachloroethylene vapor phase treatment yielded a positive response at the MED of 30 ppm/min after a 2-h exposure. 5 chemicals determined to be clastogens by this test were ranked according to their MED in the descending order of potency as follows: lead tetraacetate, heptachlor, dieldrin, arsenic trioxide and 1,2-benz[a, h]anthracene. Results of this study indicate that the Trad-MCN bioassay could be effectively utilized for assessing the potential clastogenicity of the chemicals commonly found at the industrial hazardous waste sites.     

The role of supporting ecosystem services in conventional and organic arable farmland

Ecosystem services (ES) in agriculture are vital for the sustainable supply of food and fibre, but their economic value has rarely been evaluated in agricultural crops at field level. The current study quantified three key supporting ES associated with highly modified arable landscapes in New Zealand using a novel, experimental ‘bottom-up’ approach. These services were biological control of pests, soil formation and the mineralisation of plant nutrients. The results showed that background (unmanipulated) biological control of pests in conventional arable farming were severely and significantly reduced compared with fields under organic management. ES associated with soil formation and mineralisation of plant nutrients did not differ significantly between organic and conventional fields. This study also estimated the economic value of these services using experimental data, in contrast with ‘value transfer’ approaches used in previous studies. The total economic value of these three ES was significantly higher in organic fields as compared to conventional ones. Yields obtained in organic fields were similar to those in conventional ones. This work quantified the role that land management practices play in the maintenance and enhancement of supporting ES in agricultural land and showed that conventional New Zealand arable farming practices can severely reduce the ecological and financial contribution of some of these services in agriculture.