Ion and sugar permeabilities of lecithin bilayers: Comparison of curved and planar bilayers

Summary Na⁺ and sugar permeabilities of egg lecithin bilayers were measured using curved bilayers and planar bilayers as represented by single-bilayer vesicles and black lipid films, respectively. The Na⁺ permeability coefficient measured with single-bilayer vesicles at 25°C is (2.1±0.6)×10^–13 cm sec^–1. Because of technical difficulties it has been impossible to measure ionic permeabilities of values lower than about 10^–10 cm sec^–1 in planar (black) lipid bilayers using tracer methods. Thed-glucose andd-fructose permeabilities were measured with both curved and planar bilayers. The permeability coefficients measured with vesicles at 25°C are (0.3±0.2)×10^–10 cm sec^–1 for glucose and (4±1)×10^–10 cm sec^–1 ford-fructose; these are in reasonable agreement with the corresponding values obtained for planar (black) lipid bilayers which are (1.1±0.3)×10^–10 cm sec^–1 ford-glucose and (9.3±0.3)×10^–10 cm sec^–1 ford-fructose, respectively.This paper is dedicated to the memory of Walther Wilbrandt,cuius nomini nullum par elogium.     

Lead dynamics in the forest floor and mineral soil in south-central Ontario

Recent studies have suggested that the residence time of Pb in the forest floor may not be as long as previously thought, and there is concern that the large pulse of atmospheric Pb deposited in the 1960s and early 1970s may move rapidly through mineral soils and eventually contaminate groundwater. In order to assess Pb mobility at a woodland (JMOEC) in south-central Ontario, a stable Pb isotope tracer ²⁰⁷Pb (8 mg m^–2) was added to the forest floor in white pine (Pinus strobus) and sugar maple (Acer saccharum) stands, respectively, and monitored over a 2-year period. Excess ²⁰⁷Pb was rapidly lost from the forest floor. Applying first-order rate coefficients (k) of 0.57 (maple) and 0.32 (pine) obtained from the tracer study, and estimates of Pb deposition in the region, current predicted Pb concentrations in the forest floor are 1.5–3.1 and 2.1–5.8 mg kg^–1 in the maple and pine plots, respectively. These values compare favorably with measured concentrations (corrected for mineral soil contamination) of 3.1–4.3 mg kg^–1 in the maple stand and 2.6–3.6 mg kg^–1 in the pine stand. The response time (1/^k) of Pb in the forest floor at the sugar maple and white pine plots was estimated to be 1.8 and 3.1 years, respectively. The rapid loss of Pb from the forest floor at the JMOEC is much greater than previously reported, and is probably due to the rapid rate of litter turnover that is characteristic of forests with mull-type forest floors. In a survey of 23 forested sites that border the Precambrian Shield in south-central Ontario, Pb concentrations in the forest floor increased exponentially with decreasing soil pH. Lead concentrations in the forest floor at the most acidic survey sites, which exhibited mor-type forest floors, were approximately 10 times higher (80 mg kg^–1) than at the JMOEC, and pollution Pb burdens were up to 25 times greater. Despite the rapid loss of Pb from the forest floor at the JMOEC, the highest pollution Pb concentrations were found in the upper (0–1 cm) mineral soil horizon. Lead concentrations in the upper 30 cm of mineral soil were strongly correlated with organic matter content, indicating that pollution Pb does not move as a pulse down the soil profile, but instead is linked with organic matter distribution, indicating groundwater contamination is unlikely.     

Purification and properties of D-gluconate dehydratase fromAchromobacter

d-Gluconate dehydratase fromAchromobacter, grown ond-gluconate, was purified 100-fold by a procedure involving ammonium sulfate fractionation and preparative acrylamide gel electrophoresis. The purified enzyme appeared to be homogeneous by disc gel electrophoresis. It is an inducible enzyme with an optimal activity in the pH region 8.4–8.8, a Km value of 2.08 × 10^–2 m ford-gluconate and a molecular weight of 270,000 ± 25,000. Only C₅ and C₆ aldonic acids possessing al-threo configuration at C₂ and C₃ are dehydrated. The dehydration products ofd-gluconate,d-xylonate,d-galactonate,d-fuconate andl-arabonate were identified as 2-keto-3-deoxy compounds by specific colour reactions and thin layer chromatography. Onemm Mg^{+ +} is a powerful activator, 0.1 mm Mn^{+ +} activates poorly and EDTA inhibits. Glutatione, dithiothreitol and mercaptoethanol had no effect, althoughp-chloromercuribenzoate (0.01 mm) decreased enzyme activity.We wish to thank Mr D. Dewettinck for skilful technical assistance. The senior author (J.D.L.) is indebted to the Fonds voor Kollektief en Fundamenteel Onderzoek (Belgium) for research and personnel grants. J.K.-M. is indebted to the Belgian government for a travel and study grant.     

Spatial leaf distribution and self-thinning exponent of<Emphasis Type="Italic"> Pinus banksiana</Emphasis> and<Emphasis Type="Italic"> Populus tremuloides</Emphasis>

A hypothesis that the pattern of spatial leaf distribution in forest canopies is numerically related to the exponent of the self-thinning relationship in even-aged monocultures was tested by evaluating the crown fractal dimension of Pinus banksiana (jack pine) and Populus tremuloides (quaking aspen) in Wood Buffalo National Park, Canada. Pure species stands that were considered the most dense for a given mean tree size were measured to establish the empirical self-thinning relationships. The value of the self-thinning exponent was estimated as –1.42 with 95% Confidence Interval (CI) (–1.47, –1.36) for Pinus banksiana, and –1.29 with 95% CI (–1.45, –1.14) for Populus tremuloides. For each species the box dimension of spatial leaf distribution was estimated from unit cylinders described by sequentially lowering in forest canopies, horizontal flaps of one of various diameters attached to the top of a height-measuring pole. The box dimension appeared as 1.95 (1.84, 2.06) for Pinus banksiana, and 2.24 (2.05, 2.43) for Populus tremuloides. By assuming that the box dimension is equivalent to the fractal dimension at the inter-population level, the self-thinning exponent was predicted to be –1.53 (–1.62, –1.45) for Pinus banksiana, and –1.33 (–1.45, –1.23) for Populus tremuloides. The empirical exponent was equivalent to that predicted from the box fractal dimension, as judged by the 95% CI of the dimensions. We conclude that spatial patterns of leaf distribution in forest canopies, as being characterized by the box fractal dimension, are closely related to the value of the self-thinning exponent in the dense monocultures of the species we examined.     

Correlation between extracellular polysaccharide composition and nodulating ability inRhizobium trifolii

Summary Two auxotrophic mutants ofRhizobium trifolii which are deficient in nodulating ability have been isolated. Both mutants (strain RS 164 His^– and strain RS213 Leu^–) appear to synthesize abnormal extracellular polysaccharides as compared with the wild type strain RS 55. Simultaneous recovery of nodulating ability and wild type polysaccharide composition has been found in a Leu⁺ revertant of strain RS 213.Abbreviation EPS Extracellular Polysaccharide - NIG N-Methyl-N-Nitro-N-Nitrosoguanidine     

The dynamics of old-growth Pseudotsuga forests in the western Cascade Range,Oregon, USA

Size and age structure, spatial analysis, and disturbance history were used to analyse the population structures and regeneration patterns of 8 conifer stands in the central western Cascade Range, Oregon, USA. Variation in forest structure reflected the effects of frequent (20–50 yr) low-intensity fires and treefalls, infrequent (100–200 yr) localised, intense fires, and extensive fires that resulted in stand replacement (every ca 400 yr?).The amount of canopy removed and the size of openings formed by fires and treefalls were important determinants of subsequent forest establishment. Single or several species stands of Pseudotsuga and/or Abies procera, or mixed species stands of Pseudotsuga, Abies procera, Tsuga heterophylla and Abies amabilis established in openings where intense fires had removed most of the canopy trees over several ha. Multi-tiered and multi-aged stands, often containing 400–500 yr-old Pseudotsuga and variously-sized more or less even-aged patches of younger shade tolerant Tsuga heterophylla and/or Abies amabilis, occurred where lower-intensity fires did not kill all overstorey trees or where treefalls occurred after the initial fire.Current regeneration processes are influenced by overstorey composition, the availability and size of canopy openings, and the availability of substrates suitable for regeneration. Tsuga heterophylla and Abies amabilis established under Pseudotsuga menziesii and Abies procera canopies and in small canopy openings (<400 m²) created by windfalls, but rarely under Tsuga. Down logs and stumps were favoured establishment sites for Tsuga.The disturbance regime of fires of low-to moderate-intensity, windfalls, and occasional fires that result in extensive stand replacement contrasts with the pattern of infrequent, catastrophic disturbances proposed for other areas of the Pacific Northwest. Although fires at stand establishment commonly determine much of the composition, structure, and subsequent stand development, canopy replacement by shade tolerant species occurs as the different life histories of the species are expressed in response to various disturbances differing in intensity and frequency. Such a non-equilibrium view of vegetation change is consistent with many other fire-dominated forests of the western United States.     

黑龙江省温带森林火灾碳排放的计量估算

森林火灾干扰作为森林生态系统重要的干扰因子,剧烈地改变着森林生态系统的结构、功能、格局与过程,对区域乃至全球的碳循环与碳平衡产生重要影响。随着全球气候变暖,森林火灾干扰的频率和强度进一步加剧,其排放的含碳气体对大气中温室气体浓度的贡献率更大,进而加快气候变暖的速率。科学有效地对森林火灾碳排放及含碳气体排放量进行计量估算,对了解区域乃至全球的碳循环及碳平衡具有重要的理论价值和实践意义。根据黑龙江省温带森林1953—2012年火灾统计资料和森林调查数据,结合地理信息系统GIS技术,通过野外火烧迹地调查以及实验室的控制环境实验来确定森林火灾碳排放计量中的各种参数,在林分水平上,利用排放因子的方法,估算了黑龙江省温带森林60年间火灾碳排放量和含碳气体排放量。结果表明:黑龙江省温带森林60年间火灾碳排放量为5.88×107t,年均排放量为9.80×105t,约占全国年均森林火灾碳排放量的8.66%;含碳气体CO2、CO、CH4和非甲烷烃(nonmethane hydrocarbons,NMHC)的排放量分别为1.89×108、1.06×107、6.33×105和4.43×105t,含碳气体CO2、CO、CH4和NMHC的年均排放量分别为3.15×106、1.77×105、1.05×104和7.38×103t,分别占全国年均森林火灾各含碳气体排放量的7.74%、6.52%、9.42%和6.53%。研究发现针阔混交林型的森林火灾面积占总过火林地面积的57.54%,由于其燃烧效率较低,在森林火灾中的碳排放量仅占排放总量的38.57%;尤其是针阔混交林森林火灾面积占总过火林地面积的20.71%,而碳排放量仅占总排放量的9.67%;且CO2的排放因子较低,其CO2排放量仅占总排放量的8.95%。同时研究表明,黑龙江省温带森林年均的碳排放对该区域的碳循环与碳平衡产生重要影响,并针对研究结果提出了应对气候变化的森林经营可持续管理策略,亦提出了科学的林火管理策略及其合理化的林火管理路径。     

Assessing the impact of ancient Maya animal use

Tropical forest animals are at high risk worldwide as a result of over-exploitation and forest clearing. Zooarchaeological studies of animal use by the ancient Maya of the southern lowland regions of Guatemala, Honduras, Belize, and Mexico provide long-term historical information on animal populations under conditions of human population growth and climatic change that is valuable to both archaeology and conservation biology. In this paper, zooarchaeological data from 35 chronologically defined faunal sub-samples recovered from 25 ancient Maya archaeological sites are used to assess the effects of ancient hunting on animal populations of the Maya region between the Preclassic and Colonial periods (2000 BC–AD 1697). The variations in species abundance are used as a proxy for describing changes in ancient Maya hunting practices and hunted animal populations, interpreted on the basis of hunting efficiency models from foraging ecology. A significant reduction in the proportion of large mammals, particularly Odocoileus virginianus, in zooarchaeological assemblages between the Late Classic (AD 600–850) and Terminal Classic/Postclassic periods (AD 850–1519) suggest that over-hunting during the Late Classic may have led to a reduction in availability of these animals to the ancient Maya hunters in the later periods. This finding is discussed in relation to important social and environmental variations to evaluate the impact of hunting and other factors such as forest clearance and climate on ancient animal populations in the Maya region.     

Leaching of nitrate and ammonium in heathland and forest ecosystems in Northwest Germany under the influence of enhanced nitrogen deposition

To study the impact of high atmospheric nitrogen deposition on the leaching of NO₃^– and NH₄⁺ beneath forest and heathland vegetation, investigations were carried out in adjacent forest and heathland ecosystems in Northwest Germany. The study area is subjected to high deposition of nitrogen ranging from 15.9 kg ha^–1 yr^–1 in bulk precipitation to 65.3 kg ha^–1 yr^–1 beneath a stand of Pinus sylvestris L. with NH₄–N accounting for 70–80% of the nitrogen deposited. Considerable leaching of nitrogen compounds from the upper horizons of the soil, mostly as nitrate, occurred at most of the forest sites and below a mixed stand of Calluna vulgaris (L.) Hull. and Erica tetralix, but was low in a Betula pubescens Ehrh. swamp forest as well as beneath Erica tetralix L. wet heath and heath dominated by Molinia caerulea(L.) Moench. Ground water concentrations of both NO₃–N and NH₄–N did not exceed 1 mg L^–1 at most of the sites investigated.     

Evidence for differentiation of NK1+ cells into cytotoxic T cells during acute rejection of allogeneic bone marrow grafts

The ability of lethally irradiated C57BL/6 mice to acutely reject H-2^d bone marrow is due to a lymphocyte population that is NK1⁺, ASGM1⁺, CD4^–, CD8^–, CD3⁺. Transfer of spleen cells from C57BL/6 mice expressing these antigens into nonresponder 129 mice adoptively transfers the ability to reject H-2^d marrow grafts. The specificity of this rejection maps to the H-2D major histocompatibility complex (MHC) region. Transplantation of high doses of H-2^d marrow into C57BL/6 overrides the acute rejection mechanism leading to graft survival. During growth of the graft, a cytolytic activity develops that is due to ASGM1⁺, CD8⁺ cytolytic T lymphocytes (CTLs) with H-2L^d specificity. The possibility that the ASGM1⁺, CD8⁺ CTLs are descendents of the CD3⁺, NK1⁺, ASGM1⁺, CD8^– cells responsible for acute rejection is investigated by adoptive cell transfer experiments. We show that beige mice that lack NK1⁺ cells as well as the ability to acutely reject H-2^d marrow fail to generate specific CTLs after transplantation with a high dose of H-2^d marrow. Transfer of highly purified NK1⁺ cells from B6.PL-Ly-2 ^a /Ly-3 ^a (Lyt-2.1) into beige mice together with H-2^d marrow leads to generation of Lyt-2.1 CTLs from donor NK1⁺ cells. These results show that specific CTLs are generated from NK1⁺ cells during acute marrow graft rejection. Offprint requests to: G. Dennert.     

Comparison of soil nitrogen mineralization and nitrification in a mixed grassland and forested ecosystem in central Taiwan

We used the buried bag incubation method to study temporal patterns of net N mineralization and net nitrification in soils at Ta-Ta-Chia forest in central Taiwan. The site included a grassland zone, (dominant vegetation consists of Yushania niitakayamensis and Miscanthus transmorrisonensis Hayata) and a forest zone (Tsuga chinensis var. formosana and Yushania niitakamensis). In the grassland, soil concentration NH₄ ⁺ in the organic horizon (0.1–0.2 m) ranged from 1.0 to 12.4 mg N kg^–1 soil and that of NO₃ ^– varied from 0.2 to 2.1 mg N kg^–1 soil. In the forest zone, NH₄ ⁺ concentration was between 2.8 and 25.0 mg N kg^–1 soil and NO₃ ^–varied from 0.2 to 1.3 mg N kg^–1 soil. There were lower soil NH₄ ⁺ concentrations during the summer than other seasons. Net N mineralization was higher during the summer while net nitrification rates did not show a distinct seasonal pattern. In the grassland, net N mineralization and net nitrification rates were between –0.1 and 0.24 and from –0.04 to 0.04 mg N kg^–1 soil day^–1, respectively. In the forest zone, net N mineralization rates were between –0.03 and 0.45 mg N kg^–1 soil day^–1 and net nitrification rates were between –0.01 and 0.03 mg N kg^–1 soil day^–1. These differences likely result from differing vegetation communities (C₃ versus C₄ plant type) and soil characteristics.     

Effect of riparian land use on contributions of terrestrial invertebrates to streams

Since terrestrial invertebrates are often consumed by stream fishes, land-use practices that influence the input of terrestrial invertebrates to streams are predicted to have consequences for fish production. We studied the effect of riparian land-use regime on terrestrial invertebrate inputs by estimating the biomass, abundance and taxonomic richness of terrestrial invertebrate drift from 15 streams draining catchments with three different riparian land-use regimes and vegetation types: intensive grazing — exotic pasture grasses (4 streams), extensive grazing — native tussock grasses (6 streams), reserve — native forest (5 streams). Terrestrial invertebrate drift was sampled from replicated stream reaches enclosed by two 1 mm mesh drift nets that spanned the entire channel. The mean biomass of terrestrial invertebrates that entered tussock grassland (12 mg ash-free dry mass m^–2 d^–1) and forest streams (6 mg AFDM m^–2 d^–1) was not significantly different (p > 0.05). However, biomass estimated for tussock grassland and forest streams was significantly higher than biomass that entered pasture streams (1 mg AFDM m^–2 d^–1). Mean abundance and richness of drifting terrestrial invertebrates was not significantly different among land-use types. Winged insects contributed more biomass than wingless invertebrates to both pasture and tussock grassland streams. Winged and wingless invertebrates contributed equally to biomass entering forest streams. Land use was a useful variable explaining landscape-level patterns of terrestrial invertebrate input for New Zealand streams. Evidence from this study suggests that riparian land-use regime will have important influences on the availability of terrestrial invertebrates to stream fishes.     

Nitrogen metabolism by heterotrophic bacterial assemblages in Antarctic coastal waters

Field studies to examine the in situ assimilation and production of ammonium (NH₄ ⁺) by bacterial assemblages were conducted in the northern Gerlache Strait region of the Antarctic Peninsula. Short term incubations of surface waters containing ¹⁵N-NH₄ ⁺ as a tracer showed the bacterial population taking up 0.041–0.128 g-atoms Nl^–1d^–1, which was 8–25% of total NH₄ ⁺ uptake rates. The large bacterial uptake of NH₄ ⁺ occurred even at low bacterial abundance during a rich phytoplankton bloom. Estimates of bacterial production using ³H-leucine and -adenine were l.0gCl^–1 d^–1 before the bloom and 16.2 g Cl^–1 d^–1 at the bloom peak. After converting bacterial carbon production to an estimate of nitrogen demand, NH₄ ⁺ was found to supply 35–60% of bacterial nitrogen requirements. Bacterial nitrogen demand was also supported by dissolved organic nitrogen, generally in the form of amino acids. It was estimated, however, that 20–50% of the total amino acids taken up were mineralized to NH₄ ⁺. Bacterial production of NH₄ ⁺ was occurring simultaneously to its uptake and contributed 27–55% of total regenerated NH₄ ⁺ in surface waters. Using a variety of ¹⁵N-labelled amino acids it was found that the bacteria metabolized each amino acid differently. With their large mineralization of amino acids and their relatively low sinking rates, bacteria appear to be responsible for a large portion of organic matter recycling in the upper surface waters of the coastal Antarctic ecosystem.     

Some meteorological conditions associated with forest fires in Galicia (Spain)

The present paper offers data on the effect of certain meteorological parameters on the outbreak of forest fires in Galicia (Spain). In a day-to-day analysis, the values of the stability of the air column and the saturation deficit at the lower levels are related to the number of fires occurring in the following 24 h.     

Biomass and production of Argyrodiaptomus furcatus,a tropical calanoid copepod in Broa Reservoir,southern Brazil

The biomass and the production of Argyrodiaptomus furcatus (Sars), the most abundant copepod in Broa Reservoir (São Carlos, São Paulo State), were estimated, determining in the laboratory the development time and the quantity of organic carbon and establishing the relationship between these two parameters. The daily production was calculated from P = B(1- e^gt) and the annual production was obtained by integrating daily production against time. The maximum production of Argyrodiaptomus furcatus in the reservoir depends on the region considered and on the period of the year. The maximum production was 45.15 mg C m^–3d^–1 in March, 1976 at station II, region of macrophytes and 6.74 mg C m^–3d^–1 at station IV, near the dam. The mean production for the year is 6.26 mg C m^–3d^–1 at station II and 1.43 mg C m^–3d^–1 at station IV.     

Nitrate reductase activity and growth response of forest species to ammonium and nitrate sources of nitrogen

Summary Three tree species,Eucalyptus regnans (F. Muell.),E. obliqua (L'Herit.),Pinus radiata (D. Don) were grown in sand culture with different proportions of nitrate and ammonium. Nitrate Reductase Activity (NRA) was induced in root tissue of all species and in leaf tissue of the eucalypts. An increasing proportion of nitrate resulted in increasing NRA in all species and hence NRA alone is no indication of N-preference. The highest NRA was found withE. regnans, a result which has also been obtained in the mature forest. The growth ofE. regnans was least with NH₄ ⁺ alone, whereas that ofE. obliqua was least with NO₃ ^– alone. The soils of matureE. regnans forest have a high potential for nitrification while those ofE. obliqua forest show little nitrification. Thus the preference for particular N sources shown by seedlings in culture is supported by related properties of mature forests. It is postulated however, that the inducibility of a high level of RNA in seedlings is more likely a result of a preference for NO₃ ^– than a cause.     

Fluff deposition on intertidal sediments: effects on benthic biota, ammonium fluxes and nitrification rates

The effects of fluff deposit on benthic biota,NH₄ ⁺ fluxes and nitrification was studied in thelaboratory using waterlogged and reflooded intertidal sediments fromMarennes-Oléron Bay, France. The fluff deposit was enriched inNH₄ ⁺ compared to underlying sediments, and promotedchanges of the sediment pH, E_h, C:N ratio, C:chla ratio and the NH₄ ⁺ efflux tooverlying water. Statistical analysis showed that pore waterNH₄ ⁺ concentrations were strongly influenced byinteractions between fluff, drying, depth and bioturbation. The fluff depositresulted in anoxia in the top sediments and moved the nitrification zone tosurface layers in fluff. However, the NH₄ ⁺ enrichment influff did not significantly change actual nitrification rates (range 0–1mmol m^–2 d^–1) or potentialnitrification rates (range 3–11 mmolNO₃ ^– m^–2d^–1).     

Structure,biomass and production of a resprouted holm-oak (Quercus ilex L.) forest in NE Spain

When considered as a compartment of nutrients (biomass) and as a flux between compartments (production) vegetation plays an important role in the biogeochemical forest research that is carried out at the Prades research station in two adjacent catchments: L'Avic (51.6 ha) and La Teula (38.5 ha). The forest density at the Prades site, considering both the tree and shrub layers, is 9182 stems ha^–1, with 4527 stems ha^–1 being the tree layer. The predominant species is Quercus ilex with Arbutus unedo and Phillyrea media less common. The structure of the population, estimated by grouping the numbers of the stems in classes of 2.5 cm, shows a distribution which conforms, in both catchments, to a negative exponential equation following the Yoda law. The distribution observed at different altitudes shows great heterogeneity, the number of stems of Q. ilex increases with altitude, from 4000 stems ha^–1 at 800 m, to 14000 stems ha^–1 at 1000 m of altitude. The upper and the lower parts of the watershed show differences in forest production that explain this variation. In this paper the influence of human activities and physical factors on the origin of this structure is discussed. The tree and shrub biomass was calculated by applying allometric regressions for the three predominant species and has been estimated as 113.2 t ha^–1. The tree layer accounts for 92%. Net production was calculated from annual increases (by differences between the 1981 and 1986 basal area measures) of the woody part and the litterfall. The above-ground net production was about 6.5 t ha^–1 year^–1, 95.4% of it being from trees and shrubs and only 4.6% from grasses.     

Purification and partial characterization of ad(−)-lactate dehydrogenase fromDesulfovibrio desulfuricans (ATCC 7757)

Summary A membrane-boundd(–)-lactate dehydrogenase (LDH), an important enzyme in carbon and energy metabolism in sulfate-reducing bacteria of the genusDesulfovibrio, was solubilized from the membrane fraction ofDesulfovibrio desulfuricans (ATCC 7757). The enzyme was purified 84-fold to a final specific activity of 525 nmol DCPIP-reduced/min/mg protein by ammonium sulfate precipitation, chloroform extraction, gel filtration with Sephadex G-150, and hydrophobic column chromatography withN-octylamine Sepharose 4B. The enzyme eluted off a Sephacryl S-300 column as a single peak with a molecular weight of 400 000±40 000 Da. Denaturing gel electrophoresis showed it to be composed of 5 protein bands. The oxidized and dithionite reduced spectra of LDH resembles the spectra ofc-type cytochromes found inDesulfovibrio species. The addition of lactate to LDH resulted in a partially reduced spectrum. The flavin/cytochromec/non-heme iron content per 400 000 Da LDH molecular weight was found to be 11.64.5. The LDH activity was specific ford(–)-lactate and had aK _m ford(–)-lactate of 4.3×10^–4 M. The pH optimum was between 6.5 and 8.5.