Role of membrane potential in ammonium inhibition of nitrogenase activity in the cultured cyanobiont Nostoc ANTH

Ammonium at 5mM completely inhibited nitrogenase activity of Nostoc ANTH but only slightly inhibited the membrane potential, indicating that these two events are independent and that nitrogenase activity is not regulated by the latter.B.B. Singh and P.S. Bisen are with the Department of Microbiology, Barkatullah University, Bhopal-462026, India; S. Singh was with the Department of Microbiology, Barkatullah University, Bhopal, India; he is now with the Department of Microbiology, North Maharastra University, Jalgaom-425001, India.     

Continuous production of lactic acid from molasses by free and immobilized Sporolactobacillus cellulosolvens

Both free and immobilized cells of Sporolactobacillus cellulosolvens, in continuous culture on molasses (50 g sugar 1^-1) at 40°C, had maximum lactic acid productivities of 0.03 and 0.06 mol l^-1 h, at dilution rates of 0.27 and 0.25 h^-1, respectively.S.S. Kanwar is with the Department of Biotechnology, Guru Nanak Dev University, Amritsar-143 005, India; B.S. Chadha is with the Department of Microbiology, Guru Nanak Dev University, Amritsar-143 005, India. H.K. Tewari and V.K. Sharma are with the Department of Microbiology, Punjab Agricultural University, Ludhiana-141 004, India.     

Ultrastructural changes during wood decay by Antrodiella sp. RK1

Southern yellow pine (softwood) and maple (hardwood) wood decayed for 12 weeks by Antrodiella sp. RK1 had average weight losses of 20 and 19%, respectively, and approximately 34 to 35% lignin loss. The ratio of percentage lignin loss to glucose loss was 3.6 and 2.7 for softwood and hardwood, respectively. There was negligible loss of other wood sugars such as xylose, arabinose, galactose and mannose. Scanning electron microscopy revealed the presence of erosion troughs and bore holes in decayed samples of both softwood and hardwood. Secondary walls were void of lignin, middle lamella and cell corners were extensively decayed. Ca²⁺ crystals were abundantly present in the areas of decay. Transmission electron micrographs revealed the presence of hyphal sheath and growth of hyphae directly through the cell corners.R.N. Patel and K.K. Rao are with the Department of Microbiology & Biotechnology Center, Faculty of Science, M.S. University of Baroda, Baroda-390 002, India.     

A new species of Gigaspora from desert soils of Rajasthan,India

A new species of the endogonaceous fungus Gigaspora, isolated from the Indian semi-arid region, is described. The fungus, named G. tuberculata, produces rusty-brown azygospores with septate subtending hypha. The azygospores bear warts all over the outer wall. The shape, size and general appearance of these spores resemble those of Scutellospora persica.Neeraj and A.K. Varma are with the Microbiology Unit, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India; K.G. Mukerji is with the Applied Mycology Laboratory, Botany Department, University of Delhi, Delhi 110 006, India. B.C. Sharma is with the Department of Textile Engineering, Indian Institute of Technology, New Delhi 110 016, India.     

Root exudation from Leucaena leucocephala in relation to mycorrhizal colonization

Lower amounts of root eduxates (13 mg/g dry root) emerged from leucaena plants inoculated with the mycorrhizal fungus, Glomus fasciculatum, than uninoculated plants (21 mg/g dry root). Mycorrhizal plants exuded less K⁺, P_i and sugars (mainly glucose) but more protein, nitrogen, phenolics and gibberellins than uninoculated plants. Glycine, alanine, cysteine, arginine, tryptophan and valine occurred only in the root exudates of the former. Uninoculated plants exuded more of a root-elongation inhibitory substance than the uninoculated ones.R.J. Mada and D.J. Bagyaraj are with the Department of Agricultural Microbiology, University of Agricultural Sciences, GKVK Campus, Bangalore 560065, India.     

Distribution of Bacillus thuringiensis strains in Southern Sweden

Bacillus thuringiensis strains were found to be naturally present in the soils of southern Sweden, being isolated from nine out of 12 sites examined. Forest soil samples were more rich in B. thuringiensis strains than soil samples collected from cultivated areas. A wide diversity of B. thuringiensis strains, representing different biochemical groups, was isolated; samples from Aspö and Fogdö regions showed the highest degree of diversity.R. Landén and M. Bryne are with the Department of Microbiology, Stockholm University, S-10691 Stockholm, Sweden. A. Abdel-Hameed is with the Department of Microbiology, Faculty of Pharmacy, Cairo University, Kasr-El-Aini Street, Cairo, Egypt. A. Abdel-Hameed's present address is the Department of Applied Chemistry and Microbiology, PO Box 27, Viikki, Building B, SF-00014 University of Helsinki, Helsinki, Finland     

Assimilation of ethylenediamine as nitrogen source by the cyanobiont Nostoc ANTH

Nostoc ANTH metabolizes ethylenediamine (EDA) as sole nitrogen source but not as a carbon source. EDA is assimilated by the glutamine synthetase-glutamate synthase pathway. EDA represses heterocyst formation and nitrogenase activity but this is reversed by l-methionine-dl-sulphoximine.The authors are with the Department of Microbiology, Barkatullah University, Bhopal 462 026, India     

Influence of growth conditions on the accumulation of ergosterol by Rhodotorula glutinis

Maximum accumulation of ergosterol by Rhodotorula glutinis IIP-30 [4% (w/w) of the biomass] was at pH 4 and 28 to 30°C, wich glucose or sucrose as carbon source and (NH₄)₂SO₄ as N-source. Molasses only gave 1% (w/w) ergosterol content, as did KNO₃ or urea when used as sole N source.V.W. Johnson was and N.K. Yadav is with the Microbiology Department, School of Science, Gujarat University, Ahmedabad 380 009, India. V.W. Johnson is now with the Blotechnology Laboratory, Research Centre, Gujarat State Fertillizers Company Ltd, Baroda 391 750, India. M. Singh was with the Applied Biology Laboratory, Research Centre, Indian Petrochemicals Corporation Ltd, Baroda 391 345, India, and is now with Pfizer Limited, 178, Industrial Area, Chandigarh 160 002, India.     

Glutamine synthetase and arginine inhibition of nitrate reductase activity in Anabaena cycadeae

Wild-type Anabaena cycadeae with normal glutamine synthetase (GS) activity utilized arginine as sole N source whereas a mutant strain lacking GS activity did not. Nitrate reductase (NR) activity, higher in the mutant strain than the wild-type strain, was inhibited by arginine though arginine-dependent NH ₄ ⁺ generation was higher in the mutant strain than in the wild-type. This suggests that (1) NR activity is NO _inf3 ^sup- -inducible and arginine-repressible; and (2) while GS activity is required for the assimilation of arginine as sole N-source, it is not required for arginine inhibition of NR activity.S. Singh was with the Department of Biochemistry, North-Eastern Hill University, Shillong-793014, India, and is now with P.S. Bisen at the Department of Microbiology, Barkatullah University, Bhopal-462026, India     

De-regulated assimilation and over-production of amino acids in analogue-resistant mutants of a cyanobacterium,Phormidium uncinatum

Mutant strains of Phormidium uncinatum resistant to fluoro-phenylalanine, aztryptophan, fluorotyrosine and azaleucine accumulated a wide range of amino acids, notably glutamic acid, lysine, tyrosine and phenylalanine, and exhibited de-regulated valine and phenylalanine transport. While acetohydroxy acid synthase in azaleucine-resistant mutants lost valine- and leucine-sensitivity, 3-deoxy-Dxxx-arabinoheplulosonate-7-phosphate (DAHP) synthase and prephenate dehydratase in aromatic analogue-resistant strains became phenylalanine-insensitive and shikimate and prephenate dehydrogenases were activated by tyrosine. In addition, activities of nitrate-assimilating enzymes were higher in the mutants, which also exhibited increased nitrogen, protein and phycocyanin contents. The proteins in the mutants were better digested upon enzymatic-treatments and feeding trials than those of the wild type, indicating that they are usable as single-cell protein.N.S. Rao and T.M. Shakila are and S.N. Bagchi was with the Department of Biological Sciences, R.D. University, Jabalpur-482 001, Madhya Pradesh, India. S.N. Bagchi is now with the Department of Microbiology, MDS University, Amjer-305 001, Rajasthan, India.     

Toxicity of the blue-green alga Oscillatoria agardhii to the mosquito Aedes aegypti and the shrimp Artemia salina

The cyanobacterium Oscillatoria agardhii 27, which does not produce mammalian neuro- or hepatotoxins, was highly toxic to the larval stages of the yellow fever mosquito Aedes aegypti: its 24-h LC₅₀ values against fourth-and second-instar larvae of A. aegypti were 8.7 and 6.1 g live cells/ml, respectively. The toxin was water-soluble and was partially purified but the chemical nature of the toxic compound(s) is still unknown. Aqueous solutions were also toxic to the newborn larvae of the brine shrimp, Artemia salina, used for the bioassay. The toxic activity of these solutions decreased markedly on heating to 90°C for 15 min.J. Kiviranta is with the Department of Pharmacy, P.O. Box 15, FIN-00014 University of Helsinki, Helsinki, Finland; A. Abdel-Hameed is usually with the Department of Microbiology, Faculty of Pharmacy, Cairo University, Kasr-El-Aini Street, Cairo, Egypt, but is presently with the Department of Applied Chemistry and Microbiology, P.O. Box 27, Viikki, Building B, FIN-00014 University of Helsinki, Helsinki, Finland.     

Studies on Bacillus thuringiensis strains isolated from Swedish soils: insect toxicity and production of B. cereus-diarrhoeal-type enterotoxin

At moderate concentration, 23 of 40 strains of Bacillus thuringiensis isolated from Sweden were toxic to Trichoplusia ni and five were toxic to Aedes aegypti. Five of the strains were toxic to Diabrotica undecimpunctata at high concentration, two were toxic to Heliothis virescens at low concentration and five produced thuringiensin (formerly called -exotoxin). No strain was toxic towards the beet armyworm Spodoptera exigua at low concentration. Twenty-three of the strains produced a B. cereus-diarrhoeal-type enterotoxin.A. Abdel-Hameed is with the Department of Microbiology, Faculty of Pharmacy, Cairo University, Kasr-El-Aini Street, Cairo, Egypt. R. Landén is with the Department of Microbiology, Stockholm University, S-10691 Stockholm, Sweden. A. Abdel-Hameed's present address is the Department of Applied Chemistry and Microbiology, P. O. Box 27, Viikki, Building B, FIN-00014 University of Helsinki;     

Glucose metabolism and polysaccharide accumulation in the marine bacterium,Shewanella colwelliana

Shewanella colwelliana, a marine bacterium isolated in association with the oyster Crassostrea virginica, produces an abundant exopolysaccharide with potential commercial value as an adhesive under aqueous conditions. Its utilization of glucose was modulated by stoichiometric concentrations of yeast extract. In Brain Heart Infusion medium containing glucose, growth was diauxic with delayed glucose utilization and incorporation into exopolysaccharide. Data from radio-respirometry protocols indicate that glucose is catabolized through a combination of the hexose monophosphate and Entner-Doudoroff pathways. Exopolysaccharide production could be significantly enhanced by adjusting glucose concentrations of the growth medium.G.O. Abu was and R. Weiner and R.R. Colwell are with the Department of Microbiology, University of Maryland, College Park, MD 20742, USA. G. O. Abu is now with the Department of Microbiology, University of Port Harcourt, P.M.B. 5323, PH, Nigeria.     

Hydroxylation of progesterone by Cunninghamella blakesleeana NCIM 687

Progesterone was completely hydroxylated, principally to 11,14 dihydroxyprogesterone by Cunninghamella blakesleeana NCIM 687 in 48h.S.B. Chincholkar is with the Microbiology Division, Department of Life Sciences, North Maharashtra University, Jalgaon 425 001, India. R. Seeta Laxman is with the Division of Biochemical Sciences, National Chemical Laboratory, Pune 411 008, India. R.D. Wakharkar is with Organic Chemistry. Technology Division, National Chemical Laboratory, Pune 411 008. India     

Novel screening assay for the detection of phenolic acid esterases

A novel plate assay method, developed for the screening of microorganisms or enzyme preparations for phenolic acid esterases, involves incorporating ethyl cinnamate into an agar medium. After inoculation and incubation, the plate is flooded with a pH-sensitive dye to reveal yellow zones around positive cultures against a blue background. A number of yeasts (Rhodotorula spp. and Candida spp.) and fungi (Penicillium sp. and Aspergillus sp.) gave positive results, while a number of commercial enzymes, particularly pectinases, also exhibited good phenolic acid esterase.J.A. Donaghy and A.M. McKay are with the Food Microbiology Research Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX, UK. A.M. McKay is also with the Department of Food Science (Microbiology), The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX, UK.     

Influence of nitrogen source on hydrogen generation by a photosynthetic bacterium

Axenic culture of photosynthetic purple sulphur bacterium, isolated from a paper mill effluent, grew best with ammonium chloride as nitrogen source. Cells grown with N₂ or ammonium chloride produced hydrogen with initial lag periods of 24 and 48 h, respectively. The maximum amount of hydrogen was evolved by cells grown with N₂ and with malate as electron donor.R. Lakshmi is with the Microbial Physiology Laboratory, Department of Botany, and H. Polasa is with the Department of Microbiology, Osmania University, Hyderabad 500 007, India.     

High ethanol productivity from lactose by immobilized cells of Kluyveromyces fragilis and Zymomonas mobilis

Ethanol production from 200 g lactose/l by Kluyveromyces fragilis immobilized in calcium alginate was 63 g/l whereas with co-immobilized K. fragilis and Zymomonas mobilis 72 g ethanol/l was attained. With free cells of K. fragilis, only 52 g ethanol/l was obtained. The beads were relatively stable without significant reduction in activity for about six batches of fermentation.The authors are with the Department of Microbiology and Microbial Technology, School of Biological Sciences, Madurai Kamaraj University, Madurai 625 021, India.This paper is dedicated to Professor M. Lakshmanan, Vice-Chancellor, Madurai Kamaraj University, in commemoration of his 60th birthday.     

Bacillus fermentation of soybeans

Kinema fermentations of Indian and Canadian No. 1 soybeans by Bacillus sp. DK-W1 and by mixed cultures of Bacillus sp. DK-W1 and Enterococcus faecium DK-C1 were essentially identical. The viable cell count of Bacillus increased from an initial 10⁵ to 10¹⁰ c.f.u./g wet wt after 48 h incubation at 37°C. The pH of the fermentation dropped from an initial 6.9 to about 6.4 after 8 h and then rose to 8.6 after 32 h, with a coincident increase in proteolytic activity and ammonia concentration. The fermentations containing E. faecium and Bacillus exhibited a greater initial pH decline and a slightly retarded subseqent increase in pH compared with fermentations with Bacillus only. The presence of E. faecium had no detectable effects on growth of the Bacillus, proteolytic activity, ammonia production or the final pH of the fermentations.P.K. Sarkar was and P.E. Cook and J.D. Owens are with the Food Microbial Interactions Laboratory, Department of Food Science and Technology, University of Reading, Reading RG6 2AP, UK; P.K. Sarkar is now with the Microbiology Laboratory, Centre for Life Sciences, University of North Bengal, Siliguri 734430, India.     

Light-independent conidiation in Trichoderma spp.: a novel approach to microcycle conidiation

Microcycle conidiation in Trichoderma hamatum and T. harzianum has been achieved in complete darkness for the first time. The time required for mass conidiation without intervening vegetative growth was decreased to 24 h instead of 6 to 7 days. The conidia produced by microcycle conidiation were viable and had pigmentation and antagonistic behaviour similar to those of the parental stock cultures.N. Khurana, R.K. Saxena, R. Gupta and R.C. Kuhad are with the Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi-110021, India.     

Effects of genotoxic agents on his + revertants and survival of spores of Streptomyces aureofaciens

The effects of u.v. light and of several chemical agents on spores of the tetracycline producer Streptomyces aureofaciens MT1 were studied using survival curves and induction of histidine prototrophic revertants (his ⁺). Spores were highly resistant to u.v.; NTG induced most his ⁺ revertants. 4-Nitroquinoline-1-oxide and methyl methanesulphonate also gave good yields of revertants. Whereas ethyl methanesulphonate had the least effect on inducing the revertants.M. Marins is with the Department of Biochemistry, Institute of Chemistry, University of São Paulo, SP, Brazil. S.O.P. Costa and G. Padilla are with the Department of Microbiology, Biomedical Science Institute, University of São Paulo, Avenida Prof. Lineu Prestes 1374, SP, Brazil, CEP 05508-900