Annual growth of the cockle Clinocardium ciliatum in the Norwegian Arctic (Svalbard area)

The Svalbard Islands are influenced by warm Atlantic water in the south and west, and cold Arctic water in the east. Ice cover, and hence the location of the highly productive marginal ice zone, varies both intra and interannually. Part of the primary production accumulates on the bottom and is utilized by the benthos. In this study, the annual growth of the cockle Clinocardium ciliatum (Fabricius, 1780) from three sites in Svalbard waters is reported. Moffen, the site in the north (80° 01 N, 13° 48 E) is located in the northernmost areas influenced by Atlantic water. The Storfjorden site (77° 10 N, 20° 09 E) is situated in cold Arctic water masses, and the Bear Island site (74° 50 N, 18° 54 E) is in the Polar front area where Atlantic and Arctic water masses meet. Annual growth of cockles was analysed retrospectively by measuring external growth increments, which gave annual growth records from the 1970s to 1996. Shell height for age for different year classes was highest at the Storfjorden site, and lowest at Bear Island. Periods of high growth occurred at Storfjorden and Bear Island during the 1980s while the beginning of 1990s was characterized by low growth. At Moffen, growth was more variable between single years. Several factors are influencing the growth of C. ciliatum in the Svalbard area and growth cannot be coupled to only one environmental factor like ice cover.     

Pre-moult foraging trips and moult locations of Emperor penguins at the Mawson Coast

The movements of nine breeding adult emperor penguins Aptenodytes forsteri from two colonies, Auster (67° 23S 64° 04E) and Taylor Glacier (67° 28S 60° 54E), were determined by satellite telemetry on their pre-moult foraging trips. While preparing for their annual moult the penguins travelled for 22–38 days and reached distances of up to 618 km from the colony. Six of the nine tracked penguins were followed to three different moult locations all to the west of their breeding colonies and near other known emperor penguins colonies, such as Kloa Point (66°38S, 59°23E) and Fold Island (67°17S, 59°23E). Sea-ice conditions changed throughout the tracking period; as the birds travelled north the sea-ice contracted south.     

Postembryonic development ofParalabidocera antarctica (I. C. Thompson) (Copepoda,Calanoida) from the fast ice near Syowa Station,Antarctica

Six nauplius and five copepodid stages as well as adults ofParalabidocera antarctica (I. C. Thompson, 1898) (Copepoda:Calanoida) are described based on specimens obtained from fast ice and collected by a plankton net near Syowa Station (69°00 S, 39° 35 E), Antarctica. The adult male and female are redescribed in detail. Nauplius stages ofP. antarctica are very similar to the previously describedAcartia species. Sexual dimorphism becomes apparent from copepodid IV onwards in the morphology of antennule and leg 5. The copepodid stages of this species retain certain characteristics not only of Acartiidae but also of Pontellidae and Parapontellidae.     

Observations on the reduction of non-activated carboxylates by Clostridium formicoaceticum with carbon monoxide or formate and the influence of various viologens

Crude extracts or supernatants of broken cells of Clostridium formicoaceticum reduce unbranched, branched, saturated and unsaturated carboxylates at the expense of carbon monoxide to the corresponding alcohols. The presence of viologens with redox potentials varying from E ₀=-295 to-650 mV decreased the rate of propionate reduction. The more the propionate reduction was diminished the more formate was formed from carbon monoxide. The lowest propionate reduction and highest formate formation was observed with methylviologen. The carbon-carbon double bond of E-2-methyl-butenoate was only hydrogenated when a viologen was present. Formate as electron donor led only in the presence of viologens to the formation of propanol from propionate. The reduction of propionate at the expense of a reduced viologen can be followed in cuvettes. With respect to propionate Michaelis Menten behavior was observed. Experiments are described which lead to the assumption that the carboxylates are reduced in a non-activated form. That would be new type of biological reduction.Non-standard abbreviations glc Gas liquid chromatography - HPLC high performance liquid chromatography - RP reverse phase; Mediators (the figures in parenthesis of the mediators are redox potentials E ₀ in mV) - CAV²⁺ carbamoylmethylviologen, 1,1-carbamoyl-4,4-dipyridinium dication (E ₀=-296 mV) - BV²⁺ benzylviologen, 1,1-dibenzyl-4,4-dipyridinium dication (E ₀=-360 mV) - MV methylviologen, 1,1-dimethyl-4,4-dipyridinium-dication (E ₀=-444 mV) - DMDQ²⁺ dimethyldiquat, 4,4-dimethyl-2,2-dipyridino-1,1-ethylendication (E ₀=-514 mV) - TMV²⁺ tetramethylviologen, 1,1,4,4-tetramethyl-4,4-dipyridinium dication (E ₀=-550 mV) - PDQ²⁺ propyldiquat, 2,2-dipyridino-1,1-propenyl dication (E ₀=-550 mV) - DMPDQ²⁺ dimethylpropyldiquat, 4,4-dimethyl-2,2-dipyridino-1,1-propenyl dication (E ₀=-656 mV) - PN productivity number=mmol product (obtained by the uptake of one pair of electrons) x (biocatalyst (dry weight) kg)^-1×h^-1     

Contribution to the rotifer fauna of subarctic Greenland (Kangerlussuaq and Ammassalik area)

Six water bodies in the region of Kangerlussuaq, West Greenland (67° 30 N, 50° 46 W), and four near Ammassalik, East Greenland (65° 36 N, 37° 38 W) were sampled. Sixty-nine taxa (2 Bdelloidea, 67 Monogononta) are reported, forty-six of which represent new records for Greenland. Proales pejleri n. sp. is described.     

Effect of nucleosides and nucleotides and the relationship between cellular adenosine 3′∶5′-cyclic monophosphate (cyclic AMP) and germ tube formation in Candida albicans

A yeast-mycelium (Y-M) transition in Candida albicans was induced by exogenous yeast extract, adenosine, adenosine 5-monophosphate (AMP), adenosine 5-diphosphate (ADP), adenosine 35 cyclic monophosphate (cAMP) and its analogue N⁶, O²-dibutyryl adenosine 35-cyclic monophosphate (dbcAMP) in defined liquid medium at 25°C. Adenosine 5-triphosphate (ATP) was found to delay germ tube formation in yeast cells, whereas the cAMP phosphodiesterase inhibitors, theophylline and caffeine, induced a Y-M transition. Intracellular and extracellular cyclic AMP levels increased during the yeast-mycelium transition and maximum levels of intracellular cyclic AMP coincided with maximum germ tube formation. Of the many inducers and inhibitors of germ tube and mycelium formation in C. albicans tested, including incubation at 37°C or in the presence of 1.5mM CaCl₂, the calmodulin inhibitor calmidazolium (R24571) added together with CaCl₂ induced the highest intra- and extracellular cyclic AMP levels. These results confirm the involvement of cyclic AMP in the yeast-mycelium transition of C. albicans.     

Population dynamics of the collared lemming and the tundra vole at Pearce Point,Northwest Territories,Canada

From 1987 to 1989 we monitored population changes during summer of the collared lemming (Dicrostonyx groenlandicus) and the tundra vole (Microtus oeconomus) at Pearce Point, Northwest Territories, Canada (69° 48 N, 122° 40 W). Populations on four study areas did not cycle but remained at low density (<3/ha) each year and continued at low numbers for the following 3 years (Reid et al. 1995). Lemming numbers often declined throghout the summer in spite of continous reproduction, and population recovery occurred overwinter. Heavy predation losses of radio-collared lemmings occurred each summer and this lemming population may be trapped in a predator-pit. Collared lemmings breed in winter and only because of winter population growth do these populations persist. Tundra vole numbers increased rapidly in most summers but usually declined overwinter. Tundra voles do not seem able to sustain winter reproduction in this extreme environment and this prevents them from reaching high density because of the short summer. Population growth in both these rodents could be prevented by poor food or by predation losses, and landscape patchiness may also help to prevent population growth. For lemmings we do not think that a shortage of shelter or intrinsic limitations could be restricting population increase at Pearce Point. This is the first detailed study of a non-cyclic collared lemming population.     

Phagostimulation of the mediterranean fruit fly, Ceratitis capitata by ribonucleotides and related compounds

Females of the medfly, Ceratitis capitata, prefer sucrose solutions containing ribonucleotides to sucrose solutions without them. The order of preference for the nucleotides was: 5GMP>GTP>5CMP>5IMP >dGMP>5UMP>5AMP>5XMP=ATP=2 & 3GMP=RP>3AMP.2AMP, guanosine, inosine, adenine and 5TMP produced no significant stimulation. Females sterilized by irradiation showed reduced attraction to 5GMP as compared to non-irradiated females.Optimal molecular configuration for phagostimulation includes: phosphorylation at the 5 position of the ribose, free hydroxyl groups at 2 and 3 on the ribose, and an NH₂ group at the 2 position of the aromatic ring of purine.It is proposed that the 5GMP in yeast hydrolyzate can be used as a measure of the suitability of the hydrolyzate as a bait.

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Résumé La femelle de la mouche méditerranéenne des fruits, Ceratitis capitata, préfère les solutions de sucrose contenant des ribonucléotides aux simples solutions de sucrose. Lórdre de préférence pour les nucléotides est le suivant: 5GMP>GTP>5CMP>5IMP >dGMP>5UMP>5AMP>5XMP=ATP =2 & 3GMP=RP>3AMP.Le 2AMP, la guanosine, l'inosine, l'adénine et le 5TMP provoquent une stimulation significative. Les femelles montrent aprés stérilisation par irradiation une attirance réduite pour le 5GMP par comparaison avec les femelles non-irradiées.La configuration moléculaire optimale pour la phagostimulation comprend: la phosphorylation en position 5 du ribose; des groupes hydroxyles libres en 2 et 3 sur le ribose; et un groupe NH₂ en position 2 sur le noyau aromatique.Nous proposons que le 5GMP dans l'hydrolysat de levure puisse être utilisé pour mesurer la capacité de l'hydrolysat comme appât.

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Abbreviations 5AMP Adenosine 5-monophosphate - 3AMP Adenosine 3-monophosphate - 2AMP Adenosine 2-monophosphate - dAMP 2-deoxyadenosine 5-monophosphate - ADP Adenosine 5-diphosphate - ATP Adenosine 5-triphosphate - 5GMP Guanosine 5-monophosphate - 2GMP Guanosine 2-monophosphate - 3GMP Guanosine 3-monophosphate - dGMP 2-deoxyguanosine 5-monophosphate - GDP Guanosine 5-diphosphate - GTP Guanosine 5-triphosphate - 5IMP Inosine 5-monophosphate - IDP Inosine 5-diphosphate - ITP Inosine 5-triphosphate - 5XMP Xanthosine 5-monophosphate - 5CMP Cytidine 5-monophosphate - dCMP 2 deoxycytidine 5-monophosphate - CTP Cytidine 5-triphosphate - 5UMP Uridine 5-monophosphate - 5TMP Thymidine 5-monophosphate - RP Ribose 5 monophosphate     

Identification of a codominant amplified polymorphic DNA marker linked to the verticillium wilt resistance gene in tomato

Resistance to verticillium wilt, a vascular disease causing yield losses in many crops, is conferred in tomato by a single dominant allele, Ve. A population segregating for the Ve allele was generated using near-isogenic tomato lines. Analysis of the parental tomato DNA using the polymerase chain reaction and 400 random primers, each 10 deoxyribonucleotides in length, produced 1,880 amplified DNA fragments. Of the four polymorphisms observed between the resistant and susceptible parental genotypes, only one was linked to the Ve gene. No recombination was observed between this DNA marker and the Ve locus, indicating that the linkage is less than 3.5±2.7 cM. The marker detected both the susceptible and resistant alleles, producing amplified DNA fragments of approximately 1,300 and 1,350 bp, respectively. The sequence of the primer, determined from cloned amplified products, was 5 CTCACATGCA 3 instead of the expected 5 CTCACATGCC 3. The marker will be of value to tomato breeding programs because of the tight linkage, Codominant nature, and analytical procedure utilized.     

The phytoplankton of Lake Liddell,New South Wales: chlorophyll a concentrations,species seasonal succession,and covariation with nutrients

Samples of the phytoplankton in a freshwater lake, Lake Liddell, New South Wales (Lat: 32° 22 S, Long. 150° 1 E) were collected every 4 weeks between October 1987 and November 1988. Chlorophyll a concentrations ranged from 1.8 g 1^–1 to 9.1 g 1^–1 and were positively correlated with the following nutrient parameters: total and nett mass additions of nitrate/nitrite-N and total-N, total additions of Kjeldahl-N, and nett mass addition N-P ratios. There was no correlation between lake nutrient concentrations and chlorophyll a. Factors other than nutrient concentrations appeared to be effecting chlorophyll a concentrations as summer levels were low despite nutrient concentrations being at a maximum. In spring and summer the phytoplankton was dominated by chlorophytes, with dinoflagellates and diatoms most abundant in autumn. During winter cyanobacteria were the most abundant. The relative abundance of chlorophytes was positively correlated with in lake nitrate/nitrite-N concentrations whereas the relative abundance of cyanobacteria was negatively correlated with this parameter. Based on chlorophyll a concentrations and the phytoplankton flora Lake Liddell can be classified as mesotrophic.     

Functional analysis of cis-elements, auxin response and early developmental profiles of the mannopine synthase bidirectional promoter

Summary The dual MAS1-2 promoter regulating two divergently transcribed mannopine synthase genes has been widely employed in plant expression vectors. As part of an effort towards its rational design as a genetic engineering tool, we have undertaken a functional analysis of the promoter by deletion mutagenesis and by the use of hybrid promoter constructs. Our results indicate that the central region of the intergenic promoter is composed of at least four domains. Three of these contain complementary sequences, which can potentially hybridize to form alternative palindromic structures. These three domains can function cooperatively, and in an orientation-independent manner, in imparting a sevenfold higher expression level at the 2 end relative to the corresponding 1. The remaining domain is characterized by tracts of repeated A/T-rich elements, and appears to confer the weak activity at the MAS1 promoter end. However, even though this A/T-rich DNA segment is functional, our deletion analysis provided strong evidence that it is completely dispensable for wild-type promoter activity. In addition, the relative distances between these enhancer domains and the 1–2 TATA-proximal regions can have a pronounced influence on the level of expression in both directions. In young tobacco seedlings, the two promoter ends are expressed in similar, if not identical, tissues in the aerial parts of the plants, but major differences can be observed in roots. Transient expression assays using hybrid promoter constructs showed that cis-elements that can respond to auxin induction signals are redundant in nature, in that they are dispersed throughout the promoter and showed no obvious consensus sequence.     

Ecological studies on Ulva lactuca L. from Veraval,India

Ulva lactuca L., at Veraval (20° 54N and 70° 22E) on the western coast of India, grows in the intertidal belt from June to late February. During the summer months of March, April and May, the species dries up, leaving rhizoidal fragments for perennation. High values of density, phytomass, frequency, weight, and volume have been recorded during September and January. Accumulation of phytomass appears to be chiefly density dependent. High dissolved oxygen content and low temperatures of the surface sea water favoured enhanced growth and, consequently, more phytomass.     

Photosynthetic activities of a membrane preparation of the thermophilic cyanobacterium Mastigocladus laminosus

Photosynthetically active membranes have been prepared from the thermophilic cyanobacterium Mastigogladus laminosus by treatment with lysozyme. The membranes were active in electron transport through photosystem I and II as well as in photophosphorylation and proton uptake. Cells were grown at 40°, 45° and 55°C respectively. The temperature optimum of oxygen evolution of whole cells was about 10°C higher than the growth temperature. In isolated membranes the temperature optimum for cyclic photophosphorylation was identical to the growth temperature of the cells whereas the optimum for photosystem II electron transport never exceeded 40°C. Photophosphorylation was inhibited by N, N-dicyclohexyl carbodiimide (DCCD), carbonyl-cyanide-m-chlorophenylhydrazone and NH₄Cl, whereas proton uptake was enhanced by DCCD. Electron transport was slightly inhibited by these treatments. The membranes could be stored for several weeks at-20°C in 50% glycerol without any loss in the activities.Abbreviations DPIP 2,6-dichlorophenolindophenol - CCCP Carbonyl-cyanide-m-chlorophenylhydrazone - DCCD N,N-dicyclohexyl carbodiimide - PMS N-methylphenazonium methosulfate - DCMU 3-(3-4-dichlorophenyl)-1,1-dimethylurea - TMP 20 mM Tris-HCl buffer pH 7.8, 10 mM MgCl₂, 5 mM phosphate buffer pH 7.8     

Observation of a distinct transition in the mode of interconversion of ring pucker conformers in non-crystalline d-ribose-2'-d from 2H NMR spin-alignment

Internal motions of d-ribose selectively ²H-labeled at the 2 position were measured using solid state ²H NMR experiments. A sample of d-ribose-2 -d was prepared in a hydrated, non-crystalline state to eliminate effects of crystal-packing. Between temperatures of –74 and –60°C the C2–H2 bond was observed to undergo two kinds of motions which were similar to those of C2–H2/H2 found previously in crystalline deoxythymidine (Hiyama et al. (1989) J. Am. Chem. Soc., 111, 8609–8613): (1) Nanosecond motion of small angular displacement with an apparent activation energy of 3.6 ± 0.7 kcal mol^–1, and (2) millisecond to microsecond motion of large amplitude with an apparent activation energy 4 kcal mol^–1. At –74°C, the slow, large-amplitude motion was best characterized as a two-site jump with a correlation time on the millisecond time scale, whereas at –60°C it was diffusive on the microsecond time scale. The slow, large-amplitude motions of the C2–H2 bond are most likely from interconversions between C2-endo and C3-endo by way of the O4-endo conformation, whereas the fast, small-amplitude motions are probably librations of the C2–H2 bond within the C2-endo and C3-endo potential energy minima.     

Reconstitution of cytoplasmic streaming inCharaceae

Summary The active sites of actin of oneCharaceae species were found to interact with the endoplasmic factor from a different species. Protoplasm was suqueezed out of cells ofChara australis with vacuoles that had been perfused beforehand with a medium containing EGTA and Mg · ATP. Centrifugation of this protoplasmic mixture divided it into the supernatant composed of endoplasmic granules and the precipitate composed of chloroplasts and nuclei. When the endoplasmic granular aggregates were introduced into a tonoplast-freeNitella axilliformis cell treated with NEM to inactivate the endoplasmic factor, they became attached to theNitella gel and streamed longitudinally with the polarity. Treatment of the endoplasmic granules with the strong Mg²⁺chelator CyDTA (1,2-cyclohexane diamineN, N-tetraacetic acid) irreversibly inhibited reconstitution of the cytoplasmic streaming.Abbreviations APW artificial pond water - ATP adenosine-5-triphosphoric acid - CyDTA cyclohexanediamine-N,N-tetraacetic acid - DTT dithiothreitol - EGTA ethyleneglycol-bis-(-aminoethylether)-N,N-tetraacetic acid - HMM heavy meromyosin - NEM N-ethylmaleimide - PEP phosphoenolypyruvate - PIPES piperazine-N,N-bis-(2-ethane-sulfonic acid) - PK pyruvate kinase - PMSF phenylmethylsulfonylfluoride     

Export and activity of hybrid FhuA''-''Iut receptor proteins and of truncated FhuA'' proteins of the outer membrane of Escherichia coli

Summary The FhuA protein in the outer membrane of Escherichia coli serves as a multifunctional receptor for the phages T5, T1, 80, for colicin M, for ferrichrome (Fe³⁺-siderophore) and for the structurally related antibiotic, albomycin. To determine structural domains required for these receptor functions and for export, a fusion protein between FhuA and Iut (receptor for Fe³⁺-aerobactin and cloacin DF13) was constructed. In the FhuA-Iut hybrid protein, 24 amino acids of FhuA were replaced by 19 amino acids, 18 of which were from Iut. The number of plaque forming units of phage T5 and T1 on cells expressing FhuA-Iut was nearly as high as on cells expressing plasmid-encoded wild-type FhuA. However, 10⁷-fold higher concentrations of phage 80 and 10³ times more colicin M were required to obtain a zone of growth inhibition. Truncated FhuA proteins in which the last 24 amino acids at the carboxy-terminus were replaced by 16 (FhuA2) or 3 (FhuAT) amino acids could hardly be detected on polyacrylamide electrophoretograms of outer membrane proteins, due to proteolytic degradation. Sensitivity of cells expressing FhuA2 to phage T5 and T1 was reduced by several orders of magnitude and sensitivity to phage 80 and colicin M was totally abolished. In contrast, cells expressing FhuAT were nearly as sensitive to phage T5, T1, and 80 and to colicin M as cells containing FhuA-Iut. None of the constructs could grow on ferrichrome as sole iron source and none was sensitive to albomycin. Ferrichrome did not inhibit binding of T5 to TonB^– cells expressing FhuA-Iut (as it did in FhuA⁺ cells) due to the lack of ferrichrome binding. It is concluded that very small deletions (relative to the size of FhuA with 714 amino acids) at the C-terminal end render FhuA susceptible to proteolytic cleavage. The C-terminal alterations affect sensitivity to FhuA-specific agents very differently. Apparently, the C-terminus is a very important part of FhuA regarding stability and activity. Expression of active FhuA and partially inactive FhuA derivatives in the same cell revealed no negative complementation, suggesting a FhuA monomer as functional unit.     

Correlation between testcross performance of lines at early and late selfing generations

Summary In hybrid breeding programs, testcross evaluation of lines can be done during the early stages of selfing (early testing) or delayed until the lines are near-homozygous. To evaluate the usefulness of early testing, the expected genetic and phenotypic correlations between testcross performance at different selfing generations were examined. The genetic correlation (r _GnGn ) between testcross performance of S _n and S _n , (n>n) individuals or lines is equal to the square root of the ratio of their testcross genetic variances, and it is a function of the inbreeding coefficients (F) at the two selfing generations, i.e., r _GnGn=[(1+F _n )/(1+F _n )]^0.5. The genetic correlation between testcross performance of lines and their directly descended homozygous (n=) lines is 0.71 for S₁; 0.87 for S₂, 0.93 for S₃, 0.97 for S₄, 0.98 for S₅, and 0.99 for S₅ lines. The effectiveness of early testing is limited mainly by nongenetic effects. The square root of testcross heritability at generation n sets the upper limit on the correlation between phenotypic value at generation n and genotypic value at homozygosity. The probabilities of correctly retaining S _n individuals or lines that have superior testcross performance at homozygosity (n=) indicate that early testing should be effective in identifying lines with above- and below-average combining ability. However, the risk of losing lines with superior combining ability is high if strong (best 10%) selection pressure is applied during early testing. If only a small proportion of lines is retained based on testcross performance and/or if the heritability of the trait is low, selfing for two or three generations prior to testcrossing may be desirable to increase the likelihood of retaining lines that perform well at homozygosity. The theoretical results in this study support the testcross evaluation procedures for grain yield used by most maize (Zea mays L.) breeders.A contribution from Limagrain Genetics, a Groupe Limagrain company     

Modulation of the beta-adrenergic-response in cultured rat heart cells

Summary Subcellular fractionation studies in resting human neutrophils indicated a bimodal distribution for cytochrome b. A. major peak of cytochrome b co-sedimented with gelatinase under different experimental conditions. This localization was partially overlapped with specific granules (using lysozyme and lactoferrin as specific granule markers), but clearly resolved from azurophilic granules, plasma membrane, mitochondria, as well as from a novel alkaline phosphatase-rich intracellular organelle. A minor localization of cytochrome b was found in fractions enriched in both the plasma membrane marker 5-nucleotidase and alkaline phosphatase. A significant portion of ubiquinone cell content co-fractionated with the gelatinase-containing granules. After phorbol myristate acetate (PMA)-cell stimulation, cytochrome b was mobilized to fractions showing respiratory burst activity and enriched in 5-nucleotidase activity. This mobilization paralleled secretion of gelatinase and lysozyme to the extracellular medium. Furthermore, neutrophil stimulation with fluoride in the absence of cytochalasin B induced release of gelatinase and generation of superoxide anion with only minimal release of lysozyme. Preincubation of cells with the anion channel blocker 4,4-diisothiocyanostilbene-2,2-disulfonic acid (DIDS) prevented lysozyme release, but had only a minor effect on the release of gelatinase and did not inhibit the superoxide anion generation elicited by N-formyl-methionyl-leucyl-phenylalanine or PMA. These results suggest a main location of cytochrome b in mobilizable gelatinase-containing granules, which can constitute a subpopulation of specific granules. Furthermore, these findings show that the gelatinase-containing granule is functionally involved in the respiratory burst in neutrophils and that membrane fusion between plasma membrane and the gelatinase-containing granule occurs during activation of cells.Abbreviations DIDS 4,4-diisothiocyanostilbene-2,2-disulfonic acid - FMLP N-formyl-methionyl-leucyl-phenylalanine - PMA 4-phorbol, 12-myristate, 13-acetate     

A New Aerobic Gram-Positive Bacterium with a Unique Ability to Degrade ortho- and para-chlorinated Biphenyls

Strain B51 capable of degrading polychlorinated biphenyls (PCB) was isolated from soil contaminated with wastes from the chemical industry. Based on its morphological and chemotaxonomic characteristics, the strain was identified as a Microbacterium sp. Experiments with washed cells showed that strain B51 is able to degrade ortho- and para-substituted mono-, di-, and trichlorinated biphenyls (MCB, DCB, and TCB, respectively). Unlike the known PCB degraders, Microbacterium sp. B51 is able to oxidize the ortho-chlorinated ring of 2,2-DCB and 2,4-DCB and the para-chlorinated ring of 4.4-DCB. The degradation of 2,4-DCB and 4,4-DCB was associated with the accumulation of 4-chlorobenzoic acid (4-CBA) in the medium in amounts comprising 80–90% of the theoretical yield. The strain was able to utilize 2-MCB, 2,2-DCB, and their intermediate 2-CBA and to oxidize the mono(ortho)-chlorinated ring of 2,4,2-TCB and the di(ortho-para)-chlorinated ring of 2,4,4-TCB. A mixed culture of Microbacterium sp. B51 and the 4-CBA-degrading bacterium Arthrobacter sp. H5 was found to grow well on 1 g/l 2,4-DCB as the sole source of carbon and energy.