Synergistic growth of two members from a mixed microbial consortium growing on biphenyl

Abstract A stable nine-membered aerobic bacterial consortium (BSEN-2) growing on biphenyl as the sole carbon and energy source was isolated from a polychlorinated biphenyl (PCB) contaminated soil. Characterisation of the members, strains BPSI-1 to 9, revealed three principal genera, Pseudomonas, Sphingomonas and Alcaligenes . Phenotypic analysis based on standard microbiological tests and Biolog identification, showed close relationship between community members with the exception of Sphingomonas paucimobilis strain BPSI-3. Some clusters revealed relationships unrelated to genus groupings. Strain BPSI-3 produced a bright yellow water soluble compound from biphenyl having absorption maxima at 412 and 337 nm at neutral pH. This is similar, but not identical, to those results reported for muconic semialdehydes, cleavage products of biphenyl and other aromatic compounds. Only four of the nine isolates, BPSI-2, 3, 4 and 7, were capable of growth on biphenyl as sole carbon and energy source. Two isolates, Alcaligenes faecalis type II strain BPSI-2 and S. paucimobilis strain BPSI-3, were isolated together and were difficult to separate into pure cultures. Growth studies in liquid culture showed that a co-culture of these two achieved a specific growth rate (μ) approximately twice as high as strain BPSI-2 and four times that of BPSI-3. Both strains grew equally well on benzoate with no significant difference in their specific growth rates. When compared to the original mixed culture, BSEN-2, the co-culture achieved 39% greater biomass and a specific growth rate twice as high. In the co-culture, the yellow colour seen with pure cultures of BPSI-3 was not observed. BPSI-2 was found to be able to utilise the yellow metabolites more effectively than BPSI-3. A model for the interaction of these two strains, based on the utilisation of biphenyl catabolites and degradation at the genetic level, has been proposed.     

Increasing the accuracy of surface area estimation using single wax dipping of coral fragments

The measurement of coral surface area is critical to normalising a suit of physiologically significant parameters to greater understand how corals interact with the surrounding environment. The surface area detection from skeletal fragments subsequently needs to be both as accurate as possible, yet practical and robust enough to be performed with minimal laboratory equipment. By using X-Ray CT technology, as a highly accurate surface area standard, 12 coral specimens from 4 different genera were studied using single wax versus double wax dipping methods. Our results reveal that the single wax dipping is far more accurate than the more commonly practised double wax dipping, thereby leading to more accurate estimation of the physiologically active surface.     

Antimicrobial properties of secretions from the metapleural glands of Myrmecia gulosa (the Australian bull ant)

D.A. VEAL, J.E. TRIMBLE AND A.J. BEATTIE. 1992. Myrmecia gulose (Australian bull ant) produce secretions from their metapleural exocrine glands which have broad spectrum antimicrobial properties. Such secretions are probably of importance in disease control in bull ant communities. These antimicrobial secretions are stable at 100°C, resistant to proteolytic enzymes and are active over a wide pH range. Of the organisms tested only endospores of Bacillus cereus were found to be resistant. The antimicrobial agent(s) are absorbed by cells and result in cell lysis. The secretions do not interfere with any growth-related processes. These observations demonstrate that insects may be a source of novel antimicrobial agent(s).     

Storage of a mixed microbial consortium capable of growth on biphenyl

A mixed microbial consortium, BSEN-2, was isolated from a polychlorinated biphenyl-contaminated soil using biphenyl as the sole source of carbon and energy. The community was found to contain nine members based on colony morphology on plate count agar with biphenyl. BSEN-2 was stored on glycerol (15% v/v) at - 80°C and was regenerated 3, 30, 100 and 250 d after freezing. No loss of community members or significant change in growth kinetics were observed. This method provides a simple, convenient and reliable method of producing mixed microbial inocula.     

Superoxide dismutase and cytochrome oxidase in collapsed lungs: possible role in reexpansion edema

This study examined the effects of lung collapse, a condition that causes relative hypoxia in lung tissues, on superoxide dismutase (SOD), cytochrome oxidase (cyt ox), and pyruvate kinase (py ki) activities in rabbits. Cyanide-insensitive respiration measurements were done in collapsed and contralateral lungs, as an index of intracellular free radical production. Rabbits' right lungs were collapsed for 7 days after which the animals were killed. We found that control rabbit lungs contained approximately 25 SOD units/mg DNA measured with 10(-5) M KCN (total SOD) and approximately 11 SOD units/mg DNA measured with 10(-3) M KCN (mitochondrial or MnSOD). Right lung collapse caused a 25% decrease in mitochondrial SOD activity after 7 days (P less than 0.05), whereas no significant changes occurred in right or left lungs' total SOD activity. In control rabbits cyt ox activity averaged approximately 0.009 mumol ferrocytochrome c.min-1.mg DNA-1. Right lung collapse caused a greater than 40% decrease in cyt ox activity after 7 days of collapse (P less than 0.05), whereas cyt ox activity in contralateral left lungs did not change. Pyruvate kinase activity, a marker for anaerobic glycolysis resulting from tissue hypoxia, increased 49% in collapsed right lungs (P less than 0.01). Cyanide-insensitive respiration was 83% higher in 7 day-collapsed lungs (2.28 +/- 0.66 microliters O2.min-1.g-1) compared with contralateral lungs (1.24 +/- 0.34, P less than 0.05), indicating increased O2-. and H2O2 production in this tissue after homogenization at normoxic PO2 (approximately 150 Torr).(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of fluorochromes for flow cytometric detection of Cryptosporidium parvum oocysts labelled by fluorescent in situ hybridization

Oligonucleotide probes specific to Cryptosporidium parvum (CRY1) were conjugated with a range of fluorochromes. The fluorescence after in situ hybridization (FISH) labelling of oocysts and controls was assessed. The objective was to determine the most suitable conjugate for FISH labelling, followed by analysis with a 488 nm laser flow cytometer. The most promising candidate was fluorescein isothiocyanate but only when linked to the CRY1 probe via an 18-carbon spacer arm consisting of six ethylene glycol moieties. The use of the spacer increased fluorescent signals fivefold compared with an equivalent probe in which the FITC was linked directly to the 5'-amino group of the DNA.