Linking the bacterial community in pea aphids with host-plant use and natural enemy resistance

Abstract.  1. Pea aphids, Acyrthosiphon pisum , harbour a range of facultative accessory bacteria (secondary symbionts), including those informally known as PASS (R-type), PAR, PABS (T-type), and PAUS (U-type).
2. To explore the relationship between possession of these bacteria and ecologically important traits of A. pisum , correlations between the accessory bacteria found in 47 parthenogenetic clones of A. pisum and the host plant on which each clone was collected and its susceptibility to natural enemies were surveyed.
3. The bacterial complement varied with plant of collection. PAUS (U) was present in all of 12 clones affiliated to Trifolium but was otherwise rare, while PABS (T) and PASS (R) occurred at significantly higher frequency in clones from Lotus and Vicia , respectively, than clones from other plants.
4. Possession of PABS (T) was associated strongly with resistance to the parasitoid Aphidius eadyi and weakly with resistance to Aphidius ervi . Aphids carrying PAUS (U) were more resistant to the fungal pathogen Pandora ( Erynia ) neoaphidis , although this correlation was complicated by a strong association with host-plant use.     

Isolation and identification of synthetic pyrethroid-degrading bacteria

AIMS: To isolate, select, identify and assess the potential for the biodegradation of synthetic pyrethroids (SPs) in sheep dips. METHODS AND RESULTS: SP-degrading bacteria were isolated from a mixed soil sample consisting of garden soil and soils from farms where SPs had been used. The two largest in size were then identified using microscopy, biochemical and genetic techniques to be members of the genera Pseudomonas and Serratia. By comparing the 16S rRNA gene sequences, the Pseudomonas sp. discovered was shown to group within the Pseudomonas fluorescens intrageneric cluster. The Serratia isolated was closely related to Serratia plymuthica. Cell growth and degradation was greatest in the Pseudomonas sp. culture where there was breakdown of 60 mg l(-1) to 6 mg l(-1) technical cypermethrin in 20 days. Tolerance to the SPs was greater in the Pseudomonas sp. but was found to depend on the availability of other carbon sources and nutrients. CONCLUSIONS: The bacteria characterized show the potential to be used in a bioremediation application for the treatment of SP residues. SIGNIFICANCE AND IMPACT OF THE STUDY: The SP-degrading bacteria may have use in the disposal of used SP residues and with further research could lead to an alternative route of disposal for use in agriculture or industry.     

S-adenosylmethionine (SAMe) modulates interleukin-10 and interleukin-6, but not TNF, production via the adenosine (A2) receptor

S-adenosylmethionine (SAMe) is the first product in methionine metabolism and serves as a precursor for glutathione (GSH) as well as a methyl donor in most transmethylation reactions. The administration of exogenous SAMe has beneficial effects in many types of liver diseases. One mechanism for the hepatoprotective action is its ability to regulate the immune system by modulating cytokine production from LPS stimulated monocytes. In the present study, we investigated possible mechanism(s) by which exogenous SAMe supplementation modulated production of TNF, IL-10 and IL-6 in LPS stimulated RAW 264.7 cells, a murine monocyte cell line. Our results demonstrated that exogenous SAMe supplementation inhibited TNF production but enhanced both IL-10 and IL-6 production. SAMe increased intracellular GSH level, however, N-acetylcysteine (NAC), the GSH pro-drug, decreased the production of all three cytokines. Importantly, SAMe increased intracellular adenosine levels, and exogenous adenosine supplementation had effects similar to SAMe on TNF, IL-10 and IL-6 production. 3-Deaza-adenosine (DZA), a specific inhibitor of S-adenosylhomocysteine (SAH) hydrolase, blocked the elevation of IL-10 and IL-6 production induced by SAMe, which was rescued by the addition of exogenous adenosine. Furthermore, the enhancement of LPS-stimulated IL-10 and IL-6 production by both SAMe and adenosine was inhibited by ZM241385, a specific antagonist of the adenosine (A(2)) receptor. Our results suggest that increased adenosine levels with subsequent binding to the A(2) receptor account, at least in part, for SAMe modulation of IL-10 and IL-6, but not TNF production, from LPS stimulated monocytes.     

Chlorophylla biosynthetic routes and chlorophylla chemical heterogeneity in plants

A six-branched chlorophyll a biosynthetic pathway instead of a four-branched pathway has been proposed as being responsible for the formation of chlorophyll a in green plants. The several biosynthetic routes that make up the pathway have been described as leading to the formation of ten chemically different groups of chlorophyll a species. The latter differ from one another by one or more of the following modifications: (a) by having a vinyl or ethyl group at position 4 of the macrocycle, (b) by the nature of the long-chain fatty alcohols at position 7 of the macrocycle, and (c) by having a 6-membered lactone ring instead of a 5-membered cyclopentanone ring. The chemical structure of several of the metabolic intermediates of that pathway and of some of the chlorophyll a species have now been determined by primary chemical derivatization methods coupled to spectrofluorometric, nuclear magnetic resonance and mass spectral analyses. The formation of highly organized photosynthetic membranes in which some of the chlorophyll alpha molecules are specifically oriented is ascribed to the multiplicity of chlorophyll biosynthetic routes which result in the formation of multiple chlorophyll alpha chemical species. Proper orientation of chlorophyll in the photosynthetic membranes is visualized as being controlled by peripheral group modifications that either modulate the polarity of the Chl chromophore or control the magnitude of the net positive charge on the central Mg atom. Finally it is proposed that in addition to the proper orientation of chlorophyll a, chemical heterogeneity of the chlorophyll chromophores in the photosynthetic reaction centers is mandatory for efficient charge separation, and proper vectorial electron transfer.     

Abatement of microfibre pollution and detoxification of textile dye – Indigo by engineered plant enzymes

Microfibres (diameter <5 mm) and textile dyes released from textile industries are ubiquitous, cause environmental pollution, and harm aquatic flora, fauna, animals and human life. Therefore, enzymatic abatement of microfibre pollution and textile dye detoxification is essential. Microbial enzymes for such application present major challenges of scale and affordability to clean up large scale pollution. Therefore, enzymes required for the biodegradation of microfibres and indigo dye were expressed in transplastomic tobacco plants through chloroplast genetic engineering. Integration of laccase and lignin peroxidase genes into the tobacco chloroplast genomes and homoplasmy was confirmed by Southern blots. Decolorization (up to 86%) of samples containing indigo dye (100 mg/L) was obtained using cp-laccase (0.5% plant enzyme powder). Significant (8-fold) reduction in commercial microbial cellulase cocktail was achieved in pretreated cotton fibre hydrolysis by supplementing cost effective cellulases (endoglucanases, ß-glucosidases) and accessory enzymes (swollenin, xylanase, lipase) and ligninases (laccase lignin peroxidase) expressed in chloroplasts. Microfibre hydrolysis using cocktail of Cp-cellulases and Cp-accessory enzymes along with minimal dose (0.25% and 0.5%) of commercial cellulase blend (Ctec2) showed 88%–89% of sugar release from pretreated cotton and microfibres. Cp-ligninases, Cp-cellulases and Cp-accessory enzymes were stable in freeze dried leaves up to 15 and 36 months respectively at room temperature, when protected from light. Use of plant powder for decolorization or hydrolysis eliminated the need for preservatives, purification or concentration or cold chain. Evidently, abatement of microfibre pollution and textile dye detoxification using Cp-enzymes is a novel and cost-effective approach to prevent their environmental pollution.     

Is direct spectrophotometric determination of chlorophyll in pigment extracts of tissues under different physiological conditions valid?

Direct spectrophotometric determination of chlorophyll content from methanol extracts of young and senescent leaves of $\text{Thunbergia}\text{grandiflora}$ showed 29 and 16%, respectively, of mature leaves. Spectrophotometric estimation in the same extracts after separation of chlorophyll by thin layer chromatography or by direct fluorometric determination showed only 15 and 0.5% of mature leaves, indicating an error of 4 to 40 fold. In the above wide range of absorbance (0.5 to 100%) the lack of linearity between absorption and concentration resulted in additional error. Bound chlorophyll remaining in the pellet, not extractable by any solvent system, was also reported to vary depending on the physiological conditions of the tissue (Plant Physiol. 51, 660–666). Therefore, it is pointed out that the aforementioned errors observed in direct spectrophotometric determinations could be checked by monitoring simultaneously the cell or plastid suspensions $\text{in}\text{vivo}$ by fluorometry without any extraction.     

Interaction, functional relations and evolution of large and small subunits in Rubisco from prokaryota and eukaryota

In early biological evolution anoxygenic photosynthetic bacteria may have been established through the acquisition of ribulose bisphosphate carboxylase-oxygenase (Rubisco). The establishment of cyanobacteria may have followed and led to the production of atmospheric oxygen. It has been postulated that a unicellular cyanobacterium evolved to cyanelles which were evolutionary precursors of chloroplasts of both green and non-green algae. The latter probably diverged from ancestors of green algae as evidenced by the occurrence of large (L) and small (S) subunit genes for Rubisco in the chloroplast genome of the chromophytic algae Olisthodiscus luteus. In contrast, the gene for the S subunit was integrated into the nucleus in the evolution of green algae and higher plants. The evolutionary advantages of this integration are uncertain because the function of S subunits is unknown. Recently, two forms of Rubisco (L8 and L8S8) of almost equivalent carboxylase and oxygenase activity have been isolated from the photosynthetic bacterium Chromatium vinosum. This observation perpetuates the enigma of S subunit function. Current breakthroughs are imminent, however, in our understanding of the function of catalytic L subunits because of the application of deoxyoligonucleotide-directed mutagenesis. Especially interesting mutated Rubisco molecules may have either enhanced carboxylase activity or higher carboxylase:oxygenase ratios. Tests of expression, however, must await the insertion of modified genes into the nucleus and chloroplasts. Methodology to accomplish chloroplast transformation is as yet unavailable. Recently, we have obtained the first transformation of cyanobacteria by a colE1 plasmid. We regard this transformation as an appropriate model for chloroplast transformation.