Mineralization of Surfactants by Microbiota of Aquatic Plants

The biodegradation of linear alkylbenzene sulfonate (LAS) and linear alcohol ethoxylate (LAE) by the microbiota associated with duckweed (Lemna minor) and the roots of cattail (Typha latifolia) was investigated. Plants were obtained from a pristine pond and a pond receiving wastewater from a rural laundromat. Cattail roots and duckweed plants were incubated in vessels containing sterile water amended with [¹⁴C]LAS, [¹⁴C]LAE, or ¹⁴C-labeled mixed amino acids (MAA). Evolution of ¹⁴CO₂ was determined over time. The microbiota of cattail roots from both ponds mineralized LAS, LAE, and MAA without lag periods, and the rates and extents of mineralization were not significantly affected by the source of the plants. Mineralization of LAS and LAE was more rapid in the rhizosphere than in nearby root-free sediments, which exhibited differences as a function of pond. The microbiota of duckweed readily mineralized LAE and MAA but not LAS. The rate and extent of mineralization were not affected by the source of the duckweed.     

Prokaryotic metabolic activity and community structure in Antarctic continental shelf sediments

The prokaryote community activity and structural characteristics within marine sediment sampled across a continental shelf area located off eastern Antarctica (66 degrees S, 143 degrees E; depth range, 709 to 964 m) were studied. Correlations were found between microbial biomass and aminopeptidase and chitinase rates, which were used as proxies for microbial activity. Biomass and activity were maximal within the 0- to 3-cm depth range and declined rapidly with sediment depths below 5 cm. Most-probable-number counting using a dilute carbohydrate-containing medium recovered 1.7 to 3.8% of the sediment total bacterial count, with mostly facultatively anaerobic psychrophiles cultured. The median optimal growth temperature for the sediment isolates was 15 degrees C. Many of the isolates identified belonged to genera characteristic of deep-sea habitats, although most appear to be novel species. Phospholipid fatty acid (PLFA) and isoprenoid glycerol dialkyl glycerol tetraether analyses indicated that the samples contained lipid components typical of marine sediments, with profiles varying little between samples at the same depth; however, significant differences in PLFA profiles were found between depths of 0 to 1 cm and 13 to 15 cm, reflecting the presence of a different microbial community. Denaturing gradient gel electrophoresis (DGGE) analysis of amplified bacterial 16S rRNA genes revealed that between samples and across sediment core depths of 1 to 4 cm, the community structure appeared homogenous; however, principal-component analysis of DGGE patterns revealed that at greater sediment depths, successional shifts in community structure were evident. Sequencing of DGGE bands and rRNA probe hybridization analysis revealed that the major community members belonged to delta proteobacteria, putative sulfide oxidizers of the gamma proteobacteria, Flavobacteria, Planctomycetales, and Archaea. rRNA hybridization analyses also indicated that these groups were present at similar levels in the top layer across the shelf region.     

Prokaryotic Metabolic Activity and Community Structure in Antarctic Continental Shelf Sediments

The prokaryote community activity and structural characteristics within marine sediment sampled across a continental shelf area located off eastern Antarctica (66°S, 143°E; depth range, 709 to 964 m) were studied. Correlations were found between microbial biomass and aminopeptidase and chitinase rates, which were used as proxies for microbial activity. Biomass and activity were maximal within the 0- to 3-cm depth range and declined rapidly with sediment depths below 5 cm. Most-probable-number counting using a dilute carbohydrate-containing medium recovered 1.7 to 3.8% of the sediment total bacterial count, with mostly facultatively anaerobic psychrophiles cultured. The median optimal growth temperature for the sediment isolates was 15°C. Many of the isolates identified belonged to genera characteristic of deep-sea habitats, although most appear to be novel species. Phospholipid fatty acid (PLFA) and isoprenoid glycerol dialkyl glycerol tetraether analyses indicated that the samples contained lipid components typical of marine sediments, with profiles varying little between samples at the same depth; however, significant differences in PLFA profiles were found between depths of 0 to 1 cm and 13 to 15 cm, reflecting the presence of a different microbial community. Denaturing gradient gel electrophoresis (DGGE) analysis of amplified bacterial 16S rRNA genes revealed that between samples and across sediment core depths of 1 to 4 cm, the community structure appeared homogenous; however, principal-component analysis of DGGE patterns revealed that at greater sediment depths, successional shifts in community structure were evident. Sequencing of DGGE bands and rRNA probe hybridization analysis revealed that the major community members belonged to delta proteobacteria, putative sulfide oxidizers of the gamma proteobacteria, Flavobacteria, Planctomycetales, and Archaea. rRNA hybridization analyses also indicated that these groups were present at similar levels in the top layer across the shelf region.     

Microbial Communities in High and Low Recharge Environments: Implications for Microbial Transport in the Vadose Zone

Abstract Microbial communities along vertical transects in the unsaturated zone were evaluated at five sites in the Pasco Basin, in southeastern Washington State. Sites with contrasting recharge rates were chosen to maximize or minimize the potential for microbial transport. Pore water ages along the vertical transects were established using natural chloride tracers, and ranged from modern to either ∼15,000 yBP (years before present) or ∼30,000 yBP at the two low-recharge sites. Unsaturated flow processes were short-circuited by preferential flow at two of the three high-recharge sites, resulting in rapid movement of water through the vertical transects. Microbial numbers and biomass, based on plate counts, and phospholipid fatty acid (PLFA) concentrations decreased with depth at all sites. The majority (55–90%) of the culturable chemoheterotrophs recovered from most samples were streptomycete bacteria. 16S rRNA gene sequence and MIDI analyses indicated that 75% of the remaining isolates were Gram-positive bacteria (most likely species of Arthrobacter and Bacillus) 25% were Gram-negative bacteria (probably members of several genera in the alpha- and gamma-Proteobacteria). Comparison of microbial communities at low-recharge sites vs. high-recharge sites, where preferential flow occurs, revealed several differences that might be attributed to vertical transport of microbial cells at the high-recharge sites. Plate counts and PLFA analyses indicated that the proportion of streptomycetes, which were abundant at the surface but present in the subsurface as spores, decreased, or remained constant, with depth at the low-recharge sites, but increased with depth at the high-recharge sites. PLFA analyses also indicated that Gram-negative bacteria displayed increased nutrient stress with depth at the high-recharge sites characterized by preferential flow, but not at the low recharge site. This may be a result of advective transport of microbes to depths where it was difficult for them to compete effectively with the established community. Moreover, PLFA community structure profiles fluctuated considerably with depth at the low-recharge sites, but not at the high-recharge sites. This might be expected if transport were distributing the microbial community along the vertical profile at the high-recharge sites. In contrast to the high-recharge sites at which preferential flow occurs, filtration likely prevented vertical transport of microorganisms at the high-recharge site that was characterized by unsaturated flow. Received: 6 November 1996; Accepted: 9 May 1997     

Application of thymol and iprodione to control garlic white rot (Sclerotium cepivorum) and its effect on soil microbial communities

The effect of different dosages of thymol alone, iprodione alone and combinations of thymol and iprodione on white rot disease of garlic and its impact on soil microbial community structure were investigated under greenhouse conditions. Thymol alone or in combination with the fungicide iprodione did not appear to reduce either white rot incidence or soil sclerotia density as compared to an infected control. However, iprodione alone or in combination with thymol reduced soil fungal biomass. In addition, iprodione alone decreased soil microbial activity as estimated by fluorescein diacetate (FDA). Soil bacterial community structure as estimated by phospholipid fatty acid (PLFA) profiles was also was affected by both thymol and iprodione applications. The correlation biplot of the individual PLFAs and biocide treatment indicated that the treatments with thymol alone increased cyclopropyl fatty acid (cy17:0 and cy19:0), while the treatments with iprodione alone increased some saturated and branched fatty acids (principally i16:0, a15:0 and 18:0). In addition, taking into account PLFA biomarkers, thymol applications reduced Gram-negative bacteria in soil. To our knowledge, this research is the first report about the effect of a monoterpene (thymol) on soil microflora.     

Antithrombic activity of N(alpha)-lauroyl-L-arginine ethyl ester (LAE) and 9-fluorenylmethoxycarbonyl-L-arginine methyl ester (Fmoc-L-Arg-OMe)

Simple synthetic compounds of lauroyl-arginine ethyl ester (LAE) and 9-fluorenylmethoxycarbonyl-L-agrinine methyl ester (Fmoc-Arg-OMe) were studied for their inhibitory effect on the hydrolysis of chromogenic substrate Tos-Gly-Pro-Arg-pNA (Chromozym TH) by thrombin with K(i) for LAE 1.92 microM and 77 microM for Fmoc Arg-OMe. It was shown that LAE inhibits thrombin activity almost 20 times more strongly than trypsin (K(i) = 18.9 microM). At the same time LAE preserves the ability to be hydrolyzed by thrombin at pH 8.5 (k(cat) = 3.6 c(-1)) and trypsin (k(cat) = 56 c(-1)). It is suggested, that LAE ability to suppress growth of some microorganisms is conditioned to some extent by its ability to inhibit the activity of trypsin-like serine proteases, participating in the infection process.     

Anaerobic biodegradation of linear alkylbenzene sulfonate (LAS) in upflow anaerobic sludge blanket (UASB) reactors

The anaerobic biodegradation of Linear Alkylbenzene Sulfonate (LAS) was studied in Upflow Anaerobic Sludge Blanket Reactors (UASB). One reactor was fed with easily degradable substrates and commercial LAS solution during a period of 3 months (Reactor 1), meanwhile a second reactor was fed with a commercial LAS solution without co-substrate (Reactor 2) during 4 months. Both reactors were operated with an organic loading rate of 4–5 mg-LAS/l*day and a hydraulic retention time of one day.The LAS biodegradation was determined by full mass balance. LAS was analysed by HPLC in the liquid phase (influent and effluent streams of the reactors) as well as in the solid phase (granular sludge used as biomass). The results indicate a high level of removal (primary biodegradation: 64–85%). Biodegradation was higher in the absence of external co-substrates than in the presence of additional sources of carbon. This indicates that the surfactant can be partially used as carbon and energy source by anaerobic bacteria. Under the operating conditions used, inhibition of the methanogenic activity or any other negative effects on the biomass due to the presence of LAS were not observed. The methanogenic activity remained high and stable throughout the experiment.     

Fluorescein Diacetate Hydrolysis as a Measure of Fungal Biomass in Soil

The fatty acid methyl esters of lipids extracted from an agricultural soil in the preharvest period of soybean or middle growth cycle from wheat were characterized and quantified by gas-liquid chromatography. The fatty acids 18:2ω6 and 16:1ω5 were used as markers of saprotrophic and arbuscular mycorrhizal fungi. In parallel, biomass estimation through plate counts in selective media for cellulolytic and saprotrophic fungi was also performed all throughout a soybean crop or middle growth cycle of wheat. As an enzymatic method, the fluorescein diacetate (FDA) hydrolytic activity of the samples was determined. Owing to the high relationship exhibited by FDA hydrolysis with organic carbon and total nitrogen content of soil, the enzymatic activity was correlated with the microbial biomass estimated through marker lipids or plate counts. The results obtained point out that FDA hydrolysis may be used as a rapid, cheap, and reliable estimator of fungal biomass. Received: 3 August 2000 / Accepted: 13 October 2000     

Deep,subsurface microflora after excavation respiration and biomass and its potential role in degradation of fossil organic matter

Three types of Miocene claystones (amorphous, lamellar, and transitional) were aseptically sampled from depths of 30 m and 150 m below the soil surface. Respiration of these sediments was measured under conditions that prevented inoculation by other microorganisms not indigenous to the claystones in situ. Microbial respiration was higher in lamellar than amorphous claystones and was not affected by sampling depth. During cultivation, microbial biomass (as indicated by PLFA) significantly increased. Microbial biomass after cultivation was significantly higher in sediments from 30 m than from 150 m depth. Both microbial respiration and biomass increased after glucose addition.     

Phospholipid fatty acid composition of microorganisms in pine forest soils of Central Siberia

The phospholipid fatty acid (PLFA) composition of microorganisms in podzolic soils of pine forests was studied in Central Siberia. The live microbial biomass in the 1-m mineral soil layer was found to gradually decrease with depth. Although the biomass decreased by half in the lower horizons, its content remained sufficiently high (12–14 nmol FAs/g soil). The coefficient of similarity in the fatty acid composition between the soils of forest and open (unforested) sites was 0.85. The coefficient of fatty acid richness in the mineral soil layer decreased with depth, while differences in fatty acid profiles increased.     

氮肥添加对高寒藏嵩草(Kobresia tibetica)沼泽化草甸和土壤微生物群落的影响

以藏嵩草沼泽化草甸为研究对象,利用磷脂脂肪酸(PLFA)技术,研究连续6年N素添加对地上植被群落数量特征、土壤微生物群落结构的影响。结果表明:①藏嵩草沼泽化草甸群落生物量、枯枝落叶对施肥处理无明显响应,且莎草科植物对土壤氮素的吸收和利用率较低。②施肥增加了0-10 cm土壤微生物类群PLFAs丰富度尤其细菌和革兰氏阳性菌PLFAs,降低了10-20 cm PLFAs丰富度;③磷脂脂肪酸饱和脂肪酸/单烯不饱和脂肪酸、细菌PLFAs/真菌PLFAs的比值随土壤层次增加而增加;④0-10 cm土层革兰氏阳性菌、真菌PLFAs含量与pH、土壤速效磷、速效氮、土壤有机质显著正相关(P0.05或P0.01);10-20 cm土层,细菌、革兰氏阳性菌、真菌和总PLFAs含量与土壤有机质含量显著正相关(P0.05或P0.01)。表明藏嵩草沼泽化草甸微生物PLFAs含量和丰富度对施肥的响应存在明显的土层梯度效应,土壤微生物PLFAs含量和丰富度主要受表层土壤初始养分含量的影响。     

Algal respiration and the regulation of phytoplankton biomass in a polymictic tropical lake (Lake Xolotlán,Nicaragua)

Community respiration in tropical Lake Xolotlán, Nicaragua, was assessed seasonally and during diurnal cycles, via oxygen consumption in bottle enclosures. Results were analysed in relation to phytoplankton biomass, mixing depth, depth of photic zone and phytoplankton production. A great part of community respiration was associated with the heterotrophic activity of the phytoplankton biomass or its degradation by bacteria and 80% of the variability in oxygen consumption was explained by the variation of chlorophyll-a. Specific rate of respiration was 1.5 mg O2 mg Chla-1 h-1 during diurnal cycles, which corresponded to less than 5% of the specific rate at optimum depth of production. Still, diurnal water column respiratory losses were always of the same magnitude as the total photosynthetic gains in the photic zone, since the mixing depth exceeded the depth of the photic zone. Total column net growth was zero at a ratio between depth of photic zone and mixing depth of 0.19. Water level variations however altered the mixing depth and affected this ratio and net growth. As a consequence, the phytoplankton biomass either increased or decreased until the ratio was re-established through changes of the photic zone depth, which was governed by the phytoplankton biomass itself through the chlorophyll-a light attenuation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Abundance and Activity of Methanotrophic Bacteria in Littoral and Profundal Sediments of Lake Constance (Germany)

The abundances and activities of aerobic methane-oxidizing bacteria (MOB) were compared in depth profiles of littoral and profundal sediments of Lake Constance, Germany. Abundances were determined by quantitative PCR (qPCR) targeting the pmoA gene and by fluorescence in situ hybridization (FISH), and data were compared to methane oxidation rates calculated from high-resolution concentration profiles. qPCR using type I MOB-specific pmoA primers indicated that type I MOB represented a major proportion in both sediments at all depths. FISH indicated that in both sediments, type I MOB outnumbered type II MOB at least fourfold. Results obtained with both techniques indicated that in the littoral sediment, the highest numbers of methanotrophs were found at a depth of 2 to 3 cm, corresponding to the zone of highest methane oxidation activity, although no oxygen could be detected in this zone. In the profundal sediment, highest methane oxidation activities were found at a depth of 1 to 2 cm, while MOB abundance decreased gradually with sediment depth. In both sediments, MOB were also present at high numbers in deeper sediment layers where no methane oxidation activity could be observed.     

The effect of ultraviolet radiation on photosynthesis and ultraviolet-absorbing substances in the endemic Arctic macroalga Devaleraea ramentacea (Rhodophyta)

In field studies conducted at the Kongsfjord (Spitsbergen), the effect of filtered natural radiation conditions (solar without ulraviolet [UV]-A+UV-B, solar without UV-B, solar) on photosynthesis and the metabolism of UV-absorbing mycosporine-like amino acids (MAAs) in the marine red alga Devaleraea ramentacea have been studied. While solar treatment without UV-A+UV-B did not affect photosynthesis during the course of a day, solar without UV-B and the full solar spectrum led to a strong inhibition. However, after offset of the various radiation conditions, all algae fully recovered. Isolates collected from different depths were exposed in the laboratory to artificial fluence rates of photosynthetic active radiation (PAR), PAR+UV-A, and PAR+UV-A+UV-B. The photosynthetic capacity was affected in accordance with the original sampling depth, i.e. shallow-water isolates were more resistant than algae from deeper waters, indicating that D. ramentacea is able to acclimate to changes in irradiance. Seven different UV-absorbing MAAs were detected in this alga, namely mycosporine-glycine, shinorine, porphyra-334, palythine, asterina-330, palythinol, and palythene. The total amount of MAAs continuously decreased with increasing collecting depth when sampled in mid June, and algae taken in late August from the same depths contained on average 30–45% higher MAA concentrations, indicating a seasonal effect as well. The presence of increasing MAA contents with decreasing depth correlated with a more insensitive photosynthetic capacity under both UV-A and UV-B treatments. Populations of D. ramentacea collected from 1 m depth, with one fully exposed to solar radiation and the other growing protected as understorey vegetation underneath the kelp Laminaria saccharina, exhibited quantitatively different MAA compositions in the apices. The exposed seaweeds contained 2.5-fold higher MAA values compared with the more shaded algae. Moreover, the exposed isolates showed a strong tissue gradient in MAAs, pigments, and proteins. The green apices contained 5-fold higher MAA contents than the red bases. Transplantation of D. ramentacea from 2 m depth to the surface induced the formation and accumulation of MAAs after 1 week exposure to the full solar spectrum. Control samples which were treated with the solar spectrum without UV-A+B or with solar without UV-B showed unchanged MAA contents, indicating a strong UV-B effect on MAA metabolism. All data well supported the suggested physiological function of MAAs as natural UV sunscreens in macroalgae.     

Comparison of Whole-Cell Fatty Acid (MIDI) or Phospholipid Fatty Acid (PLFA) Extractants as Biomarkers to Profile Soil Microbial Communities

The whole-cell lipid extraction to profile microbial communities on soils using fatty acid (FA) biomarkers is commonly done with the two extractants associated with the phospholipid fatty acid (PLFA) or Microbial IDentification Inc. (MIDI) methods. These extractants have very different chemistry and lipid separation procedures, but often shown a similar ability to discriminate soils from various management and vegetation systems. However, the mechanism and the chemistry of the exact suite of FAs extracted by these two methods are poorly understood. Therefore, the objective was to qualitatively and quantitatively compare the MIDI and PLFA microbial profiling methods for detecting microbial community shifts due to soil type or management. Twenty-nine soil samples were collected from a wide range of soil types across Oregon and extracted FAs by each method were analyzed by gas chromatography (GC) and GC-mass spectrometry. Unlike PLFA profiles, which were highly related to microbial FAs, the overall MIDI-FA profiles were highly related to the plant-derived FAs. Plant-associated compounds were quantitatively related to particulate organic matter (POM) and qualitatively related to the standing vegetation at sampling. These FAs were negatively correlated to respiration rate normalized to POM (Resp_POM), which increased in systems under more intensive management. A strong negative correlation was found between MIDI-FA to PLFA ratios and total organic carbon (TOC). When the reagents used in MIDI procedure were tested for the limited recovery of MIDI-FAs from soil with high organic matter, the recovery of MIDI-FA microbial signatures sharply decreased with increasing ratios of soil to extractant. Hence, the MIDI method should be used with great caution for interpreting changes in FA profiles due to shifts in microbial communities.     

The impact of crop plant cultivation and peat amendment on soil microbial activity and structure

A rapid means for restoring soil fertility could be addition of peat to the plough layer. The impact of cultivation of eight different crops (the joint impact of plant and the management tailored for each plant), with and without soil amendment by peat treatment on soil microbiological, physical and chemical properties was assessed for two consecutive growing seasons. As a measure of the functional diversity of soil microbial community we estimated the activity of several different extracellular soil enzymes using the ZymProfiler® test kit. ATP content was measured to yield information on the amount of the active microbial biomass, and phospholipid fatty acid (PLFA) profiles were analysed to reveal the microbial community structure. The enzyme activity patterns of the soil samples indicated several differences due to the different crops and years but ATP content and PLFA profiles were rather stable. However, microbial biomass as total amount of PLFAs depended on the plant and peat treatment and ATP content varied between the years. The effects of the peat treatments were less clearly indicated by the biological parameters one or two years after the amendment, as only arylsulphatase and β-xylosidase activities were affected in both the years. Soil moisture, affecting enzyme activities, depended on the year and crop plant and peat addition increased it. Abbreviations: AMC – 7-amino-4-methylcoumarin; AP – aminopeptidase; ATP – adenosine triphosphate; C_mic– microbial biomass carbon; DNA – deoxyribonucleic acid; EC – electrical conductivity; FAME – fatty acid methyl ester; fw – fresh weight; MUF – 4-methylumbelliferyl; na – not added; N_mic– microbial biomass nitrogen; PDE – phosphodiesterase; PLFA – phospholipid fatty acid; PME – phosphomonoesterase; SOM – soil organic matter     

Determinants of Soil Microbial Communities: Effects of Agricultural Management, Season, and Soil Type on Phospholipid Fatty Acid Profiles

Abstract Phospholipid fatty acid (PLFA) profiles were measured in soils from organic, low-input, and conventional farming systems that are part of the long term Sustainable Agriculture Farming Systems (SAFS) Project. The farming systems differ in whether their source of fertilizer is mineral or organic, and in whether a winter cover crop is grown. Sustained increases in microbial biomass resulting from high organic matter inputs have been observed in the organic and low-input systems. PLFA profiles were compared to ascertain whether previously observed changes in biomass were accompanied by a change in the composition of the microbial community. In addition, the relative importance of environmental variables on PLFA profiles was determined. Redundancy analysis ordination showed that PLFA profiles from organic and conventional systems were significantly different from April to July. On ordination plots, PLFA profiles from the low-input system fell between organic and conventional systems on most sample dates. A group of fatty acids (i14:0, a15:0, 16:1ω7c, 16:1ω5c, 14:0, and 18:2ω6c) was enriched in the organic plots throughout the sampling period, and another group (10Me16:0, 2OH 16:1 and 10Me17:0) was consistently lower in relative abundance in the organic system. In addition, another group (15:0, a17:0, i16:0, 17:0, and 10Me18:0) was enriched over the short term in the organic plots after compost incorporation. The relative importance of various environmental variables in governing the composition of microbial communities could be ranked in the order: soil type > time > specific farming operation (e.g., cover crop incorporation or sidedressing with mineral fertilizer) > management system > spatial variation in the field. Measures of the microbial community and soil properties (including microbial biomass carbon and nitrogen, substrate induced respiration, basal respiration, potentially mineralizable nitrogen, soil nitrate and ammonium, and soil moisture) were seldom associated with the variation in the PLFA profiles. Received: 3 February 1997; Accepted: 7 August 1997     

Distribution and activity of microorganisms in subsurface sediments of a pristine study site in Oklahoma

Distribution and activity of microorganisms in surface soil and subsurface sediments were studied in depth profiles of six different microbial biomass and activity indicators (total direct counts, number of cells capable of electron transport system activity, viable cell plate counts, most Probable numbers of protozoa, and 4-hydroxybenzoate-degrading microorganisms, and ATP content). The profiles showed the same general trends on two different dates (January and June 1985). Seasonal variations were noted, but they were not extreme. Biomass and activity values declined sharply with depth in the unsaturated zone, reaching minima in a clay confining layer in the interface zone between 3 and 4 m. Contiguous 10-cm samples from the interface zone showed significant textural and microbiological variability. Higher and more stable biomass and activity values were detected in the saturated zone, the highest being a very permeable gravelly loamy sand layer at approximately 7.5 m. In this layer, viable counts were nearly equal to total counts and they approached the viable counts in surface soil. Surface-type protozoa and cyanobacteria also were detected in this layer, suggesting that it was connected hydrologically to a nearby river. Lowest values were detected in an underlying bedrock clay layer at 8 m, which, despite its impermeability and low viable counts, did contain measurable total counts, 4-hydroxybenzoate-degrading microorganisms, and ATP. Correlations were noted between sediment texture and microbial activity (i.e., sandy texture=high activity, clayey texture=low activity), but other hydrogeological and geochemical factors probably also influenced microbial distribution and activity in the profile.     

Formation of metabolites during biodegradation of linear alkylbenzene sulfonate in an upflow anaerobic sludge bed reactor under thermophilic conditions.

Biodegradation of linear alkylbenzene sulfonate (LAS) was shown in an upflow anaerobic sludge blanket reactor under thermophilic conditions. The reactor was inoculated with granular biomass and fed with a synthetic medium and 3 micromol/L of a mixture of LAS with alkylchain length of 10 to 13 carbon atoms. The reactor was operated with a hydraulic retention time of 12 h with effluent recirculation in an effluent to influent ratio of 5 to 1. A sterile reactor operated in parallel revealed that sorption to sludge particles initially accounted for a major LAS removal. After 8 days of reactor operation, the removal of LAS in the reactor inoculated with active granular biomass exceeded the removal in the sterile reactor inoculated with sterile granular biomass. The effect of sorption ceased after 185 to 555 h depending on the LAS homologs. 40% of the LAS was biodegraded, and the removal rate was 0.5 x 10(-6) mol/h/mL granular biomass. Acidified effluent from the reactor was subjected to dichloromethane extraction followed by gas chromatography/mass spectrometry. Benzenesulfonic acid and benzaldehyde were detected in the reactor effluent from the reactor with active granular biomass but not in the sterile and unamended reactor effluent. Benzenesulfonic acid and benzaldehyde are the first identified degradation products in the anaerobic degradation of LAS.     

Phototrophic plankton of siderotrophic meromictic Lake Kuznechikha (Republic Mari El,Russia)

During summer thermal stratification, a broad transition zone with hypoxic conditions is formed in meromictic ferruginous Lake Kuznechikha between the thermocline and the main gradient of water mineralization. In this zone, the chemical composition of water undergoes an ecologically significant transformation due to overlapping gradients of nutrient concentrations and redox conditions. We present an analysis of a strongly vertically structured community of prokaryotic and eukaryotic phototrophs developing in the lake as a whole and especially in the transition zone. In early summer 2009, a sequence of phototrophic organisms with depth in order Chlorophyceae → Chromatiales → Chloroflexales → Euglenales → Chlorobiales was observed in the transition zone, while cyanobacteria were almost completely absent. Biomass maximum of anoxygenic phototrophic bacteria was located between the peaks of phototrophic picoplankton and euglenoids. Such a coexistence of oxygenic and anoxygenic phototrophs in a wide range of depths is highly unusual and sharply distinguishes Lake Kuznechikha from waterbodies with sulphide-containing monimolimnion.