The effects of phenolic microbial metabolites on the activities of mitochondrial enzymes

The effects of microbial phenolic metabolites on the activities of enzymes of the tricarboxylic acid cycle were investigated in isolated mitochondria. The detection of metabolites of the tricarboxylic acid cycle in the blood of patients with sepsis as potential biomarkers of mitochondrial dysfunction was investigated. We found that microbial phenolic metabolites possess an inhibitory effect on the activity of dehydrogenases, as determined by the reduction of dichlorophenolindophenol and nitroblue tetrazolium in liver mitochondria and liver homogenates. The effect was more pronounced in the case of the oxidation of NAD-dependent substrates than succinate oxidation, as well as at lower concentrations of microbial metabolites than in the case of inhibition of respiration. Using gas chromatography coupled with mass spectrometry it was shown that the content of the tricarboxylic acid cycle metabolites is lower in the blood of patients with sepsis as compared to healthy donors. Our data demonstrate that microbial phenolic acids can significantly contribute to mitochondrial dysfunction and to metabolic suppression, both of which are characteristic of these pathologies.     

The role of thiol antioxidants in restoring mitochondrial functions modified by microbial metabolites

The effects of phenolic acids of microbial origin on mitochondrial functions and the possibility of removing their effects by thiol antioxidants dithiotreitol and N-acetylcysteine were studied. The action of some phenolic acids on the redox state of NADH, the membrane potential and calcium capacity of mitochondria is due to their interaction with thiol groups. Partial restoration of mitochondrial functions occurred in the presence of dithiotreitol and N-acetylcysteine, full recovery (short-term duration) was promoted by the combined action of dithiotreitol and menadione (vitamin K₃). It was found that the protective effect of thiol antioxidants became prooxidant if the medium contained free iron and compounds with quinone structure, capable of entering into a redox cycle with thiols. It is shown that the interaction of thiols with iron and menadione is accompanied by absorption of oxygen to form superoxide anion. Prooxidant effect of thiol antioxidants may explain the absence of the protective effect at the later stages of sepsis and systemic inflammatory syndrome.     

Characterization of Microbial Consortia in Paddy Rice Soil by Phospholipid Analysis

Abstract Microbial biomass and community structure in paddy rice soil during the vegetation period of rice were estimated by analysis of their phospholipid fatty acids (PLFA), hydroxy fatty acids of lipopolysaccharides (LPS-HYFA), and phospholipid ether lipids (PLEL) directly extracted from the soil. A clear change in the composition of the community structure at different sampling periods was observed, indicated by the principal component analysis of the PLFA. A dramatic decline of ester-linked PLFA was observed in the soil samples taken at the second sampling time. In contrast to the ester-linked PLFA, the non-ester-linked PLFA composition did not change. The hydroxy fatty acids of lipopolysaccharides as well as ether lipids decreased consecutively during the observation period. Total microbial abundance was estimated to be (4.1–7.3) × 10⁹ cells g^-1 soil (dry weight). About 44% account for aerobic and 32% for facultative anaerobic bacteria, and 24% for archaea, on average. According to the profile and patterns of PLFA in the soil sample, it may be suggested that the paddy soil at the August sampling period contained more abundant facultative anaerobic bacteria (ca. 36%) and archaea (ca. 37%), but the total microbial biomass was significantly lower than in the remaining sampling periods. As the plant approached maturity, the microbial community structure in the soil changed to contain more abundant Gram-negative bacteria and methanotrophs. Received: 23 September 1999; Accepted: 28 February 2000; Online Publication: 12 May 2000     

Sensitivity to vinyl phenol derivatives produced by phenolic acid decarboxylase activity in Escherichia coli and several food-borne Gram-negative species

Ferulic, p-coumaric, and caffeic acids are phenolic acids present in soil, food, and gut, which have antimicrobial effects. Some Gram (+) bacteria metabolize these phenolic acids into vinyl derivatives due to phenolic acid decarboxylase activity (PAD) involved in the phenolic acid stress response (PASR). In this study, the antimicrobial activity of phenolic acids and their vinyl derivatives was tested on a panel of desirable and undesirable food-borne bacteria, especially Gram (?) species of Salmonella, Enterobacter, Klebsiella, and Pseudomonas, most of them without PAD activity. Native and engineered Escherichia coli strains either expressing or not PAD activity were included. Gram (?) bacteria of the panel were not significantly inhibited by phenolic acids at 3 mM, but were dramatically inhibited by the corresponding vinyl derivatives. On the contrary, Gram (+) bacteria displaying the PASR face the toxicity of phenolic acids by PAD activity and are not inhibited by vinyl phenols. In E. coli, the genes aaeB and marA, encoding efflux pumps for antimicrobial compounds, are upregulated by the addition of p-coumaric acid, but not by its derivative 4-vinyl phenol (p-hydroxystyrene). These results suggest that phenolic acids and their vinyl phenol derivatives produced by PAD (+) species could have a significant impact on undesirable or pathogenic food-borne Gram (?) bacteria in complex microbial ecosystems.     

阿魏酸、对羟基苯甲酸及其混合液对土壤氮及相关微生物的影响

通过室内培养法,研究了不同浓度的阿魏酸、对羟基苯甲酸及其混合液对土壤氮素、与氮素转化相关的微生物和酶的影响。结果表明,10^-4mol/L阿魏酸和对羟基苯甲酸使土壤铵态氮降低了11.18%和10.87%,硝态氮降低了6.33%和3.95%;10^-3mol/L阿魏酸、对羟基苯甲酸及其混合液分别使可溶性有机氮降低了6.59%、10.16%和10.39%。阿魏酸、对羟基苯甲酸及其混合液抑制了氨化细菌、硝化细菌和反硝化细菌的生长,削弱了土壤脲酶与蛋白酶的活性。与对照相比,10^-4mol/L混合液降低了26.04%的氨化细菌、30.79%的硝化细菌和16.74%的反硝化细菌。10^-3mol/L阿魏酸减少了3.33%的土壤脲酶和20.87%的蛋白酶活性;10^-3mol/L对羟基苯甲酸降低了土壤脲酶6.63%,蛋白酶22.94%;10^-3mol/L混合液减少了土壤脲酶7.47%和蛋白酶23.79%。混合液对土壤氮素转化的抑制作用最强,表明阿魏酸和对羟基苯甲酸存在协同作用。阿魏酸和对羟基苯甲酸等酚酸类化合物通过抑制土壤氮素转化微生物及其酶活性,从而影响土壤氮素转化。     

Competition and coexistence of sulfate-reducing bacteria,acetogens and methanogens in a lab-scale anaerobic bioreactor as affected by changing substrate to sulfate ratio

The microbial population structure and function of natural anaerobic communities maintained in lab-scale continuously stirred tank reactors at different lactate to sulfate ratios and in the absence of sulfate were analyzed using an integrated approach of molecular techniques and chemical analysis. The population structure, determined by denaturing gradient gel electrophoresis and by the use of oligonucleotide probes, was linked to the functional changes in the reactors. At the influent lactate to sulfate molar ratio of 0.35 mol mol⁻¹, i.e., electron donor limitation, lactate oxidation was mainly carried out by incompletely oxidizing sulfate-reducing bacteria, which formed 80–85% of the total bacterial population. Desulfomicrobium- and Desulfovibrio-like species were the most abundant sulfate-reducing bacteria. Acetogens and methanogenic Archaea were mostly outcompeted, although less than 2% of an acetogenic population could still be observed at this limiting concentration of lactate. In the near absence of sulfate (i.e., at very high lactate/sulfate ratio), acetogens and methanogenic Archaea were the dominant microbial communities. Acetogenic bacteria represented by Dendrosporobacter quercicolus-like species formed more than 70% of the population, while methanogenic bacteria related to uncultured Archaea comprising about 10–15% of the microbial community. At an influent lactate to sulfate molar ratio of 2 mol mol⁻¹, i.e., under sulfate-limiting conditions, a different metabolic route was followed by the mixed anaerobic community. Apparently, lactate was fermented to acetate and propionate, while the majority of sulfidogenesis and methanogenesis were dependent on these fermentation products. This was consistent with the presence of significant levels (40–45% of total bacteria) of D. quercicolus-like heteroacetogens and a corresponding increase of propionate-oxidizing Desulfobulbus-like sulfate-reducing bacteria (20% of the total bacteria). Methanogenic Archaea accounted for 10% of the total microbial community.     

Propionate Oxidation by and Methanol Inhibition of Anaerobic Ammonium-Oxidizing Bacteria

Anaerobic ammonium oxidation (anammox) is a recently discovered microbial pathway and a cost-effective way to remove ammonium from wastewater. Anammox bacteria have been described as obligate chemolithoautotrophs. However, many chemolithoautotrophs (i.e., nitrifiers) can use organic compounds as a supplementary carbon source. In this study, the effect of organic compounds on anammox bacteria was investigated. It was shown that alcohols inhibited anammox bacteria, while organic acids were converted by them. Methanol was the most potent inhibitor, leading to complete and irreversible loss of activity at concentrations as low as 0.5 mM. Of the organic acids acetate and propionate, propionate was consumed at a higher rate (0.8 nmol min⁻¹ mg of protein⁻¹) by Percoll-purified anammox cells. Glucose, formate, and alanine had no effect on the anammox process. It was shown that propionate was oxidized mainly to CO₂, with nitrate and/or nitrite as the electron acceptor. The anammox bacteria carried out propionate oxidation simultaneously with anaerobic ammonium oxidation. In an anammox enrichment culture fed with propionate for 150 days, the relative amounts of anammox cells and denitrifiers did not change significantly over time, indicating that anammox bacteria could compete successfully with heterotrophic denitrifiers for propionate. In conclusion, this study shows that anammox bacteria have a more versatile metabolism than previously assumed.     

Inhibition of mitoNEET attenuates LPS-induced inflammation and oxidative stress

MitoNEET (mitochondrial protein containing Asn–Glu–Glu–Thr (NEET) sequence) is a 2Fe–2S cluster-containing integral membrane protein that resides in the mitochondrial outer membrane and participates in a redox-sensitive signaling and Fe–S cluster transfer. Thus, mitoNEET is a key regulator of mitochondrial oxidative capacity and iron homeostasis. Moreover, mitochondrial dysfunction and oxidative stress play critical roles in inflammatory diseases such as sepsis. Increased iron levels mediated by mitochondrial dysfunction lead to oxidative damage and generation of reactive oxygen species (ROS). Increasing evidence suggests that targeting mitoNEET to reverse mitochondrial dysfunction deserves further investigation. However, the role of mitoNEET in inflammatory diseases is unknown. Here, we investigated the mechanism of action and function of mitoNEET during lipopolysaccharide (LPS)-induced inflammatory responses in vitro and in vivo. Levels of mitoNEET protein increased during microbial or LPS-induced sepsis. Pharmacological inhibition of mitoNEET using mitoNEET ligand-1 (NL-1) decreased the levels of pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α in animal models of sepsis, as well as LPS-induced inflammatory responses by macrophages in vitro. Inhibition of mitoNEET using NL-1 or mitoNEET shRNA abrogated LPS-induced ROS formation and mitochondrial dysfunction. Furthermore, mitochondrial iron accumulation led to generation of LPS-induced ROS, a process blocked by NL-1 or shRNA. Taken together, these data suggest that mitoNEET could be a key therapeutic molecule that targets mitochondrial dysfunction during inflammatory diseases and sepsis.Subject terms: Mechanisms of disease, Stress signalling, Sepsis, Bacterial infection, Target identification     

连作苹果土壤酚酸对平邑甜茶幼苗的影响

为探讨连作(重茬)苹果土壤中酚酸类物质的积累与苹果连作障碍的关系,在砂培条件下,取连作果园土壤中实际浓度的酚酸类物质处理平邑甜茶幼苗,探讨了连作2a的果园土壤中实测浓度的根皮苷、间苯三酚、根皮素、对羟基苯甲酸和肉桂酸对平邑甜茶幼苗根系线粒体指标、抗氧化酶活性、膜过氧化程度及活性氧(ROS)含量的影响。结果表明:连作土壤中实际浓度的5种酚酸类物质均使平邑甜茶幼苗生长受到抑制,根系受影响程度高于地上部分,表现为根冠比降低;线粒体膜通透性转换孔(MPTP)开放程度增大,线粒体膜电位降低,细胞色素Cyt c/a比值下降;降低了幼苗根系中超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性,增加了过氧化氢(H2O2)、超氧阴离子自由基(O·-2)以及丙二醛(MDA)的含量。土壤浓度的5种酚酸类物质中,以根皮苷处理抑制效果最显著,间苯三酚处理抑制力最小。因此,根皮苷是引起苹果连作障碍的主要酚酸,实践中应重点考虑对根皮苷的降解以缓解苹果连作障碍。     

Microbial activity and community structure in a lake sediment used for psychrophilic anaerobic wastewater treatment

Aims: The aim of the study was to investigate the feasibility of a continuous reactor for psychrophilic anaerobic wastewater treatment by using the sludge from cold natural environment. Methods and Results: Six sludge samples (S1–S6) were collected from different cold natural locations to select sludge with high anaerobic microbial activity under low temperatures. After a 225‐day incubation, the maximum specific methane production rate of a waterfowl lake sediment (S1) at 15°C (70·5 mLCH₄ gVSS^?1 day^?1) was much higher than all other samples. S1 was thus chosen as the seed sludge for the reactor treating synthetic brewery wastewater at 15°C, by immobilizing the micro‐organisms on polyurethane foam carriers. The chemical oxygen demand (COD) removal efficiency reached over 80% after 240‐day operation at an organic loading rate of 5·3 kg m^?3 day^?1, and significant enrichment of biomass was observed. Clone libraries of the microbial communities in the inoculum had high diversities for both archaea and bacteria. Along with a decrease in microbial community diversities, the dominant bacteria (79·5%) at the end of the operation represented the phylum Firmicutes, while the dominant archaeon (41·5%) showed a similarity of 98% with the psychrotolerant methanogen Methanosarcina lacustris. Conclusions: The possibility of using anaerobic micro‐organisms from cold environments in anaerobic wastewater treatment under psychrophilic conditions is supported by these findings. Significance and Impact of the Study: This study enriches the theory on microbial community and the application on anaerobic treatment of sludge from cold natural environments.     

Effects of larval mosquitoes (Aedes triseriatus) and stemflow on microbial community dynamics in container habitats.

The dynamics of the microbial food sources for Aedes triseriatus larvae in microcosms were found to be strongly influenced by larval presence. The total abundance of bacteria in water samples generally increased in response to larvae, including populations of cultivable, facultatively anaerobic bacteria. Additionally, a portion of the community shifted from Pseudomonaceae to Enterobacteriaceae. Bacterial abundance on leaf material was significantly reduced in the presence of actively feeding larvae. Principle-component analysis of whole community fatty acid methyl ester (FAME) profiles showed that larvae changed the microbial community structure in both the water column and the leaf material. Cyclopropyl FAMEs, typically associated with bacteria, were reduced in microcosms containing larvae; however, other bacterial fatty acids showed no consistent response. Long-chain polyunsaturated fatty acids characteristic of microeukaryotes (protozoans and meiofauna) declined in abundance when larvae were present, indicating that larval feeding reduced the densities of these microorganisms. However, presumed fungal lipid markers either increased or were unchanged in response to larvae. Larval presence also affected microbial nitrogen metabolism through modification of the physiochemical conditions or by grazing on populations of bacteria involved in nitrification-denitrification. Stemflow primarily influenced inorganic ion and organic compound concentrations in the microcosms and had less-pronounced effects on microbial community parameters than did larval presence. Stemflow treatments diluted concentrations of all inorganic ions (chloride, sulfate, and ammonium) and organic compounds (total dissolved organic carbon, soluble carbohydrates, and total protein) measured, with the exceptions of nitrite and nitrate. Stemflow addition did not measurably affect larval biomass in the microcosms but did enhance development rates and early emergence patterns of adults.     

Microbial origin of phenylcarboxylic acids in the human body

In previous studies we demonstrated increased amounts of phenylcarboxylic acids (PCA) in serum of patients with sepsis. This observation prompted the present study of the ability of the human microbiome bacteria to produce PCA in vitro. PCA were detected in culture media by gas chromatography-mass spectrometry. Increased amounts of phenyllactic and p-hydroxyphenyllactic acids were produced by Klebsiella pneumonia, Escherichia coli, and Staphylococcus aureus. Certain strict anaerobes (bifidobacteria, lactobacteria, eubacteria) have also been found to actively produce these PCA, but these bacteria are not etiologically linked to sepsis. Thus our results demonstrate the ability of sepsis-related bacteria to produce PCA and provide experimental support for the theory that the accumulation of PCA in the blood of patients with sepsis results from microbial degradation of phenylalanine and tyrosine.     

Effects of Larval Mosquitoes (Aedes triseriatus) and Stemflow on Microbial Community Dynamics in Container Habitats

The dynamics of the microbial food sources for Aedes triseriatus larvae in microcosms were found to be strongly influenced by larval presence. The total abundance of bacteria in water samples generally increased in response to larvae, including populations of cultivable, facultatively anaerobic bacteria. Additionally, a portion of the community shifted from Pseudomonaceae to Enterobacteriaceae. Bacterial abundance on leaf material was significantly reduced in the presence of actively feeding larvae. Principle-component analysis of whole community fatty acid methyl ester (FAME) profiles showed that larvae changed the microbial community structure in both the water column and the leaf material. Cyclopropyl FAMEs, typically associated with bacteria, were reduced in microcosms containing larvae; however, other bacterial fatty acids showed no consistent response. Long-chain polyunsaturated fatty acids characteristic of microeukaryotes (protozoans and meiofauna) declined in abundance when larvae were present, indicating that larval feeding reduced the densities of these microorganisms. However, presumed fungal lipid markers either increased or were unchanged in response to larvae. Larval presence also affected microbial nitrogen metabolism through modification of the physiochemical conditions or by grazing on populations of bacteria involved in nitrification-denitrification. Stemflow primarily influenced inorganic ion and organic compound concentrations in the microcosms and had less-pronounced effects on microbial community parameters than did larval presence. Stemflow treatments diluted concentrations of all inorganic ions (chloride, sulfate, and ammonium) and organic compounds (total dissolved organic carbon, soluble carbohydrates, and total protein) measured, with the exceptions of nitrite and nitrate. Stemflow addition did not measurably affect larval biomass in the microcosms but did enhance development rates and early emergence patterns of adults.     

Fatty acid-membrane interactions in isolated cardiac mitochondria and erythrocytes

The effects of long-chain fatty acids on mitochondrial functions and red cell stability were studied. In albumin-containing incubation media, fatty acid distribution between the albumin-bound and the unbound fraction was estimated by calculation. When fatty acids are compared to one another on the basis of identical unbound concentrations, their effectiveness differs by orders of magnitude. Fatty acids stimulate mitochondrial basic oxygen consumption, thus lowering the respiratory control index, without changing the ATP/O ratio at lower concentrations. Lower concentrations increase Ca²⁺ uptake velocity, but decrease maximal Ca²⁺ storage capacity. The order of effectiveness of different fatty acids is the same for both oxidative phosphorylation and Ca²⁺ uptake. The influence of fatty acids on red cell stability in hypotonic media is similar to these effects both in concentration range and in order of effectiveness. The influence of fatty acids on red cell stability and their critical micellar concentrations were investigated because these are general characteristics of ‘detergent-like’ compounds. Critical micellar concentrations of the fatty acids in physiological salt buffers are, in general, at least 10-fold higher than the concentrations exhibiting membrane effects in vitro. Based on these findings it is suggested that, of the various concentrations reported in literature for myocardial non-esterified fatty acids, only the lowest values are physiologically possible.     

Role of cardiolipin peroxidation and Ca in mitochondrial dysfunction and disease

Cardiolipin is a unique phospholipid which is almost exclusively located at the level of the inner mitochondrial membrane where it is biosynthesized. This phospholipid is known to be intimately involved in several mitochondrial bioenergetic processes. In addition, cardiolipin also has active roles in several of the mitochondrial-dependent steps of apoptosis and in mitochondrial membrane dynamics. Alterations in cardiolipin structure, content and acyl chains composition have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions, including ischemia/reperfusion, different thyroid states, diabetes, aging and heart failure. Cardiolipin is particularly susceptible to ROS attack due to its high content of unsaturated fatty acids. Oxidative damage to cardiolipin would negatively impact the biochemical function of the mitochondrial membranes altering membrane fluidity, ion permeability, structure and function of components of the mitochondrial electron transport chain, resulting in reduced mitochondrial oxidative phosphorylation efficiency and apoptosis. Diseases in which mitochondrial dysfunction has been linked to cardiolipin peroxidation are described. Ca²⁺, particularly at high concentrations, appears to have several negative effects on mitochondrial function, some of these effects being linked to CL peroxidation. Cardiolipin peroxidation has been shown to participate, together with Ca²⁺, in mitochondrial permeability transition. In this review, we provide an overview of the role of CL peroxidation and Ca²⁺ in mitochondrial dysfunction and disease.     

Variation in Microbial Biomass and Community Structure in Sediments of Eutrophic Bays as Determined by Phospholipid Ester-Linked Fatty Acids

The distribution of phospholipid ester-linked fatty acids (PLFA) in sediments of eutrophic bays (Hiroshima Bay and Aki Nada) was studied to quantify the microbial biomass, community structure, and nutritional status. A total of 63 fatty acids in the range of C₁₀ to C₂₄ were determined. They consist of saturated fatty acids, branched fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids, and variation was revealed in the relative proportions of these fatty acids in sediments. On the basis of the PLFA concentration in sediments, the calculated microbial biomass showed variation (mean ± standard deviation = 0.70 × 10⁸ ± 0.53 × 10⁸ cells per g [dry weight] of sediment) in the eutrophic bays. In sediments, a higher amount of biomass was observed in the coastal area of Hiroshima Bay than that observed in the rest of the bay and adjacent Aki Nada. The microbial community structure of the present study area, as characterized by the PLFA profiles, showed very low percentages of polyunsaturated fatty acids and long-chain fatty acids characteristic of microeukary-otes and terrestrial input, respectively, and high percentages of fatty acids characteristic of bacteria. The distribution of PLFA profiles also showed the relative contribution of both aerobic and anaerobic bacteria, especially sulfate-reducing bacteria, in the study area. The relative proportions of PLFA revealed distinctive differences among the stations of the study area, as is evidenced from six clusters obtained for the PLFA profiles. The results of Tukey's honestly significant difference test further confirmed that the sediments in the coastal area of Hiroshima Bay were significantly enriched by a number of fatty acids when compared with other areas investigated where relatively few fatty acids were present in significant quantities. No marked variation in environmental parameters in the surface- and bottom-water samples was observed, indicating the absence of any water movement in the study area. Furthermore, low redox potential and the levels of sulfide in the sediment revealed the reduced condition of the sediment. The existing environmental conditions and pollution of the study area were attributed to the observed microbial community structure in the sediments.     

Archaean metabolic evolution of microbial mats

Microbial mats of coexisting bacteria and archaea date back to the early Archaean: many of the major steps in early evolution probably took place within them. The earliest mats may have formed as biofilms of cooperative chemolithotrophs in hyperthermophile settings, with microbial exploitation of diversifying niches. Anoxygenic photosynthesis using bacteriochlorophyll could have allowed mats, including green gliding bacteria, to colonize anaerobic shallow-water mesothermophile habitats. Exploitation of the Calvin–Benson cycle by purple bacteria allowed diversification of microbial mats, with some organisms in more aerobic habitats, while green sulphur bacteria specialized in anaerobic niches. Cyanobacterial evolution led to more complex mats and plankton, allowing widespread colonization of the globe and the creation of further aerobic habitat. Microbial mat structure may reflect this evolutionary development in broad terms, with anaerobic lower levels occupied by archaeal and bacterial respirers, fermenters and green bacteria, while the higher levels contain aerobic purple bacteria and are dominated by cyanobacteria. A possible origin of eukaryotes is from a fusion of symbiotic partners living across a redox boundary in a mat. The geological record of Archaean mats may be present as isotopic fingerprints: with the presence of cyanobacteria, mats may have had a nearly modern structure as early as 3.5 Ga ago (1 Ga = 10⁹ years).     

Variation in Microbial Community Structure in Two Boreal Peatlands as Determined by Analysis of Phospholipid Fatty Acid Profiles

Analyses of phospholipid fatty acids (PLFAs) were used to assess variation in community structure and total microbial biomass in two boreal peatlands in Sweden. The total PLFA concentration in peat ranged from 0.16 to 7.0 nmol g of wet peat(sup-1) (median, 0.70 nmol g of wet peat(sup-1)). Principal-component analysis of PLFA data revealed that the degree of depth-related variation in PLFA composition was high among peatland habitats, with general differences between wet sites, with water tables within a few centimeters of the moss surface, and dry sites, with water tables >10 cm below the moss surface. However, variation in PLFA composition over the growing season was negligible. In the principal-component analyses, most PLFAs were determined to be parts of clusters of covarying fatty acids, suggesting that they originated in the same functional groups of microorganisms. Major clusters were formed by monounsaturated (typical of gram-negative eubacteria), terminally branched (gram-positive or anaerobic gram-negative eubacteria), methyl-branched and branched unsaturated (sulfate-reducing bacteria and/or actinomycetes), (omega)8 monounsaturated (methane-oxidizing bacteria), and polyunsaturated (eucaryotes) PLFAs. Within the clusters, PLFAs had rather distinct concentration-depth distributions. For example, PLFAs from sulfate-reducing bacteria and/or actinomycetes and those from methane-oxidizing bacteria had maximum concentrations slightly below and at the average water table depth, respectively.     

Remediation of Thiothrix spp. associated bulking problems by raw wastewater feeding: A full-scale experience

An industrial wastewater treatment plant (WWTP) in Australia has long suffered from bulking problems associated with the proliferation of Thiothrix spp. The WWTP consists of a covered anaerobic lagoon (CAL) followed by a sequencing batch reactor (SBR). The CAL functions as both an anaerobic digester and surge lagoon for the irregular flow of wastewater generated from the production of seasonal products. Chemical analysis of the raw influent showed it was composed of a mixture of organic acids, phenols and alcohols. The CAL effluent was characterised by high acetic acid and phenolic concentrations. An attempt was made to manipulate the SBR microbial community to improve settling by direct feeding small volumes of raw influent into the SBR. After raw feeding, the plant ceased bulking as the settled sludge volume reduced from 930 to 200 mL L^?1. 16S rRNA gene profiling and biovolumes of SBR samples revealed major changes in the microbial community. The Thiothrix spp. population decreased from 36.8% to 0.2%, and Zoogloea spp. dominated all samples after raw feeding. Therefore, direct feeding is proposed as a control method for industrial plants with surge/anaerobic lagoons in order to manage the bulking problems caused by Thiothrix spp. in downstream SBRs.     

THE EFFECTS OF TEN PHENOLIC COMPOUNDS ON HYPOCOTYL GROWTH AND MITOCHONDRIAL METABOLISM OF MUNG BEAN

Ten phenolic compounds were examined for their effect on mung bean (Phaseolus aureus L.) hypocotyl growth and on respiration and coupling parameters of isolated mung bean hypocotyl mitochondria. Three compounds—tannic, gentisic, and p-coumaric acids—inhibited hypocotyl growth and when incubated with isolated hypocotyl mitochondria released respiratory control, inhibited respiration, and prevented substrate-supported Ca²⁺ and PO₄ transport. Vanillic acid also inhibited hypocotyl growth and reduced mitochondrial Ca²⁺ uptake but did not affect respiration or respiratory control of isolated mitochondria. This is the first compound reported to selectively inhibit Ca²⁺ uptake in plant mitochondria. Two other phenolic compounds—α, 3,5-resorcylic and protocatechuic acids—showed no significant effect on hypocotyl growth and did not affect mitochondrial oxidative phosphorylation either separately or in various combinations. Four phenolic compounds—ferulic, caffeic, p-hydroxybenzoic, and syringic acids—showed a significant reduction in mung bean hypocotyl growth but did not inhibit any of the mitochondrial processes examined. The results show that phenolic compounds which alter respiration or coupling responses in isolated mitochondria also inhibit hypocotyl growth and may reflect a mechanism of action for these natural growth inhibitors.