Extensibility of isolated cell walls in the giant tip-growing cells of the xanthophycean alga Vaucheria terrestris

Apical cell wall fragments isolated from the giant-cellular xanthophycean alga Vaucheria terrestris sensu Götz were inflated with silicone oil by applying internal pressure ranging from 0.1 to 0.7 MPa, and the time-course of cell wall deformation was recorded and analyzed by videomicroscopy. Cell wall extensibility in the tip-growing region was estimated by the pressure required for cell wall extension, the amount of total extension until cell wall rupture and the rate of cell wall extension. Apical cell walls exhibited gradual extension, or creep, during inflation, which was eventually followed by rupture at the apical portion, whereas no appreciable extension was found in the cylindrical basal portion of the cell wall fragment. Besides the largest extension observed around the tip, substantial extension was also observed along the subapical region of the cell wall. The wall extensibility was dependent on the buffer pH used for infiltration before inflation. The optimum pH for the extension was about 8.0, but the cell wall was much less extensible after infiltration with an acidic buffer. Cell wall extensibility was dependent on the pH of the buffer used before inflation, regardless of that used in the previous infiltration. Moreover, pretreatment of the cell wall with a protease caused considerable loosening of cell walls, but affected the pH dependence of cell wall extensibility little. These results indicate that the extensibility of the cell walls in the giant tip-growing cells of the alga is distinct from that of plant cells that exhibit "acid growth" in its dependence on environmental pH and the role of cell wall proteins.     

Two endogenous proteins that induce cell wall extension in plants.

Plant cell enlargement is regulated by wall relaxation and yielding, which is thought to be catalyzed by elusive "wall-loosening" enzymes. By employing a reconstitution approach, we found that a crude protein extract from the cell walls of growing cucumber seedlings possessed the ability to induce the extension of isolated cell walls. This activity was restricted to the growing region of the stem and could induce the extension of isolated cell walls from various dicot stems and the leaves of amaryllidaceous monocots, but was less effective on grass coleoptile walls. Endogenous and reconstituted wall extension activities showed similar sensitivities to pH, metal ions, thiol reducing agents, proteases, and boiling in methanol or water. Sequential HPLC fractionation of the active wall extract revealed two proteins with molecular masses of 29 and 30 kD associated with the activity. Each protein, by itself, could induce wall extension without detectable hydrolytic breakdown of the wall. These proteins appear to mediate "acid growth" responses of isolated walls and may catalyze plant cell wall extension by a novel biochemical mechanism.     

Calcium and the mechanical properties of soybean hypocotyl cell walls: Possible role of calcium and protons in cell-wall loosening

The role of calcium in the mechanical strength of isolated cell walls of soybean (Glycine max (L.) Merr. cv. Wayne) hypocotyls has been investigated, using the Instron technique to measure the plastic extensibility (PEx) of methanol-boiled, bisected hypocotyl sections and epidermal strips, and atomic absorption spectroscopy to measure wall calcium. Plastic extensibility was closely correlated with the growth rate of intact soybean hypocotyls. Removal of calcium from isolated cell walls by ethylene glycol-bis(2-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA) or low pH increased PEx, while addition of calcium decreased PEx; both effects were reversible. The amount of calcium removed and the increase in PEx at pH 4.5 were strongly dependent upon the chelating ability of the buffer anion. There was a direct correlation between the amount of calcium removed from the wall by EGTA or acid and the increase in PEx. Removal of up to 60% of the calcium increased PEx of half-section up to two fold, but further loss of calcium caused a much greater increase in PEx. With epidermal strips, PEx increased only when calcium was reduced below a threshold. At pH 3.5, there was an additional increase in PEx after a lag of about 2 h; this additional increase may be the result of acid-induced cleavage of a different set of load-bearing bonds. We conclude that calcium bridges are part of the load-bearing bonds in soybean hypocotyl cell walls, and that breakage of these crosslinks by apoplastic acid participates in wall loosening. Acid-induced solubilization of wall calcium may be one mechanism involved in wall loosening of dicotyledonous stems.Abbreviations EGTA ethylene glycol-bis(2-aminoethyl ether)-N,N,N,N-tetraacetic acid - PEx Instron plastic extensibility     

An extrinsic marker for higher plant cell walls

Summary Cytochromec was ionically bound to cell walls as a useful extrinsic marker. The marker binds rapidly, can readily be removed by salt treatment, and can be quantitated by conventional spectrophotometric procedures. The use of the marker allows each step of a cell wall purification to be monitored qualitatively and, furthermore, it provides a rapid, simple quantitative method to determine the yield of purified cell walls once isolated from the cell.Abbreviations pI Isoelectric pH - EDTA Ethylenediaminetetra-acetic acid - kD kiloDaltons - Cytc Cytochrome c - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - MES 2(N-Morpholino)ethanesulfonic acid     

Involvement of an N-Acetylglucosaminidase in Autolysis of Propionibacterium freudenreichii CNRZ 725

Propionibacterium freudenreichii plays an important role in Swiss cheese ripening (it produces propionic acid, acetic acid, and CO₂). Moreover, autolysis of this organism certainly contributes to proteolysis and lipolysis of the curd because intracellular enzymes are released. By varying external factors, we determined the following conditions which promoted autolysis of both whole cells and isolated cell walls of P. freudenreichii CNRZ 725: (i) 0.1 M potassium phosphate buffer (pH 5.8) at 40°C and (ii) 0.05 to 0.1 M KCl at 40°C. We found that early-exponential-phase cells possessed the highest autolytic activity. It should be emphasized that the pH of Swiss cheese curd (pH 5.5 to 5.7) is near the optimal pH which we determined. Ultrastructural observations by electron microscopy revealed a 16-nm-thick homogeneous cell wall, as well as degradation of the cell wall that occurred concomitantly with cell autolysis. In the presence of 0.05 M potassium chloride, there was a great deal of isolated cell wall autolysis (the optical density at 650 nm decreased 77.5% ± 7.3% in 3 h), and one-half of the peptidoglycan material was released. Finally, the main autolytic activity was due to an N-acetylglucosaminidase activity.     

Cell wall degradation ofStaphylococcus aureus by lysozyme

In contrast to former findings lysozyme was able to attack the cell walls ofStaphylococcus aureus under acid conditions. However, experiments with¹⁴C-labelled cell walls and ribonuclease indicated that, under these conditions, lysozyme acted less as an muralytic enzyme but more as an activator of pre-existing autolytic wall enzymes. Electron microscopic studies showed that under these acid conditions the cell walls were degraded by a new mechanism (i.e. attack from the inside). This attack on the cell wall started asymmetrically within the region of the cross wall and induced the formation of periodically arranged lytic sites between the cytoplasmic membrane and the cell wall proper. Subsequently, a gap between the cell wall and the cytoplasmic membrane resulted and large cell wall segments became detached and suspended in the medium. The sequence of lytic events corresponded to processes known to take place during wall regeneration and wall formation. In the final stage of lysozyme action at pH 5 no cell debris but stabilized protoplasts were to be seen without detectable alterations of the primary shape of the cells. At the same time long extended ribbon-like structures appeared outside the bacteria. The origin as well as the chemical nature of this material is discussed. Furthermore, immunological implications are considered.     

An oat coleoptile wall protein that induces wall extension in vitro and that is antigenically related to a similar protein from cucumber hypocotyls

Plant cell walls expand considerably during cell enlargement, but the biochemical reactions leading to wall expansion are unknown. McQueen-Mason et al. (1992, Plant Cell 4, 1425) recently identified two proteins from cucumber (Cucumis sativus L.) that induced extension in walls isolated from dicotyledons, but were relatively ineffective on grass coleoptile walls. Here we report the identification and partial characterization of an oat (Avena sativa L.) coleoptile wall protein with similar properties. The oat protein has an apparent molecular mass of 29 kDa as revealed by sodium dodecyl sulfate-polyacrylamide gel eletrophoresis. Activity was optimal between pH 4.5 and 5.0, which makes it a suitable candidate for acid growth responses of plant cell walls. The oat protein induced extension in walls from oat coleoptiles, cucumber hypocotyls and pea (Pisum sativum L.) epicotyls and was specifically recognized by an antibody raised against the 29-kDa wall-extension-inducing protein from cucumber hypocotyls. Contrary to the situation in cucumber walls, the acid-extension response in heat-inactivated oat walls was only partially restored by oat or cucumber wall-extension proteins. Our results show that an antigenically conserved protein in the walls of cucumber and oat seedlings is able to mediate a form of acid-induced wall extension. This implies that dicotyledons and grasses share a common biochemical mechanism for at least part of acid-induced wall extensions, despite the significant differences in wall composition between these two classes of plants.Abbreviations ConA concanavalin A - CM carboxymethyl - DEAE diethylaminoethyl - DTT dithiothreitol - Ex29 29-kDa expansin     

Cell Expansion and Wall pH in the Fern Regnellidium diphyllum, A Plant Lacking Acidinduced Growth

Petioles of the semi-aquatic fern Regnellidium diphyllum donot show acid growth but low wall pH is a necessary conditionfor maximum rates of IAA-induced cell expansion. Measurementsof wall pH by two indirect methods indicate an unusually lowvalue, in the range pH 4 to 5. This is one to two pH units belowthat estimated for petioles of the semi-aquatic dicotyledonNymphoides peltata, a species in which IAA aand ethylene causegrowth responses very similar to those in Regnellidium but whereacid growth occurs. Having shown previously that fusicoccinenhances proton secretion in both Regnellidium and Nymphoides,we now show that although it causes a reduction in the estimatedapoplast pH to below 4·0 in Regnellidium, cell expansionis not promoted. The FC-induced reduction in pH in Nymphoidesis less and occurs more slowly, but growth is promoted significantly;when IAA and fusicoccin are present together, growth promotionis approximately additive for Nymphoides A model is proposed for Regnellidium in which equilibrium wallpH is maintained at a low value that is optimal for acid growth,the availability of acid-labile sites in the wall being thechief limitation to cell extension. We suggest that this controlmechanism may be widespread for organs without a cuticle, includingroots and the gametophytes of lower plants growing in acidicconditions. Key words: Acid growth, wall pH, fusicoccin, Regnellidium diphyllum, Nymphoides peltata     

Effects of organic pH buffers on a cell growth and an antibody production of human-human hybridoma HB4C5 cells in a serum-free culture

Human-human hybridoma cells secreting a human monoclonal antibody were cultured in a serum-free medium containing various organic pH buffers in order to clarify their effects on cell growth and antibody production. Organic pH buffers having either one sulfonic acid and several acyclic amine moieties, or several cyclic amine moieties containing two amino nitrogen did not inhibit cell growth; while other organic buffers sulfonic acid moiety plus several cyclic amine moieties containing one amino nitrogen slightly decreased cell growth, but enhanced antibody production. Using Fujita's organic conceptual diagram, a relationship between the organicity and inorganicity of a pH buffer to cell growth and antibody production was found. pH buffers with large inorganicity and small organicity values were favorable for cell growth, and buffers with small inorganicity and large organicity values were preferred to enhance antibody production. Although the pH buffering range affects cell growth, its effect on antibody production is not clear. In conclusion, 2-morpholinoethanesulfonic acid (MES), 3-morpholino-propanesulfonic acid (MOPS) and 1, 2-N, N-bis[N, N-di(2-sulfonoethyl)piperazinyl]ethane (Bis-PIPES) are shown to be the most optimal of the buffers tested, because they enhanced antibody production without decreasing the cell growth among the pH buffers tested here.     

Does indoleacetic acid promote growth via cell wall acidification?

Growth of Triticum aestivum L. cv. Cappelle Desprez coleoptiles is promoted by 5.7×10^–5 M indole acetic acid (IAA) as effectively in pH 3.4 buffer as in water, but IAA is not effective in the presence of buffer at pH 3.0 or 3.2 A combination of 5.7×10^–5 M IAA and pH 3.4 buffer promotes growth to a greater extent than pH 3.2 buffer alone, which is optimal for acid-induced growth. IAA employed at 10^–7 M is still effective at promoting growth in the presence of pH 3.4 buffer, moreover, IAA at 10^–7 M interacts synergistically with the acidic buffer to promote growth. It is concluded that IAA and acid promote growth via separate mechanisms, and that IAA does not promote cell wall loosening by rendering the cell wall more acid.Abbreviation IAA Indoleacetic acid     

Invertase activity associated with the walls of Solanum tuberosum tubers

Three fractions with invertase activity (beta-D-fructofuranoside fructohydrolase, EC 3.2.1.26) were isolated from mature Solanum tuberosum tubers: acid soluble invertase, invertase I and invertase II. The first two invertases were purified until electrophoretic homogeneity. They are made by two subunits with an apparent M(r) value of 35,000 and their optimal pH is 4.5. Invertase I was eluted from cell walls with ionic strength while invertase II remained tightly bound to cell walls after this treatment. This invertase was solubilized by enzymatic cell wall degradation (solubilized invertase II). Their K(m)s are 28, 20, 133 and 128 mM for acid soluble invertase, invertase I, invertase II and solubilized invertase II, respectively. Glucose is a non-competitive inhibitor of invertase activities and fructose produces a two site competitive inhibition with interaction between the sites. Bovine serum albumin produces activation of the acid soluble invertase and invertase I while a similar inhibition by lectins and endogenous proteinaceous inhibitor from mature S. tuberosum tubers was found. Invertase II (tightly bound to the cell walls) shows a different inhibition pattern. The test for reassociation of the acid soluble invertase or invertase I on cell wall, free of invertase activity, caused the reappearance of all invertase forms with their respective solubilization characteristics and molecular and kinetic properties. The invertase elution pattern, the recovery of cell wall firmly bound invertase and the coincidence in the immunological recognition, suggest that all three invertases may be originated from the same enzyme. The difference in some properties of invertase II and solubilized invertase II from the other two enzymes would be a consequence of the enzyme microenvironment in the cell wall or the result of its wall binding.     

The Existence of Expansin and Its Properties in the Hypocotyls of Soybean Seedlings

Expansins, a newly discovered class of cell wall proteins, were the only proteins that, to date, have been shown to have the ability to restore the "acid growth" response of the heat-inactivated cell wall in an in vitro assay. In order to characterize these proteins, an automatic extensometer had been previously constructed by modification of an equal-arm mechanical balance with a linear variable differential transformer (LVDT) and with some easily available laboratory equipment. The objective of this study was to confirm and complement the work on expansin in cucumber ( Cucumis sativus L. ) seedlings carried out in the expansin-discoverers' laboratory and in addition, to further examination of the extensometer built in the authors' laboratory. It was reported that, firstly, expansin activity was maximal in cell wall from the growing region of soybean (Glycine max L. ) hypocotyls but was negligible or lacking in that from mature, basal regions and cotyledons. Corre- spondingly, walls from the growing tissue had a strong susceptibility to the action of expansin, whereas the nongrowing tissues became insensitive to the expansin action. It was concluded that the growth of soybean hypocotyl was associated with an increase in both expansin activity and wall susceptibility to the expansin action. Secondly, the heat-inactivated wall extension could be induced by cross reconstitution with crude expansin extract between soybean and cucumber species. Thirdly, once the heat-inactivated wall has been pretreated with the exogenous expansin, the reconstituted wall required no further expansin for extension indicating that exogenous expansin could specifically bind to cell wall and be enough to repeatedly exert its action without releasing from the cell wall into the external solution, i.e., a single expansin molecule could gradually break a series of load-bearing bonds one by one while moving along the cell wall, and thereby permitting the wall to extend. Fourthly, reconstitution of the wall extension activity was evidently dependent on the expansin concentration and the pH of the bathing solution, which was consistent with the catalytic characteristics of classical enzymes. Finally, endogenous and reconstituted wall extension could be significantly induced in 50 mmoL/L sodium acetate at pH 4.5 and completely inhibited in 50 mmol/L Hepes at pH 6.8, especially these phenomena could continuously be caused by switching incubation buffer from one to the other alternately, suggesting that change in pH of bathing solution could only affect the conformation of expansin (thus leading to denaturation or renaturation of it) but not the affinity of it for cell wall. In summary, these observations lend further support to the fact that expansin could mediate the acid-induced extension of the isolated wall, probably through a biochemical or enzymatic process exerting directly to the cell wall. This protein may play an essential role in the control of plant cell growth in vivo.     

Measuring Plant Cell Wall Extension (Creep) Induced by Acidic pH and by Alpha-Expansin

Growing plant cell walls characteristically exhibit a property known as ''acid growth'', by which we mean they are more extensible at low pH (< 5) ¹. The plant hormone auxin rapidly stimulates cell elongation in young stems and similar tissues at least in part by an acid-growth mechanism ^{2, 3}. Auxin activates a H⁺ pump in the plasma membrane, causing acidification of the cell wall solution. Wall acidification activates expansins, which are endogenous cell wall-loosening proteins ⁴, causing the cell wall to yield to the wall tensions created by cell turgor pressure. As a result, the cell begins to enlarge rapidly. This ''acid growth'' phenomenon is readily measured in isolated (nonliving) cell wall specimens. The ability of cell walls to undergo acid-induced extension is not simply the result of the structural arrangement of the cell wall polysaccharides (e.g. pectins), but depends on the activity of expansins ⁵. Expansins do not have any known enzymatic activity and the only way to assay for expansin activity is to measure their induction of cell wall extension. This video report details the sources and preparation techniques for obtaining suitable wall materials for expansin assays and goes on to show acid-induced extension and expansin-induced extension of wall samples prepared from growing cucumber hypocotyls.To obtain suitable cell wall samples, cucumber seedlings are grown in the dark, the hypocotyls are cut and frozen at -80 °C. Frozen hypocotyls are abraded, flattened, and then clamped at constant tension in a special cuvette for extensometer measurements. To measure acid-induced extension, the walls are initially buffered at neutral pH, resulting in low activity of expansins that are components of the native cell walls. Upon buffer exchange to acidic pH, expansins are activated and the cell walls extend rapidly. We also demonstrate expansin activity in a reconstitution assay. For this part, we use a brief heat treatment to denature the native expansins in the cell wall samples. These inactivated cell walls do not extend even in acidic buffer, but addition of expansins to the cell walls rapidly restores their ability to extend.Open in a separate windowClick here to view.^{(58M, flv)}     

Acid-induced wall loosening is confined to the accelerating region of the root growing zone

The aims of this study were to quantify developmental differences in acid growth along the root axis and to determine whether these differences were due to alterations in cell turgor or cell wall properties. The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m^-3 citrate-phosphate buffer or unbuffered solutions. Whole root elongation rate rapidly increased and measurement of the local growth profile indicated that this increase in growth occurred in young cells in the accelerating zone (apical 0-4 mm) while more proximal growing cells were unaffected. Unbuffered solutions of identical pH produced qualitatively similar results. Single cell turgor pressures were unchanged between pH treatments both longitudinally and radially in the root tip. This suggests that the rapid acid-induced changes in growth rate were due to an increase in cell wall loosening. Single cell osmotic pressure and water potential were not significantly different between pH treatments. Acid pH caused net solute import at the root tip to increase 3- to 4-fold, which, coupled with the maintenance of turgor and osmotic pressure, indicated that solute import was not limiting expansion. Thus, acidic solutions cause an increase in growth in accelerating but not decelerating regions. It has been shown for the first time that acid growth in intact, growing roots is not due to differences in turgor, assigning these changes to cell wall properties. Possible cell wall biochemical alterations are discussed.     

Analysis of Cell Wall Constituents of Biocide-Resistant Isolates from Dental-Unit Water Line Biofilms

In past years, the significance of microbial resistance to biocides has increased. Twenty biocide-resistant bacterial strains were isolated from dental-unit water line biofilm. All strains resisted high biocide concentrations (up to 100 mug ml(-)1): sodium dodecyl sulphate, hydrogen peroxide, sodium hypochlorite, phenol, Tween 20, ethylenediaminetetraacetic acid, chlorohexidine gluconate, and povidine iodine. Among bacteria, biocide sensitivity is based on permeability of biocides through the cell wall. Gram-positive bacteria are more permeable and susceptible to biocides, whereas Gram-negative bacteria have a more complex cell wall and are the least sensitive bacteria. The present study was designed to study the effect of biocides on the cell wall of biocide-resistant bacteria. Peptidoglycan (PG), diaminopimelic acid (DAP), and teichoic acid contents of the cell wall were determined in L-broth and L-broth supplemented with biocides at different temperatures (37 degrees C and 45 degrees C) and pH levels (7 and 9). In general and Gram staining-specific comparison, a significant increase (p < 0.05) in the DAP content of biocide-resistant bacteria was observed at pH 7 and at both temperatures. In tubing-specific comparison, a significant increase in the amount of teichoic acid in air water tubing (37 degrees C at pH 9) and DAP in patient tubing (pH 7 at both temperatures) was observed. In main water pipe, a significant decrease (p > 0.05) in PG content was noticed at 45 degrees C and pH 9. Overall, a significant increase in DAP content may be an important constituent in the manifestation of isolate resistance against various biocides.     

The Acid Growth Theory of auxin-induced cell elongation is alive and well

Plant cells elongate irreversibly only when load-bearing bonds in the walls are cleaved. Auxin causes the elongation of stem and coleoptile cells by promoting wall loosening via cleavage of these bonds. This process may be coupled with the intercalation of new cell wall polymers. Because the primary site of auxin action appears to be the plasma membrane or some intracellular site, and wall loosening is extracellular, there must be communication between the protoplast and the wall. Some "wall-loosening factor" must be exported from auxin-impacted cells, which sets into motion the wall loosening events. About 20 years ago, it was suggested that the wall-loosening factor is hydrogen ions. This idea and subsequent supporting data gave rise to the Acid Growth Theory, which states that when exposed to auxin, susceptible cells excrete protons into the wall (apoplast) at an enhanced rate, resulting in a decrease in apoplastic pH. The lowered wall pH then activates wall-loosening processes, the precise nature of which is unknown. Because exogenous acid causes a transient (1-4 h) increase in growth rate, auxin must also mediate events in addition to wall acidification for growth to continue for an extended period of time. These events may include osmoregulation, cell wall synthesis, and maintenance of the capacity of walls to undergo acid-induced wall loosening. At present, we do not know if these phenomena are tightly coupled to wall acidification or if they are the products of multiple independent signal transduction pathways.     

Some Properties of the Autolytic N-Acetylmuramidase of Lactobacillus acidophilus

The autolytic N-acetylmuramidase present in Lactobacillus acidophilus strain 63 AM Gasser has an optimal pH between 5 and 6 when lysing intact cells or isolated cell walls. Cellular lysis at pH 5 is two to four times more rapid in citrate buffer of 0.01 M and 0.5 M or higher than in 0.1 M acetate buffer. It seems that sulfhydryl groups are required for both cell and wall autolysis. Heavy metal ions and p-chloro-mercuribenzoate, at low concentrations, are powerful inhibitors. Ethylenediaminetetraacetic acid stimulates cellular but not wall autolysis in acetate buffer to the level obtained in citrate buffer. The possible involvement of sulfhydryl groups in a mechanism of control of cellular autolytic activity is discussed. The autolytic enzyme, although unstable in solution at 37 C, can be extracted from walls by the use of solutions of bovine serum albumin (100 mug/ml) in 0.01 N NaOH. Soluble enzyme extracted from walls rebinds on to sodium decylsulfate-treated walls, but three times as much of the wall material is required to completely re-adsorb the activity.     

Structural changes during lysis of a psychorophilic marine bacterium

The marine psychrophile, a red, gram-negative motile rod with a single polar flagellum, is stable when suspended in 0.1 m Mg(2+) plus 0.5 m NaCl at 0 C and neutral pH but lyses if the salt composition of the medium is changed, the temperature raised above 20 C, or the pH lowered. Lysis is accompanied by a fall in turbidity, a release of ultraviolet-absorbing substances, and a loss of deoxyribonucleic acid and ribonucleic acid. Ultrastructural changes accompanying lysis were studied. Thin sections of cells fixed while intact showed a triple-layered cell wall and cytoplasmic membrane, each 6.0 to 7.5 nm thick. Mesosomes were also observed. Either Na(+) or Mg(2+) could maintain wall integrity, whereas Mg(2+) was needed for membrane integrity. In distilled water, lysis was very extensive, and much material was released as wall fragments and as vesicles which probably came from the wall and cytoplasmic membrane. Lysis at 37 C resulted in degradation of the wall and liberation of wall fragments. The cell membrane was rarely observed as a triple-layered structure in such temperature-lysed cells. After lysis at pH 5.0, the cell wall was distorted, and only a suggestion of the cell membrane remained. Replicas showed that this organism had a matted surface which was distorted under different conditions of lysis.     

Fervidobacterium nodosum gen. nov. and spec. nov., a new chemoorganotrophic,caldoactive, anaerobic bacterium

A new species of extremely thermophilic, glycolytic anaerobic bacterium, Fervidobacterium nodosum isolated from a New Zealand hot spring, is described. Fervidobacterium nodosum strains were Gram-negative, motile, non-sporulating obligately anaerobic rods that existed singly, in pairs or in chains. Electron micrographs of thin sections revealed a two-layered cell wall structure. The outer layer of the cell wall produced spheroids, which was a typical feature of this organism. The optimum temperature for growth was 65 to 70° C, the maximum 80° C and the minimum greater than 40° C. Growth occurred between a pH of 6.0 and 8.0 with the optimum being 7.0 to 7.5. The doubling time of Fervidobacterium nodosum at optimal temperature and pH was 105 minutes. The DNA base composition was 33.7% guanine plus cytosine as determined by thermal denaturation. A wide range of carbohydrates including glucose, sucrose, starch and lactose could be utilized by the organism. Lactate, acetate, hydrogen, and carbon dioxide were the major end products of glucose fermentation with lesser amounts of ethanol being formed. Growth was inhibited by tetracycline, penicillin and chloramphenicol indicating that the organism was a eubacterium.     

Promotion of Xyloglucan Metabolism by Acid pH

Like indoleacetic acid, buffers of acidic pH, which stimulate elongation of pea (Pisum sativum var. Alaska) stem tissue, induce the appearance within the tissue of a watersoluble xyloglucan polymer that probably arises from previously deposited wall material. Neutral pH buffers, which inhibit the elongation response to indoleacetic acid in this tissue, inhibit indoleacetic acid-induced increase in soluble xyloglucan. The findings provide further evidence that release of soluble xyloglucan from the cell walls of pea results from the biochemical action on the cell wall that is responsible for wall extension. The data also indicate that treatment of tissue with either auxin or acidic pH has a similar biochemical effect on the cell wall. This is consistent with the H⁺ secretion theory of auxin action.