Physicochemical and in situ observations on the adhesion of gliding bacteria to surfaces

The ability of Flexibacter BH3 to adhere to solid surfaces and to overcome the horizontal drag involved in gliding across the surfaces was considered in terms of the Stefan adhesion principle. The extracellular slime produced by Flexibacter BH3 was suitable as a Stefan adhesive because it exhibited viscous properties characteristic of a linear colloid, increasing the adhesiveness of the bacterium but allowing translational motion across the surface. The water-soluble slime was a glycoprotein, containing glucose, fucose, galactose and some uronic acid. Vesicles and tubules on the outer surface of Flexibacter BH3 possessed trilaminar membranes, contained 2-keto-3-deoxyoctonate (KDO), and showed identity with phenol-extracted lipopolysaccharide (LPS) in gel-diffusion tests.Sections of Flexibacter BH3 gliding on a gold film overlaying an agar medium reveraled a highly convuluted cell envelope outer membrane, portions of which closely conformed to the microcontours of the gold surface. Possible mechanisms of gliding are discussed in relation to this close association with solid surface features, to the finding that flexibility and spiral motion are not essential for gliding, and to evidence revealing the extrusion of slime in advance of pathfinder bacteria.Abbreviations used KDO 2-keto-3-deoxyoctonate - LPS lipopolysaccharide     

Distribution of iron in Lake Banyoles in relation to the ecology of purple and green sulfur bacteria

The distribution of iron both in suspended sediment and in the water column has been studied during summer stratification in Lake Banyoles. In this lake, near bottom springs, a very fine material suspended sediment remains in suspension. Dissolved Fe²⁺ in interstitial water of this suspended sediment, is related to redox potential and to the bottom water inflow. In the water column, soluble iron is present in the hypolimnion of the six different basins forming Lake Banyoles. Under those conditions Fe²⁺ is partially removed by sulfide produced in the anoxic sediment. In addition, a peak of Fe²⁺ found at the density gradient level in basins C-III, C-IV and C-VI. A three compartment model on the dynamics of the processes involving iron in Lake Banyoles is proposed. The bottom springs supply oxygen to the anoxic hypolimnion affecting chemical processes of the iron cycle. The presence of phototrophic sulfur bacteria in the anoxic monimolimnion of basins C-III and C-IV can be related to the kinetics of Fe²⁺ and sulfide. In C-III sulfide concentration exceeds Fe²⁺ concentration whereas in C-IV sulfide is not detectable and iron reached values up to 60 mM. The presence of phototrophic sulfur bacteria in iron-containing environments with no detectable sulfide is explained by the ability of such microorganisms to use FeS as electron donor instead of H₂S.     

Infection characteristics of a trematode in an estuarine isopod: influence of substratum

The estuarine isopod Cyathura carinata is a second intermediate host to microphallid trematodes, which use mud snails Hydrobia spp. and shorebirds as respectively first intermediate and final hosts. To identify processes responsible for infection patterns observed in C. carinata, a short-term microcosm experiment was conducted with both macroinvertebrates and one of their common parasites – Maritrema subdolum. Fine sand collected from two different shallow water sites was used to test if sediment type could affect infection rates. After 7 days at 25 °C, C. carinata from the substratum with the highest proportion of particles <125 m were more surface active and obtained significantly more M. subdolum individuals than isopods from the other sediment type. No parasite-induced effects on the hosts were found during this short-term experiment. The distribution pattern of microphallid cysts and mesocercariae inside the isopods revealed that M. subdolum cercariae primarily penetrated through the pleopods and afterwards located themselves in the middle-posterior region of the hosts body. Even if it was not possible to identify the factor responsible for the observed infection patterns (cercariae production and/or host behaviour), the results of this experiment indicate that small-scale factors, such as differences in substratum and associated features, may have considerable impact on infections of host populations.     

Growth of Daphnia longispina L. in a polyhumic lake under various availabilities of algal,bacterial and detrital food

The availability and importance of food sources for growth of Daphnia longispina L. from a highly coloured fishless lake with anoxic hypolimnion were assessed by combining in situ and laboratory experiments. In in situ experiments populations were enclosed in tubes with natural temperature stratification and with or without anoxic hypolimnion. In the laboratory experiments the importance of food source (littoral zone vs pelagic epilimnion) was assessed by enclosing moss thalli and a natural zooplankton population in a large-scale flow-through system supplying food for experimental Daphnia. Growth of juveniles of Daphnia in epilimnetic water was determined in batch culture experiments and the importance of increasing concentrations of bacteria and algae for their growth and development was investigated with a small-scale flow-through system. Access to the anoxic hypolimnion enhanced the growth of Daphnia by 23–24%. Growth rates in the tubes with anoxic hypolimnion were 0.36 and 0.16 d^–1 in July and August respectively. In tubes without anoxia the corresponding values were 0.29 and 0.13. In batch-cultures the highest growth rate determined was 0.16 and the overall rates were lower than in in situ experiments. In batch culture Daphnia was able to grow in darkness for 10 days with a rate of 0.16. In the large-scale flow-through system Daphnia population fed with littoral water reproduced well despite the low concentration of algae and increased its number by a factor of c. 32 in 10 days. However, the animals were small and net production of Daphnia population thus lower under the littoral influence than in the control treatment. Population could survive and grew slowly on pelagial water processed by a natural zooplankton community and with very little algae left. It is thus possible that bacteria serve as a life-support system enabling the population survival over periods of algal shortage. Small-scale flow-through experiments revealed that Daphnia longispina is able to mature and reproduce on a bacterial diet if the food concentration is high enough and Daphnia on bacterial food could achieve growth rates similar to those on an algal diet. The threshold food level for Daphnia longispina was estimated to be c. 18.5 g C 1^–1. Detrital material is of limited value in nutrition of Daphnia even in a lake where more than 75% of carbon is bound in particulate detritus.     

Flagella-dependent gliding motility inChlamydomonas

Summary Flagella are generally recognized as organelles of motility responsible for the ability ofChlamydomonas to swim through its environment. However, the same flagella are also responsible for an alternative form of whole cell locomotion, termed gliding. Use of paralyzed flagella mutants demonstrates that gliding is independent of axonemal bend propagation. Gliding motility results from an interaction of the flagellar surface with a solid substrate. Gliding is characterized by bidirectional movements at 1.6±0.3 m/second and occurs when the cell is in a characteristic gliding configuration, where the two flagella are oriented at 180° to one another. A variety of observations suggest that the leading flagellum is responsible for the force transduction resulting in cell locomotion, although both flagella have the capacity to function as the active flagellum. The characteristics of gliding motility have been compared with theChlamydomonas flagellar surface motility phenomenon defined as surface translocation of polystyrene microspheres.     

The physical, chemical and biological characteristics of the holomictic sulphated Lake Arcas-2 (Cuenca, Spain)

The main limnological features of Lake Arcas-2 were followed through two consecutive stratification periods. Its morphometrical characteristics, such as the high relative depth (31%) and steep basin walls, enhance the sharp water stratification with the formation of an oxic-anoxic boundary at 8.8–9 m and a sulphide-rich hypolimnion during the thermal stagnation. The ionic sequence was SO ₄ ^2- >Alkal.>Cl^- and Ca²⁺>Mg²⁺>Na⁺>K⁺ and the mineralization was high, with water conductivity higher than 2500 S cm^-1. It is mesotrophic with epilimnetic chlorophyll a concentrations of 2–5 g l^-1 and metalimnetic of 8 g l^-1. The depth of the euphotic zone was established at around 8 m. Phosphorus concentration in the oxic waters was low but largely accumulated in the anoxic hypolimnion, together with other compounds such as ammonium, silicate, sulphide, etc. Nitrate was abundant in the oxic waters and is related to the use of fertilizers in the surrounding fields. A fine-layer sampler was used to study the oxic–anoxic interface where a dense plate of Chromatiaceae developed. The dominant species, Chromatium weissei, reached a maximum integrated biomass of 121 gWW m^-2 during August. Thiocapsa sp., representing less than 1% of total purple bacteria, had an integrated biomass of 0.8 gWW m^-2 and Amoebobacter sp. (1%) had 1 gWW m^-2. Other populations were sharply stratified i.e. Oscillatoria cf. ornata and Cryptomonas erosa. Those organisms, and mainly the cyanobacterium, accounted for the high chlorophyll a concentrations (>100 g l^-1) recorded in the anoxic waters of the hypolimnion. Green bacteria were scarcely developed due to the shadowing effect caused mainly by the purple bacterial bloom.     

Structure of root nodules formed by Rhizobium on the non-legume Trema cannabina var. scabra

The structure of the nodules formed by Rhizobium on the non-legume Trema cannabina var. scabra was studied using the light microscope. The overall features of the nodules showed greater resemblance to the non-legume rather than the legume nodule. Nodule squashes yielded bundles of infection threads and bacteroids with morphological differences from rhizobial cells grown on yeast-mannitol-glucose agar. Two types of cell infection occurred within the bacterial zone; plant cells were either, like legumes, filled with rhizobia released from the infection threads (less than one third of infected cells) or were filled with the extensive growth and development of the infection thread. The rate of nitrogen fixation in the Trema nodule was high. It seemed that host cells filled with threads were active in N fixation.     

Chitosome-like vesicles from gamma particles of Blastocladiella emersonii synthesize chitin

When gamma particles isolated from the aquatic fungus, Blastocladiella emersonii, were incubated in a supernatant derived from a homogenate of zoospores previously triggered to encyst with 50 mM KCl, they exhibited a three-fold increase in chitin synthetase activity and produced chitosome-like vesicles. Passage of such vesicles through a linear sucrose gradient resulted in a symmetrical distribution of chitin synthetase activity over a broad portion of the gradient, and the specific activity of the peak fraction was seven times greater than that of the gamma particles. After isopycnic sucrose gradient centrifugation, chitin synthetase activity occurred in a band of particles with a peak buoyant density of 1.18 g/cm³. Ultrastructural examination of negatively stained samples from the peak fraction revealed spheroidal, chitosome-like particles 70–120 nm in diameter. Suspension of these particles produced chitin microfibrils when incubated with uridine diphosphate N-acetylglucosamine, the substrate for chitin synthetase.Non Standard Abbreviations Used GlcNAc N-acetylglucosamine - UDP-GlcNAc uridine diphosphate N-acetylglucosamine - PYG agar 1.25 g of peptone, 1.25 g of yeast extract, 3 g of glucose, and 20 of agar per 1000 ml of water, the pH being adjusted to 6.8 with KOH after autoclaving - EGTA ethyleneglycol-bis (-aminoethylether)-N,N-tetraacetic acid     

Impact of winter reed harvesting and burning on the nutrient economy of reed beds

The fringing reeds (Phragmites australis (Cav.) Trin. ex Steud., Poaceae) at Lake Constance-Untersee were mown or burnt in winter thereby drastically reducing the addition of decomposable organic matter to the sediment. The purpose of this study was to test whether or not this management significantly decreased the contents of organic matter and nutrients in the surface sediment layer and if the oxygen conditions in the withinreed water body improved. Hypotheses were tested by monitoring 6 treated reed beds and 3 reference fields over a period of up to 4 years. The sediment/water system of reed beds was found to be well buffered against the removal of the current year's crop of dead Phragmites straw, because only slight, and mostly insignificant, differences between treated and untreated reeds were detected. Hence, the benefit of winter reed harvesting to reduce nutrient overloading of the reed-belts and the die-back of reeds remains dubious.     

Endophytic fungi from Musa acuminata leaves and roots in South China

One hundred and sixty-three endophytic fungal cultures were isolated from 200 leaf samples of Musa acuminata trees, which were soaked in 36% formaldehyde solution for surface sterilization. They belonged to the genera of Gloeosporium musae (45%), Myxosporium spp. (11%), Deightoniella torulosa (8.5%), Alternaria tenuis (7.9%), Sphaceloma spp. (7.4%), Aureobasidium spp. (4.3%), Melida spp. (1.8%), Uncinula spp. (1.8%), Penicillium spp. (1.8%), Aspergillus spp. (1.2%), Sarcinella spp. (1.2%), Cladosporium sp. (0.6%), Cephalosporium sp. (0.6%) and sterile mycelium (6.7%). Sixty-eight endophytic fungal cultures were isolated from 100 root samples. They respectively belonged to the genera of Aspergillus spp. (31%), Paecilomyces spp. (16%), Penicillium spp. (15%), Fusarium spp. (10%), Gloeosporium musae (6%), yeast (3%), Deightoniella torulosa (3%), Spicaria sp. (1.4%), Cephalosporrium sp. (1.4%), Meliola sp. (1.4%) and sterile mycelium (10%). Water agar (containing 50 g chloramphenicol ml^–1 and 50 g streptomycin ml^–1) seemed to be a better medium for isolation of endophytic fungi than potato-dextrose agar (PDA, containing 50 g chloramphenicol ml^–1 and 50 g streptomycin ml^–1).     

Lipids of the marine bacterium Flexibacter polymorphus

This paper reports on the total fatty acid composition of a marine bacterium representative of the genus Flexibacter. Flexibacter polymorphus is unusual in containing a high proportion of the polunsaturated acid C20:53 whilst the level of branched fatty acids is low. These facts suggest that the membrane flexibility necessary for its gliding motility is a function of the polyunsaturated fatty acid composition. Biosynthetic precursors to the C20:5 acid are present which are characteristic of an oxygen-dependent pathway. The fatty acid composition of the structural lipids is influenced by changes in the culture medium. Na₂S inhibits production of the C20:5 acid at levels much lower than that at which it is known to inhibit growth. The intracellular granules observable in F. polymorphus do not contain elemental sulphur, in contrast to Beggiatoa sps., but instead probably contain lipids.     

Structural specificity of sugars that inhibit gliding motility of Cytophaga johnsonae

It is a common observation that gliding bacteria form raised, smooth-edged colonies on nutrient-rich media, and typical thin, spreading, uneven-edged colonies on nutrient-poor media. An earlier study of the effect of different sugars on colony spreading by Cytophaga johnsonae was expanded to include the effects of several sugars and other organic compounds on the motility of groups of cells (rafts), and latex bead movement on cells' surfaces. When the structures of those sugars that did, or did not, affect raft formation and colony spreading were compared, it was noted that those sugars that inhibited these two manifestations of gliding motility all possessed a common sub-structure, that found in the portion of glucopyranose comprising carbons 3, 4, 5, and 6. If these structural features were altered chemically or stereochemically, the resulting molecule had little to no effect on motility. The differential effects of some compounds on raft formation, colony spreading, and bead movement are noted. A regulatory mechanism that would turn off motility in the presence of an inhibitory sugar is implicated, and the relevance of such a system to the life of the organism is discussed. We report, as well, additional compounds that will serve as carbon and energy sources for C. johnsonae.     

Sedimentary photosynthetic pigments of algae and phototrophic bacteria in Lake Hamana,Japan: temporal changes of anoxia in its five basins

We analyzed photosynthetic pigments of algae and bacteria (phototrophic sulfur bacteria: Chromatium and brown Chlorobium) in sediment cores and water samples obtained from five basins of Lake Hamana, a brackish, eutrophic, holomictic lake in Japan, and discussed our findings in relation to the distribution of the phototrophs. The four outer basins are connected to the central basin by narrow inlets. The prevalence of anoxia in Lake Hamana was demonstrated by the widespread presence of bacterial pigments in each core. The construction of training walls in 1954–1956 to direct tidal currents into the lake via Imagire-guchi Channel, the sole inlet for seawater, increased the lake water circulation, suppressed the development of anoxia, and caused Chromatium to disappear. Strong correlations (r ² 0.7) between total algal carotenoid (TAC) and total bacterial carotenoid (TBC) contents in each core were found in four basins. We ascribe this to the induction of anoxia by water stratification and algal proliferation, which precede the growth of phototrophic sulfur bacteria in the deeper layers of the water column. The slopes of the TBC–TAC correlations in the sediment cores, indicating the extent and stability of anoxia at each site, differed among basins (0.23–0.67) and were inversely related to the exchange rate of water by seawater intrusion in each basin.     

Colonisation par les micro-organismes,evolution chimique des feuilles de différentes espèces d'arbres (peuplier,aulne, myrique) dans des eaux oligotrophes du Bouclier canadien et incidence sur leur utilisation par les macro-invertébrés

Myrica gale, Alnus rugosa and Populus tremuloides leaves were incubated in situ in the oligotrophic acid waters of the Canadian Shield (James Bay, Quebec) in order to follow microorganic decomposition, respiration and chemical transformations.Respiratory activities in decomposing speckled alder and trembling aspen leaves were more important than that in sweet gale. In spite of low nutrient concentrations in the water, nitrogen concentration increased in the three species while phosphorus levels increased only in the speckled alder during decomposition.

     

Current state of seaweed resources in Spain

Commercial seaweeds in Spain are harvested on the north and northwest coasts. They are mainly agarophytes and carrageenophytes (Gelidium spp. and some Irish moss-like species, respectively), although some Phaeophyceae species (Fucus spp. and Laminaria spp.) are also exploited for alginates. No industrial seaweed cultivation is carried out in Spain at present. Spain's total commercial seaweed harvest can be estimated at 6,528 ± 2,076 t dry wt year^–1. Gelidium spp. are by far the most harvested, attaining 5,135 ± 1,761 t dry wt y^–1. To date, Spain's commercial seaweed harvest is low compared with that of other countries, but data on field standing crops and productivities of commercial taxa suggest that harvesting could be increased greatly.     

Gliding motility of Babesia bovis merozoites visualized by time-lapse video microscopy

Background

Babesia bovis is an apicomplexan intraerythrocytic protozoan parasite that induces babesiosis in cattle after transmission by ticks. During specific stages of the apicomplexan parasite lifecycle, such as the sporozoites of Plasmodium falciparum and tachyzoites of Toxoplasma gondii, host cells are targeted for invasion using a unique, active process termed “gliding motility”. However, it is not thoroughly understood how the merozoites of B. bovis target and invade host red blood cells (RBCs), and gliding motility has so far not been observed in the parasite.

Methodology/Principal Findings

Gliding motility of B. bovis merozoites was revealed by time-lapse video microscopy. The recorded images revealed that the process included egress of the merozoites from the infected RBC, gliding motility, and subsequent invasion into new RBCs. The gliding motility of B. bovis merozoites was similar to the helical gliding of Toxoplasma tachyzoites. The trails left by the merozoites were detected by indirect immunofluorescence assay using antiserum against B. bovis merozoite surface antigen 1. Inhibition of gliding motility by actin filament polymerization or depolymerization indicated that the gliding motility was driven by actomyosin dependent process. In addition, we revealed the timing of breakdown of the parasitophorous vacuole. Time-lapse image analysis of membrane-stained bovine RBCs showed formation and breakdown of the parasitophorous vacuole within ten minutes of invasion.

Conclusions/Significance

This is the first report of the gliding motility of B. bovis. Since merozoites of Plasmodium parasites do not glide on a substrate, the gliding motility of B. bovis merozoites is a notable finding.     

Neutral gravitaxis of gliding Loxodes exposed to normal and raised gravity

Summary In the statocystoid-bearing, flat ciliate Loxodes, the peculiar steady locomotion on submersed substrates (called gliding) was investigated between 1 g and 5.4 g under controlled environmental conditions in a centrifuge microscope. Videorecordings of the movements of large cell populations were processed with an automated analysis procedure. At 1 g, possible sedimentation was fully compensated, and vertical shifts of the population were neutralized because upward and downward orientations of the cells occurred at equal proportions (neutral gravitaxis). With rising gravity the resultant velocity of upward-gliding cells remained unchanged, whereas the velocity of downward-gliding cells increased continuously. Long-term exposure to hypergravity did not generate detectable signs of adaptation. The bipolar orientation of Loxodes persisted even under fivefold normal gravity, but the axis of orientation rotated from the gravity axis in the counterclockwise direction. The data suggest that both gravikinesis and graviorientation of gliding Loxodes are instrumental in perfect neutralization of sedimentation at terrestrial conditions.     

Oxygen consumption and ammonia accumulation in the hypolimnion of Walker Lake, Nevada

Walker Lake (area = 140 km², Z _mean = 19.3 m) is a large, terminal lake in western Nevada. As a result of anthropogenic desiccation, the lake has decreased in volume by 75% since the 1880s. The hypolimnion of the lake, now too small to meet the oxygen demand exerted by decaying matter, rapidly goes anoxic after thermal stratification. Field and laboratory studies were conducted to examine the feasibility of using oxygenation to avoid hypolimnetic anoxia and subsequent accumulation of ammonia in the hypolimnion, and to estimate the required DO capacity of an oxygenation system for the lake. The accumulation of inorganic nitrogen in water overlaying sediment was measured in laboratory chambers under various DO levels. Rates of ammonia accumulation ranged from 16.8 to 23.5 mg-N m^–2 d^–1 in chambers with 0, 2.5 and 4.8 mg L^–1 DO, and ammonia release was not significantly different between treatments. Beggiatoa sp. on the sediment surface of the moderately aerated chambers (2.5 and 4.8 mg L^–1 DO) indicated that oxygen penetration into sediment was minimal. In contrast, ammonia accumulation was reversed in chambers with 10 mg L^–1 DO, where oxygen penetration into sediment stimulated nitrification and denitrification. Ammonia accumulation in anoxic chambers (18.1 and 20.6 mg-N m^–2 d^–1) was similar to ammonia accumulation in the hypolimnion from July through September of 1998 (16.5 mg-N m^–2 d^–1). Areal hypolimnetic oxygen demand averaged 1.2 g O₂ m^–2 d^–1 for 1994–1996 and 1998. Sediment oxygen demand (SOD) determined in experimental chambers averaged approximately 0.14 g O₂ m^–2 d^–1. Continuous water currents at the sediment-water interface of 5–6 cm s^–1 resulted in a substantial increase in SOD (0.38 g O₂ m^–2 d^–1). The recommended oxygen delivery capacity of an oxygenation system, taking into account increased SOD due to mixing in the hypolimnion after system start-up, is 215 Mg d^–1. Experimental results suggest that the system should maintain high levels of DO at the sediment-water interface (10 mg L^–1) to insure adequate oxygen penetration into the sediments, and a subsequent inhibition of ammonia accumulation in the hypolimnion of the lake.     

Effect of Campsurus notatus on NH+4, DOC Fluxes,O2 Uptake and Bacterioplankton Production in Experimental Microcosms with Sediment‐Water Interface of an Amazonian Lake Impacted by Bauxite Tailings

The aim of this study was to evaluate the influence of Campusurus notatus Eaton 1868 (Ephemeroptera: Polimitarciydae) and the impact of bauxite tailings on ammonium (NH₄⁺) and dissolved organic carbon (DOC) fluxes, oxygen uptake and bacterioplankton production in the sediment‐water interface of Lake Batata, a shallow Amazonian floodplain lake. Mesocosms were constructed from natural and impacted areas of Lake Batata, to reproduce the sediment‐water interface. The cores were incubated with 0 to 2,388 ind m^–2 of Campsurus notatus nymphs, and the changes in NH₄⁺, DOC, O₂ concentration and bacterioplankton production in the overlying water column were measured. Ammonium efflux (F = 9.8, p < 0.05, multiple regression) and oxygen uptake (F = 11.8, p < 0.05) showed a significant correlation with the density of C. notatus in the cores with natural sediment. No differences on DOC release were observed in cores with natural or impacted sediment. In the cores incubated with natural sediment and nymphs of C. notatus, a significant increase (Two‐way ANOVA, p < 0.05) in bacterial production (0.44 μg C l^–1 h^–1) was observed after 3 hours of incubation. In cores incubated with sediment impacted by bauxite tailings, there was no difference in bacterial production with and without C. notatus. We conclude that C. notatus is an important bioturbator in Lake Batata, increasing the turnover rate of nitrogen (NH₄⁺) at the sediment‐water interface and bacterial production in cores incubated with natural sediment. It is also clear that bauxite tailings reduce the nutrients turnover rates in impacted regions of Lake Batata and influence bacterial production.     

Active sliding movement of latex beads coated with skeletal muscle myosin onChara actin bundles

Summary Latex beads coated with rabbit skeletal muscle myosin were introduced by intracellular perfusion intoChara cells from which the tonoplasts had been removed. Mg · ATP dependent movement of the beads along files ofChara chloroplast layers was observed. The movement was in opposite directions on the two sides of the indifferent line, indicating that the movement was dependent on the polarity of the actin bundles. This suggests that the unknown factor responsible for generating the motive force for cytoplasmic streaming inChara endoplasm is myosin. The advantages of the present experimental system for studying the sliding mechanism of actomyosin are discussed.Abbreviations APW artificial pond water - ATP adenosine 5-triphosphoric acid - DTT dithiothreitol - EDTA ethylenediamine tetraacetic acid - EGTA ethyleneglycol-bis(-aminoethyl ether)N, N, N, N-tetraacetic acid - HMM heavy meromyosin - LMM light meromyosin - NEM N-ethylmaleimide - PIPES piperazine-N, N- bis(2-ethanesulfonic acid)