Observations on tolerance to heavy metals of four green algae in relation to pH

Abstract

The inhibition of growth by different concentration of eight heavy metals: Cd, Cr, Co, Cu, Hg, Ni, Se and Tl, in inorganic medium at pH 3 and 6.5, was studied in four green algae: Chlorella protothecoides Krüger, Chlorella saccharophila (Krüger) Migula, Coenochloris sp. and Stichococcus bacillaris Naegeli.

The results suggest that pH has an important effect on heavy metal toxicity in algae although it is difficult to establish a relationship between pH and heavy metals.     

Uno studio citofotometrico delle proteine durante la mitosi nel meristema radicale di Allium cepa L.

Abstract

A cytophotometric study of proteins during mitosis in root tip meristematic cells of «Allium cepa L.». — Spectrophotometric analyses of the amount of Fast-green stainable proteins at different pH values (8,1; 6; 4; 2) have been accomplished in Allium cepa root tip meristematic cells during the four phases of mitosis. The results seem to indicate that: a) the highest absorption is detectable in correspondence of metaphase at each of the four pH values; b) the transition from prophase to metaphase is characterized by an increase of both proteins reacting at pH 8,1 (histones) and between pH 6 and pH 8,1 (neutral proteins); c) the transition from metaphase to anaphase is characterized by a loss of histones and of proteins reacting between pH 4 and pH 6 (acid proteins); d) the transition from anaphase to telophase is characterized by a loss of neutral proteins. The data are discussed in relation to the problem of chromosome coiling.     

Mechanism of the aromatic aminotransferase encoded by the Aro8 gene from Saccharomyces cerevisiae

The amino acid l-lysine is synthesized in Saccharomyces cerevisiae via the α-aminoadipate pathway. An as yet unidentified PLP-containing aminotransferase is thought to catalyze the formation of α-aminoadipate from α-ketoadipate in the l-lysine biosynthetic pathway that could be the yeast Aro8 gene product. A screen of several different amino acids and keto-acids showed that the enzyme uses l-tyrosine, l-phenylalanine, α-ketoadipate, and l-α-aminoadipate as substrates. The UV–visible spectrum of the aminotransferase exhibits maxima at 280 and 343 nm at pH 7.5. As the pH is decreased the peak at 343 nm (the unprotonated internal aldimine) disappears and two new peaks at 328 and 400 nm are observed representing the enolimine and ketoenamine tautomers of the protonated aldimine, respectively. Addition, at pH 7.1, of α-ketoadipate to free enzyme leads to disappearance of the absorbance at 343 nm and appearance of peaks at 328 and 424 nm. The V/E_t and V/K_{α-ketoadipate}E_t pH profiles are pH independent from pH 6.5 to 9.6, while the V/K_l-tyrosine pH-rate profile decreases below a single pK_a of 7.0 ± 0.1. Data suggest the active enzyme form is with the internal aldimine unprotonated. We conclude the enzyme should be categorized as a α-aminoadipate aminotransferase.     

不同pH值条件下硫酸盐还原菌组成及硫酸盐还原机制分析

【目的】从海洋沉积物中富集获得硫酸盐还原菌群,改变pH值进行培养,分析pH值对硫酸盐还原性质的影响,明确菌群组成和进行硫酸盐还原功能基因预测,探究硫酸盐还原机制。【方法】分析硫酸盐还原菌群在不同pH值条件下的硫酸盐还原率,在此基础上,利用高通量测序技术和PICRUSt软件分析硫酸盐还原菌群优势菌组成及硫酸盐还原相关基因相对丰度。【结果】硫酸盐还原菌群在不同pH值培养条件下的生长和硫酸盐还原率出现显著变化(P<0.01),在pH 5.0时达到峰值,分别为0.34±0.01和96.52%±0.44%。高通量测序数据显示,pH 5.0时菌群丰富度和多样性最高,优势菌属为假单胞菌(Pseudomonas)和芽孢杆菌(Bacillus),相对丰度较高的基因为同化性硫酸盐还原相关基因。【结论】硫酸盐还原菌富集生长的最适pH 5.0,在此条件下的高硫酸盐还原率由同化性硫酸盐还原途径主导,为揭示硫酸盐还原机制提供了实验支持,并拓宽了硫酸盐还原菌实践应用方面的种质资源。     

An anti-HBV anthraquinone from aciduric fungus Penicillium sp. OUCMDZ-4736 under low pH stress

To obtain new bioactive natural products, the effect of acidic stress on the metabolites of an aciduric fungus was investigated. This fungus, Penicillium sp. OUCMDZ-4736, which was isolated from the sediment around roots of mangrove (Acanthus ilicifolius), produced different compounds and higher yields under pH 2.5 than under neutral conditions. Using spectroscopic analyses and calculations, three new anthraquinone derivatives (1–3) were isolated and identified from the acidic fermentation broth (pH 2.5) of OUCMDZ-4736. Compound 1 showed much stronger anti-hepatitis B virus activity than that of the positive control, lamivudine, strongly inhibiting HBsAg and HBeAg secretion from HepG2.2.15 cells. These results show that extremophiles are a valuable resource of bioactive compounds, and that pH regulation is an effective strategy to induce metabolite production in aciduric fungi.

     

Presence of Bacillus coagulans spores and vegetative cells in rat intestine and feces and their physiological effects

ABSTRACT

This study was aimed to investigate the presence of Bacillus coagulans vegetative cells in the intestine and fecal samples in rats fed B. coagulans spores as well as to estimate the ratios of spores and vegetative cells in these samples. A two-step process has been developed to enumerate B. coagulans in different mixed bacterial samples, specifically (1) observation of yellow ring formation on modified GYEA medium upon incubation at 55°C, (2) microscopic examination of spore formation after 7 d of incubation. Our results have demonstrated the presence of vegetative cells in the intestinal and fecal samples in rats fed B. coagulans spores. The ratios of B. coagulans spores and vegetative cells in cecal fluid, colonic content, and feces were approximately 2:8, 2:8, and 4:6, respectively. The existence of B. coagulans vegetative cells improved the intestinal milieu through an elevated short-chain fatty acid concentrations, higher fecal moisture, and lower fecal pH.     

Aliphatic Amino Acid Side Chains Associate with the “Face” of the Adenine Ring

Abstract

We have synthesized the free amino acid adenylate anydrides of phenylalanine, leucine, isoleucine and valine. These activated compounds are very labile at high pH, but at low pH they become more stable. Proton NMR spectra of these adenylates show that, in every case, the hydrophobic side chains, even in these small molecules at low pH and low concentration, are associated with the “face” of the adenine ring. Although aromatic rings are known to associate with adenine in this fashion, to our knowledge this is the first report of an intercalative-type interaction of aliphatic side chains with nucleic acid bases. Since adenine is the most hydrophobic base, these interactions are of a hydrophobic character, and occur in spite of the fact that the adenine ring is protonated. These results may have implications regarding recognition processes in DNA-protein and RNA-protein interactions.     

Synthesis and Conformational Studies of O 5′, 6-Methanouridine—A New Type of Pyrimidine Cyclonucleoside

Abstract

The 5-oxo-6-methylene-pyrimidine-2,4-dione intermediate (6) that is formed when 5-acetoxy-6-acetoxymethyl-1-β-D-(5-O-acetyl-2,3-O-isopropylidene)-ribofuranosyluracil (5) is treated with sodium hydroxide undergoes cyclization at pH 14 to give 2′,3′-O-isopropylidene-5-hydroxy- O ⁵, 6-methanouridine (8) in good yield. Conversion of 8 into the 5-triflate ester 14 followed by reduction with [(Ph)₃P]₄Pd/Bu₃SnH and deblocking with acetic acid then affords O ^5′, 6-methanouridine (4) Conformational studies (NOE difference spectra, vicinal ¹H-¹³C coupling constants, NOESY and CD spectra, molecular modeling) indicate that the C7-methylene group of 4 projects towards the furanose ring oxygen atom, producing a glycosyl rotation angle of about ? 160°.     

TOXIN EXTRACTION FROM THE BLUE-GREEN ALGA MICROCYSTIS AERUGINOSA BY DIFFERENT EXTRACTION MEDIA

SUMMARY

The extractability of toxin from Microcystis aeruginosa isolate UV-006 by different extraction media such as O, 1N HC1, 2N CH₃COOH, Triton X-100 and water at different pH levels was investigated. The best recovery of toxin was achieved with water at a pH of 10 while the recoveries with the more acidic media tended to be lower.     

L'evoluzione della cerchia legnosa in Arbutus Andrachnoides Link. in Firenze,dal luglio 1946 al Giugno 1947

Summary

The evolution of the wood ring in arbutus andrachnoides link, in florence (from July 1946 to June 1947).

The anatomical characters of the wood ring of the stem and of the young branch of Arbutus andrachnoides Link have been studied in Florence.

The results are the following: the cambial tissue in the stem starts dividing at the end of April and continues during the summer months, ending completely in September.

In the branch the cambium differentiates almost a month earlier, namely at the beginning of April.

In both cases the only wood ring produced is completed at the end of September. Comparing the evolution of this wood with the climatic factors it can be seen that the cambium activity starts in a period of remarkable rainfall and of regular increase of temperature and presents a remarkable activity still at the end of August.

Arbutus andrachnoides Link. is a spontaneous hybrid between A. Unedo and A. Andrachne and its distribution (in Greece and in the gréek islands) shows that A. Unedo and A. Andrachne had the possibility to overlap in this area and to produce this hybrid.     

Genetic adaptation to soil acidification: experimental evidence from four grass species

Anthropogenic acidification has reduced soil pH and released potentially toxic aluminium (Al) ions in many regions. This investigation examines whether increased acidity has caused genetic adaptation to acidic conditions within the grass species Elymus caninus, Poa nemoralis, Deschampsia cespitosa and D. flexuosa. We sampled tussocks (genets) of each species in two regions of southern Sweden, differing in their exposure to acidifying deposition. The tolerance of the genets was tested in a solution experiment with different pH and Al concentrations. Our data suggest that species found at lower pH field locations have a greater tolerance to low pH and high Al levels than species found on less acidic soils. Analysis of variance showed a significant average effect of population and (or) genet in most species; however, we found little evidence of genetic adaptation to acidic conditions at the regional, population and micro-site level. In fact, there was no consistent change in the ranking of populations or genets with varying pH or Al concentration. Based on these results, we hypothesize that phenotypic plasticity rather than genetic adaptation has been favoured as the predominant mechanism to cope with soil acidity in the four grass species.     

以pH为扰动因子探究电化学厌氧消化产甲烷代谢通量与微生物的关系

【背景】电化学厌氧消化(electrochemical anaerobic digestion,EAD)系统的代谢途径由具备不同功能的微生物所主导,其代谢通量与功能微生物丰度、活性及群落结构相关。【目的】探究EAD产甲烷代谢通量与微生物的关系。【方法】采用代谢通量分析(metabolic flux analysis,MFA)方法,以pH为扰动因子得到微生物群落与产甲烷通量的响应关系。【结果】pH 7.5扰动时产甲烷通量最大为0.398 4±0.029 3,较对照组(pH 6.9)的0.297 4±0.012 7和扰动组(pH 6.3)的0.136 5±0.012 0分别提高了25%和65%。另外,平均有33.8%±3.1%的氢气(通量)用于还原二氧化碳产甲烷和乙酸,平均有21.0%±2.6%的乙酸(通量)转化为甲烷。此外,产甲烷通量与Mariniphaga、Methanosaeta和Desulfomicrobium的丰度呈正相关,与Sedimentibacter的丰度呈负相关且影响显著。【结论】在EAD产甲烷体系中产甲烷菌和产酸菌共存时,pH值略大于7.0的环境有利于甲烷的生成,改变E...     

甘肃白银铜矿矿坑土壤细菌和古菌的多样性及坡度分布特征

【背景】甘肃白银铜矿作为西部地区的重要矿区，探究其细菌和古菌多样性及坡度分布特征对明确矿区微生物多样性分布具有关键意义。【目的】通过分析白银铜矿矿坑不同坡度的土壤细菌群落多样性和古菌群落多样性，探究不同坡度土壤样品细菌及古菌多样性与理化性质之间的关系。【方法】以不同坡度的白银铜矿土样为材料，采用Illumina HiSeq测序技术，分析样品的细菌多样性和古菌多样性。【结果】α和β多样性分析表明，ACE、Chao1、Shannon和Simpson等多样性指数在样品间存在显著差异。白银铜矿矿坑土壤的细菌排名前十的纲是Gammaproteobacteria、Oxyphotobacteria、Alphaproteobacteria、Bacteroidia、Actinobacteria、Clostridia、Nitrospira、Bacilli、Mollicutes和Acidimicrobiia，相对丰度最高的是Gammaproteobacteria。在纲水平上，白银铜矿的古菌由Thermoplasmata、Nitrososphaeria、Methanomicrobia、Halobacteria、Methanobacteria、Group_1.1c和Bathyarchaeia组成，相对丰度最高的是Thermoplasmata。冗余分析(redundancy analysis,RDA)得出，pH和速效磷是影响土壤多样性的最重要因素。【结论】白银铜矿为强酸性铜矿，其土壤铜离子含量最高。从坡顶到坡底，pH呈现先降低再升高的趋势(2.18-4.75)，铜离子(20-150mg/kg)和总铁(2.5-50mg/kg)呈现先升高后降低的趋势，铵态氮(3.61-44.90mg/kg)、速效磷(0-56.79mg/kg)和速效钾(9.07-35.65mg/kg)含量低且呈现波动趋势，硫化物(1mg/kg)无明显变化。白银铜矿矿坑土壤细菌相对丰度最高的属为Acidithiobacillus，古菌相对丰度较高的属为uncultured_bacterium_f_Ferroplasmaceae和uncultured_bacterium_f_Nitrososphaeraceae。其中，细菌多样性受到pH驱动，古菌多样性受到速效磷的驱动。本研究有助于我们进一步了解白银铜矿土壤微生物群落的变化。     

pH influence on the consumption of limonin species by Rhodococcus fascians cells

Summary The ability of Rhodococcus fascians cells to degrade limonin and limonin species (limonoate, limonoate-D-ring lactone and limonoate-A-ring lactone) was checked against pH. These studies showed a marked effect of pH on cell growth mainly due to substrate availability (limonin species). Evolution of limonin and its species within the medium were followed at different pH values. The best substrate for Rhodococcus fascians at pH 7.0 was limonoate whereas at pH 4.0 to 5.5 it appeared to be limonin. Results suggest that the citrus juice debittering process start only once the natural precursor of limonin (limonoate A ring lactone) has been transformed into limonin, the equilibrium displacement being governed by the citrus juice pH.     

The c‐ring ion binding site of the ATP synthase from Bacillus pseudofirmus OF4 is adapted to alkaliphilic lifestyle

In the c‐ring rotor of ATP synthases ions are shuttled across the membrane during ATP synthesis by a unique rotary mechanism. We investigated characteristics of the c‐ring from the alkaliphile Bacillus pseudofirmus OF4 with respect to evolutionary adaptations to operate with protons at high environmental pH. The X‐ray structures of the wild‐type c₁₃ ring at pH 9.0 and a ‘neutralophile‐like’ mutant (P51A) at pH 4.4, at 2.4 and 2.8 Å resolution, respectively, reveal a dependency of the conformation and protonation state of the proton‐binding glutamate (E⁵⁴) on environmental hydrophobicity. Faster labelling kinetics with the inhibitor dicyclohexylcarbodiimide (DCCD) demonstrate a greater flexibility of E⁵⁴ in the mutant due to reduced water occupancy within the H⁺ binding site. A second ‘neutralophile‐like’ mutant (V21N) shows reduced growth at high pH, which is explained by restricted conformational freedom of the mutant's E⁵⁴ carboxylate. The study directly connects subtle structural adaptations of the c‐ring ion binding site to in vivo effects of alkaliphile cell physiology.     

Design,synthesis, spectral analysis and in vitro microbiological evaluation of 2-phenyl-3-(4,6-diarylpyrimidin-2-yl)thiazolidin-4-ones

A series of novel 2-phenyl-3-(4,6-diarylpyrimidin-2-yl)thiazolidin-4-ones 23-33 were synthesized, and studied for their in vitro antibacterial and antifungal activities against clinically isolated strains. Generally compounds possessing electron donating groups showed good antibacterial activity. Compound 31, which contain both electron withdrawing chloro and electron donating methyl groups showed potent activity against all the tested Gram positive and Gram negative bacterial strains whereas compounds 32 and 33 which contain electron donating methoxy functional group at the para position of the phenyl ring attached to pyrimidine ring showed promising activity against S.aureus, S.typhii and E.coli. Compounds 32 and 33, both containing electron withdrawing groups (-Cl, -F) showed excellent activities against all the tested A. flavus, Mucor, Rhizopus and M.gypsuem fungal strains. while against Mucor, compound 27 which contains an electron donating methyl group at the para position of the phenyl ring attached to pyrimidine ring showed promising activity. Also compound 31, which contains both electron withdrawing chloro and electron donating methyl groups showed potent activity against A. flavus and Rhizopus.     

Synthesis of mixed N,N′-(Ar,Ar′-diaryl)iminoisoindolines for applications in palladacycle formations

The synthesis of N,N′-(Ar,Ar′-diaryl)iminoisoindolines containing different aryl groups bound to the two nitrogen atoms is described. The iminoisoindolines were obtained by a three component, one-pot reaction of phthalaldehyde with 1 equivalent p-NO₂-aniline and 1 equivalent p-R-aniline, where R = H, Me, MeO or ⁱPr, resulting in formation of non-symmetrically substituted (mixed) iminoisoindolines, 1-p-nitrophenylimino-2-p-R-phenylisoindoline (R = H (1), Me (2), MeO (3), and ⁱPr (4)), as analytically pure precipitates requiring no further purification. Only one isomer precipitates from solution wherein the nitro group resides exclusively at the imine position while the more electron donating substituent ends up on the isoindoline ring position. Further reaction with Pd(OAc)₂ in dichloromethane at room temperature results in formation of six-membered [C,N] dinuclear cyclopalladated complexes with the general formula [(Ar,Ar′-diaryliminoisoindoline)Pd{μ-OAc}]₂.     

酸胁迫下琥珀酸放线杆菌的生理及转录应答

【目的】通过琥珀酸放线杆菌Actinobacillus succinogenes CGMCC1593对酸胁迫的生理应答和转录组学分析,探究琥珀酸放线杆菌酸胁迫的机制。【方法】测定不同pH对细胞生长、H+-ATPase、细胞内pH的影响;测定酸胁迫前后细胞膜和谷氨酸脱氢酶的变化、谷氨酸对琥珀酸放线杆菌生长的影响;通过RNA-seq测序分析酸胁迫条件下的差异表达基因。【结果】随pH值的降低,细胞生长受抑制,H+-ATPase的活性下降。pH 4.7酸胁迫后,细胞膜受到严重损伤,谷氨酸对酸胁迫后的细胞有保护作用,GDH酶活响应酸胁迫后略有增加。酸胁迫后,39个基因差异表达较为显著,其中49%基因属于应激蛋白、转运蛋白,小部分基因与代谢相关。【结论】本文探究了琥珀酸放线杆菌酸胁迫下的生理及转录应答,研究结果可为寻找增强琥珀酸放线杆菌耐酸性策略提供参考。     

The role of regulation of cell speed in the behavior of Physarum polycephalum amoebae

Studies on the behavior of wild-type and mutant Physarum polycephalum amoebae have revealed that regulation of cell speed results in different patterns of cell dispersion in different environments and have shown that P. polycephalum can be used for genetic studies of the mechanisms responsible for this element of cell behavior. Colonies generated by clonal populations of amoebae growing on E. coli display alternate colony morphologies depending on the pH of the culture medium and the presence of live E. coli as a nutrient. In the larger ‘spreading colonies’ cells at the outside of a colony are dispersed over a wide band of bacteria while in the smaller ‘aggregate ring colonies’ most cells moving on bacteria are aggregated in a regularly shaped ring on a narrow band of bacteria at the border of the bacterial lawn created when amoebae completely consume the bacteria available in the colony center. Measurements of cell growth, the rate of colony expansion, and the rate of single cell movement show that cells in contact with bacteria move more slowly in aggregate ring than in spreading colonies. Moreover, since in aggregate ring colonies the rate of movement of cells in contact with bacteria is also reduced relative to that of cells moving on adjacent regions of the agar surface, inhibition of cell speed appears to be at least partially responsible for generating the aggregate ring morphology. Characterization of the behavior of a single locus mutant which generates spreading colonies under conditions where aggregate ring colonies are normally formed has provided additional evidence that a specific mechanism is involved in controlling the distribution of amoebae through regulation of cell speed. Furthermore, the studies of this mutant have shown that aberrant colony morphology can be used as an easily recognized phenotype for identifying and studying mutants with defects which affect the regulation of cell speed.     

The oxidation state of active site thiols determines activity of saccharopine dehydrogenase at low pH

Saccharopine dehydrogenase catalyzes the NAD-dependent conversion of saccharopine to generate l-lysine and α-ketoglutarate. A disulfide bond between cysteine 205 and cysteine 249, in the vicinity of the dinucleotide-binding site, is observed in structures of the apoenzyme, while a dithiol is observed in a structure with AMP bound, suggesting preferential binding of the dinucleotide to reduced enzyme. Mutation of C205 to S gave increased values of V/E_t and V/KE_t at pH 7 compared to wild type. Primary deuterium and solvent deuterium kinetic isotope effects suggest the catalytic pathway, which includes the hydride transfer and hydrolysis steps, contributes more to rate limitation in C205S, but the rates of the two steps relative to one another remain the same. There is a large increase in the rate constants V₁/E_t and V₁/K_NADEt at pH values below 7 compared to WT. Data indicate the low pH increase in activity results from a decreased sensitivity of the C205S mutant enzyme to the protonation state of an enzyme group with a pK_a of about 7, likely responsible for a pH-dependent conformational change. Reduction of WT and C205S mutant enzymes with TCEP gives equal activities at pH 6, consistent with the increased activity observed for the C205S mutant enzyme.