Effects of UV-B on motility and photoorientation in the cyanobacterium,Phormidium uncinatum

UV-B irradiation has a detrimental effect on the survival of populations of the filamentous cyanobacterium, Phormidium uncinatum, at levels slightly higher than those currently measured at the surface of the earth. The organisms are not damaged or killed by UV-B radiation at 300 nm of 200 Wm^-2 for up to 20 h; but slightly increased levels of UV-B irradiation (2 h of 200 Wm^-2 at 300 nm) drastically impair motility, phototactic orientation and photophobic responses. These photosynthetic organisms require a narrow light intensity range for growth so that any decrease in their ability to actively search for and move into areas of favorable light conditions is bound to affect the survival of a population. The fluorescence yield of both phycobilins and chlorophyll is not altered even after 20 h of UV-B irradiation (200 Wm^-2 at 270 nm) indicating that UV-B at that dose does not affect the photosynthetic apparatus. The organisms are killed either by too bright intensities which bleach the photosynthetic pigments or by the lack of energy when they are unable to avoid moving into dark areas.     

昆虫趋光性及其机理的研究进展

依据目前已有资料 ,从行为学、生理学及田间应用调查等方面概述了近几十年昆虫趋光性的国内外研究进展。其中 ,行为学与生理学研究较多 ,且两者结果基本一致 ,相互补充 ,为趋光性机制的假说提供了可靠的依据。关于昆虫趋光性机制的假说较多 ,其中报道较多的是光干扰假说、光定向行为假说和生物天线假说 3种 ,现在较为普遍接受的是前两者。光干扰假说是指刺眼作用干扰昆虫的正常活动导致趋光 ,而光定向行为假说则指昆虫趋光是由于光定向行为所致     

Evidence for photosynthetic independence of viral multiplication in cyanophage LPP-1 infected cyanobacterium Phormidium uncinatum

Abstract Pigment decomposition, oxygen evolution and CO₂ fixation were measured in the cyanobacterium Phormidium uncinatum after infection with cyanophage LPP-1, under light and dark conditions. A gradual decrease in para benzoquinone supported O₂ evolution, chlorophyll a and phycocyanin level were noticed after 6 h of infection. These results demonstrated decreased photosynthetic activity of the host P. uncinatum prior to the start of LPP-1 multiplication. Metabolic inhibitor investigations confirmed that the cyanophage LPP-1 multiplication was independent of host photosynthesis.     

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.     

昆虫趋光性研究的回顾

利用昆虫的趋光性开展农林卫生害虫诱杀,一直是害虫绿色防控的组成部分。本文综述了昆虫的多种趋光性行为,昆虫趋光性机制—罗盘理论、马赫带效应理论和开放空间理论,对在物理、生物环境条件、光和光源属性条件下昆虫趋光的生态适应性,以及对昆虫抵达光源的位置和移动轨迹进行了讨论。     

Interrelationship between hydrogen peroxide,ammonia, glutamine,hydroxylamine and nitrite metabolism in the cyanobacterium Phormidium uncinatum

On transition from nitrogen starvation to ammonia or ammonia/glutamine sufficiency Phormidium uncinatum produces high amounts of H₂O₂, which is consumed by several oxidative reactions catalyzed by thylakoid membrane bound enzymes. These include: oxidation of glutamine to free hydroxylamine, of ammonia to nitrite, of bound hydroxylamine to nitrite, and dismutation of free hydroxylamine to ammonia and nitrite. A possible role of these transformations for detoxification is discussed.Non-standard abbreviations FCCP p-trifluormethoxy carbonylcyanide phenylhydrazone - DCMU dichloromethyl urea     

Characterization of the Eyespot Regions of "Blind"Chlamydomonas Mutants after Restoration of Photophobic Responses

Chlamydomonas reinhardtii exhibits photophobic and positive and negative phototactic responses that can be defined for cell populations using computerized cell tracking and motion analysis. Mutants CC-2359 and FN68 are pigment deficient mutants that are blocked in carotenoid synthesis and lack these photo responses. In particular, neither mutant exhibits flash-induced photophobic responses to visible light stimuli to which wild-type gametic cells exhibit a strong response, with several behavioral stages. Upon addition of all-trans retinal to these mutants, the photophobic responses are restored with minor quantitative differences from wild-type populations. Using both light and electron microscopy, we have compared the ultrastructural characteristics of wild-type C. reinhardtii to those of both mutants. As previously described, wild-type cells contain an eyespot consisting of 2–4 layers of pigmented granules encased within thylakoid membranes, located between the distal extremities of the flagellar root. This structure is also visible as an orange-red spot in light microscopy. The photoreceptor is thought to be concentrated in the plasma membrane above the eyespot. The mutant, CC-2359, lacks this eyespot as seen by both light and electron microscopy, even when the photophobic response has been restored. FN68-like mutants studied earlier by Morel-Laurens and Feinlieb and others contain an eyespot which can be seen only by electron microscopy. In FN-68, the eyespot generally has the same dimensions as in wt cells, differing mainly in pigment granule appearance. Consistent with these findings, several laboratories have shown that the full range of phototactic responses can be reconstituted in FN68 and CC-2359, but that negative phototaxis requires a significantly stronger light stimulus in the latter strain. We confirm the suggestion that the eyespot is not necessary for the photophobic response, and is not critical for the appropriate assembly and function of the photophobic response receptor in the membrane. Furthermore, the locus of reconstitution of the functional receptor is not the eyespot. Because of the definitive demonstration of the absence of the eyespot in CC-2359, however, the eyespot may play a role in negative phototaxis.     

Dismutation of hydroxylamine to ammonia and nitrite by a novel, membrane-bound enzyme from the cyanobacterium Phormidium uncinatum

Extracts from ammonium-grown phototrophic cultures of Phormidium uncinatum exhibited a catalytic and stoichiometric formation of nitrite and ammonia from hydrogen peroxide and hydroxylamine. This reaction was due to a novel enzyme (referred to as hydroxylamine dismutase), which was bound to the heavier thylakoid membranes. The enzyme was solubilized from the membranes by detergent treatment and further purified by ion-exchange chromatography. On the basis of inhibitor studies, the involvement of metal ions and sulfhydryl groups in the characteristic reaction is suggested.     

Gated ion fluxes involved in photophobic responses of the blue-green alga,Phormidium uncinatum

The sensory transduction chain of photophobic responses in the blue-green alga, Phormidium uncinatum seems to involve a gating cation transport through membrane bound ion channels which provides an effective amplification.The calcium conducting ionophore A23187 inhibits the photophobic response totally and induces frequent reversals which resemble phobic responses but occur without any light stimulation. This indicates that the electrogenic ion conductance may depend on a gradient of divalent cations, esp. calcium. The calcium conductance during a photophobic response is further confirmed by the inhibitory effect of ruthenium red and lanthanum, blockers of the electrogenic calcium transport. In the case of lanthanum this inhibition is found at a concentration at which neither the number of motile filaments nor the average speed of movement is impaired.Incorporation of ionophores for monovalent cations (gramicidin and valinomycin) only partially impairs the response. Similarly, inhibition of the Na⁺/K⁺ pump by ouabain is less effective. Thus, the existence of a countercurrent of monovalent cations during the response, which has been described for e.g. ciliates, is yet obscure in blue-green algae.     

Regulation of nitrate reduction in a cyanobacterium Phormidium uncinatum: Distinctive modes of ammonium-repression of nitrate and nitrite reductases

Abstract A 5.8 kbp DNA fragment from Clostridium cellulovorans (ATCC 35296) containing endo-β-1,4-glucanase (1,4-β- d -glucan glucanohydrolase, carboxymethylcellulase, CMCase; EC 3.2.1.4) gene, engD was cloned in Escherichia coli . The clone harboring a subcloned 3.8 kb fragment in plasmid, pEQ52V, produced an enzyme that showed both endo-β-1,4-glucanase activity as well as cellobiosidase activity. Zymograms with the engD encoded enzyme with carboxymethyl-cellulose as the substrate indicated that the molecular mass of the active protein was 50 000.     

Temperature Effect on the Photo-Accumulation and Phobic Response of Volvox aureus*

SYNOPSIS. The effect of temperature on photoaccumulation and photophobic response of Volvox aureus were studied. The algae exhibited positive photoaccumulation at room temperature and negative at low temperature. When stimulated with light of intermediate intensiy (～ 5 × 10³ lux), the phobic response of the algae consisted of a decrease in the frequency or the cessation of flagellar movement in the anterior cells. At room temperature, an increase in light intensity elicited the phobic response, whereas at low temperature a decrease in light intensity was the effective stimulus. The phobic response lasted only a few seconds. The positive and negative photoaccumulations of the algae could be explained by the brief cessation of flagellar movement in the anterior cells, elicited by an increase of stimulus light at room temperature or a decrease of stimulus at low temperature.     

Dependence of the photophobic response of the blue-green alga,Phormidium uncinatum,on cations

It is suggested that photophobic responses caused by a sudden step-down in light intensity require the presence of cations in the blue-green alga, Phormidium uncinatum.Drastic removal of cations abolishes the phobic response, which recovers after addition of Ca²⁺ ions. Calcium can be substituted for partially by other cations with an effectivity following the sequence Ca>Mg>Na>Ba>Co=0. During the photophobic response there is a 25% increase in ⁴⁵Ca binding by the cells related to a step-down in light intensity. Three seconds after a light-dark transition there is a sharp increase in the binding of labelled calcium, followed by a subsequent release.Flushing the filaments with high cation concentrations, esp. calcium causes a reversal of movement in the absence of a light stimulus similar to a photophobic reversal. This stimulus could trigger the same sequence of events in the transduction chain bypassing the primary photoresponse.Abbreviations EDTA Ethylene diaminetetraacetic acid - EGTA ethylene glycol-bis (2-aminoethylether) N,N tetraacetic acid     

昆虫趋光行为的光胁迫假说

趋光性是昆虫的固有行为特征之一,被广泛的应用在害虫物理防治中。本文综述了几种主流的昆虫趋光性假说,着重介绍了昆虫在趋光过程中的行为反应、受光胁迫后生理应激和补偿效应,提出了昆虫趋光行为的光胁迫假说,以期为昆虫趋光性理论研究提供新的思路。     

Contributions of Theodor Wilhelm Engelmann on phototaxis,chemotaxis, and photosynthesis

Theodor Wilhelm Engelmann (1843–1909), who had a creative life in music, muscle physiology, and microbiology, developed a sensitive method for tracing the photosynthetic oxygen production of unicellular plants by means of bacterial aerotaxis (chemotaxis). He discovered the absorption spectrum of bacteriopurpurin (bacteriochlorophyll a) and the scotophobic response, photokinesis, and photosynthesis of purple bacteria.     

Spectrophotometric measurement of plastoquinone photoreduction in the blue-green alga,Phormidium uncinatum

The redox state of plastoquinone was measured in vivo in the blue-green alga, Phormidium uncinatum by means of a double beam UV-spectrophotometer. The difference in absorbance of the oxidized and the reduced forms of plastoquinone was amplified, and stored and averaged in a computer. The redox state was changed by two alternating actinic light beams. When one actinic wavelength was kept constant at 700 nm (PSI) variation of the other yielded an action spectrum representing photosystem II. The inhibitors of the photosynthetic electron transport chain, DCMU and DBMIB, reduced the difference in absorbance between the oxidized and reduced forms of plastoquinone.Abbreviations DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - DCMU 3-(3,4-dichlorophenyl)-1, 1-dimethylurea     

Electrical and proton gradients in the sensory transduction of photophobic responses in the blue-green alga,Phormidium uncinatum

The gliding filaments of the blue-green alga Phormidium uncinatum stop their movement almost instantaneously when transfered from their growth pH of 7.2 into a buffer 4.5 or 12.5. A pH jump into the range between 5.6 and 12.0 induces no visible response while in the range between 4.9 and 5.5 the organisms reverse the direction of their movement. The pH jump is believed to simulate an early step during the sensory transduction chain of the photophobic response which eventually results in a reversal of movement.One of the subsequent steps is the inversion of an electric potential gradient existing between the front and rear ends of a filament which dictates the direction of movement. A similar reversal of the naturally existing potential gradient can be provoked by switching on an external do field when the filaments move towards the anode or switching it off when the filaments glide in the opposite direction. Implications of these results on the current model of sensory transduction of the photophobic response in Phormidium uncinatum are being discussed.     

Regulation of nitrate assimilation in the cyanobacterium Phormidium laminosum

The intracellular ratio of 2-oxoglutarate to glutamine has been analyzed under nutritional conditions leading to different activity levels of nitrate-assimilating enzymes in Phormidium laminosum (Agardh) Gom. This non-N₂-fixing cyanobacterium adapted to the available nitrogen source by modifying its nitrate reductase (NR; EC 1.7.7.2), nitrite reductase (NiR; EC 1.7.7.1) and glutamine synthetase (GS; EC 6.3.1.2) activities. The 2-oxoglutarate/glutamine ratio was similar in cells adapted to grow with nitrate or ammonium. However, metabolic conditions that increased this ratio [i.e., nitrogen starvation or l-methionine-d,l-sulfoximine (MSX) treatment] corresponded to high activity levels of NR, NiR, GS (except in MSX-treated cells) and glutamate synthase (GOGAT; EC 1.4.7.1). By contrast, metabolic conditions that diminished this ratio (i.e., addition of ammonium to nitrate-growing cells or addition of nitrate or ammonium to nitrogen-starved cells) resulted in low activity levels. The variation in the 2-oxoglutarate/glutamine ratio preceded the changes in enzyme activities. These results suggest that changes in the 2-oxoglutarate/glutamine ratio could be the signal that triggers the adaptation of P. laminosum cells to variations in the available nitrogen source, as occurs in enterobacteria.Abbreviations Chl chlorophyll - GOGAT ferredoxin-dependent glutamate synthase (EC 1.4.7.1) - GS glutamine synthetase (EC 6.3.1.2) - MSX l-methionine-d,l-sulfoximine - NiR nitrite reductase (EC 1.7.7.1) - NR nitrate reductase (EC 1.7.7.2) - TP total protein This work has been partially supported by grants from the Spanish Ministry of Education and Science (DGICYT PB88-0300 and PB92-0464) and the University of the Basque Country (042.310-EC203/94). M.I.T. was the recipient of a fellowship from the Basque Government.     

Generation of lysoglyceroglycolipids in the cyanobacterium, Phormidium tenue.

Two kinds of lysoglycolipids, monogalactosyl 1-monoacylglycerol and digalactosyl 1-monoacylglycerol were generated in the cyanobacterium, Phormidium tenue, when it was stored at -20 degrees for more than 1 month. By comparison of the compositions of fatty acid residues between monogalactosyl 1-monoacylglycerol and monogalactosyl diacylglycerol, digalactosyl 1-monoacylglycerol and digalactosyl diacylglycerol, respectively, the 1-monoacylgalactolipids were presumed to be formed by regioselective deacylation at the sn-1 position with subsequent acyl-group migration from the sn-2 to the sn-1 position. In contrast, 1-monoacyl derivatives of sulphoquinovosyl diacylglycerol and phosphatidylglycerol, the other membrane lipids contained in cyanobacteria, were not formed.