Antiadhesion and antibiofilm activities of high molecular weight coffee components against Streptococcus mutans

In previous studies we demonstrated that green and roasted coffee contains low molecular weight (LMW) compounds capable of inhibiting the ability of Streptococcus mutans, the major causative agent of human dental caries, to adhere to hydroxyapatite (HA) beads. This study addressed the ability of the whole high molecular weight coffee fraction (cHMW) and of its melanoidin and non-melanoidin components (GFC1-5), applied at concentrations that occur in coffee beverages, to (i) inhibit S. mutans growth; (ii) affect S. mutans sucrose-dependent adhesion to and detachment from saliva-coated HA beads (sHA); and (iii) inhibit biofilm development on microtiter plates. The results indicated that only cHMW is endowed with antimicrobial activity. The cHMW fraction and each of the five GFC components inhibited S. mutans adhesion, the strongest effect being exerted by cHMW (91%) and GFC1 (88%). S. mutans detachment from sHA was four times greater (～20%) with cHMW and the GFC1 and GFC4 melanoidins than with controls. Finally, biofilm production by S. mutans was completely abolished by cHMW and was reduced by 20% by the melanoidin components GFC2 and GFC4 and by the non-melanoidin component GFC5 compared with controls. Altogether these findings show that coffee beverage contains both LMW compounds and HMW melanoidin and non-melanoidin components with a strong ability to interfere in vitro with the S. mutans traits relevant for cariogenesis.     

Antiadhesive effect of green and roasted coffee on Streptococcus mutans' adhesive properties on saliva-coated hydroxyapatite beads

Green and roasted coffees of the two most used species, Coffea arabica and Coffea robusta, several commercial coffee samples, and known coffee components were analyzed for their ability to interfere with Streptococcus mutans' sucrose-independent adsorption to saliva-coated hydroxyapatite (HA) beads. All coffee solutions showed high antiadhesive properties. The inhibition of S. mutans' adsorption to HA beads was observed both when coffee was present in the adsorption mixture and when it was used to pretreat the beads, suggesting that coffee active molecules may adsorb to a host surface, preventing the tooth receptor from interacting with any bacterial adhesions. Among the known tested coffee components, trigonelline and nicotinic and chlorogenic acids have been shown to be very active. Dialysis separation of roasted coffee components also showed that a coffee component fraction with 1000 Da < MW < 3500 Da, commonly considered as low MW coffee melanoidins, may sensibly contribute to the roasted coffee's antiadhesive properties. The obtained results showed that all coffee solutions have antiadhesive properties, which are due to both naturally occurring and roasting-induced molecules.     

Inhibitory effects of apple polyphenols and related compounds on cariogenic factors of mutans streptococci

The inhibitory effects of apple polyphenols (APP) on the synthesis of water-insoluble glucans by glucosyltransferases (GTF) of streptococci of the mutans group and on the sucrose-dependent adherence of the bacterial cells were examined in vitro. APP markedly inhibited the activity of GTF purified from the cariogenic bacterial cells. However, APP showed no significant effect on the growth of the cariogenic bacteria. The strongest GTF inhibitors in APP were apple condensed tannins (ACT), a mixture of procyanidins. The 50% inhibitory doses of ACT against the GTF of S. sobrinus and that of S. mutans were 1.5 microgram/mL and 5 microgram/mL, respectively. The ACT efficacy largely depended upon the degree of polymerization. Interestingly, while the other polyphenols known to inhibit GTF such as tannic acid markedly inhibited salivary alpha-amylase activity, APP and ACT only scarcely inhibited that enzyme activity. This means that APP and ACT might selectively inhibit the bacterial GTF activity under oral conditions.     

Integrative Soil Application of Humic Acid and Sulfur Improves Saline Calcareous Soil Properties and Barley Plant Performance

ABSTRACT

During the 2017 and 2018 seasons, two field experiments were conducted on newly reclaimed saline calcareous soil (7.13 dS m^?1, 16.9% CaCO₃) in the experimental farm of the Faculty of Agriculture, Demo, Fayoum Governorate, Egypt. The current work aimed at identifying the potential positive effects of applied humic acid (HA) and elemental sulfur (S) on some soil properties and barley plant performance. The results showed that the application of HA and/or S at different rates ameliorated the adverse effects of saline calcareous soil conditions and significantly reduced some chemical properties of the soil (e.g., pH, ECe, and CaCO₃%), while soil organic matter (OM%) and some nutrients (e.g., P, Fe, Mn, Cu, and Zn) contents were significantly increased. In addition, the contents of nutrients (e.g., P, Fe, Mn, Cu, and Zn) in barley plant and yielded grain, grain content of N and protein (%), and the performance (e.g., plant height, spike length, grain and straw yields, and weight of 1000-grain) of barley plant were significantly increased with the application of HA and/or S. The best results were obtained through the integrative application of 100 kg HA + 400 kg S ha^?1 to the tested saline calcareous soil. Therefore, the integrative soil application of 100 kg HA + 400 kg S ha^?1 can be recommended for the cultivation and sustainability of crop production in saline calcareous soil, in addition to rationalize the use of mineral fertilizers, which represent a surplus point for the sustainable agriculture system.     

Identification of antiadhesive fraction(s) in nonimmunized egg yolk powder: in vitro study

The presence of antiadhesive component(s) in the hen egg yolk against foodborne pathogens was anticipated from results of a previous animal study conducted by the authors. The previous work showed egg yolk powder without specific antibodies is effective in controlling Salmonella enteritidis,Salmonella typhimurium, and Escherichia coli O157:H7 colonization in laying hens. Therefore, this study was necessary to locate the activity and identify the effective component(s). In vitro experiments were conducted using confluent Caco-2 cell monolayers. S. enteritidis, S. typhimurium, and E. coli O157:H7 were investigated against the various extracted granule and plasma fractions in three different assays: adhesion elimination, adhesion prevention, and antimicrobial. This study revealed original findings and identified the protective yolk fraction against the foodborne pathogens as the granule component, high-density lipoproteins (HDL). The protective activity conveyed by HDL was confirmed to remain intact despite peptic and tryptic enzymatic digestion and to have antiadhesive but not antimicrobial effect.     

Effect of some organic amendments on barley plants under saline condition

Abstract

Enrichment of soils with organic amendments could increase the content of available nutrients, improve soil chemical characteristics and increase plant growth. In the current pots experiment, the influences of biochar (BC), humic acid (HA), and compost (CO) on barely growth were investigated under saline conditions. Barely plants grown on a clay loam soil and irrigated with saline water concentration of (EC?=?13.8 dS m^?1) were amended with BC, HA and CO at a rate of 1 or 3% of soil weight. The results showed that BC, HA and CO treatments had significant effects on the soil salinity, pH, organic matter (SOM), and plant nutrients. The results showed that the high rate application of BC, HA and CO increased the SOM by 14, 75 and 58% respectively, above the control. Consequently, the total chlorophyll as affected by the treatments can be arranged in descending order: BC₃ > CO₁ > CO₃ > HA₃ > HA₁ > BC₁ > C. The high rates of BC, HA and CO increased the dry biomass by 28.0, 21.6 and 39.7% respectively, above the control %, respectively, above the control. The investigated organic amendments increased the nutrients availability and uptake and enhanced the synthesis of chlorophyll in the plant tissues and this may be the reason of increasing the ability of barley to tolerate salinity.     

杉木凋落物及其生物炭对土壤微生物群落结构的影响

以福建建瓯万木林自然保护区内的杉木人工林土壤为研究对象,设置单独添加生物炭、单独添加凋落物以及混合添加凋落物和生物炭处理,进行一年的室内培养实验,研究不同添加物处理对土壤性质及微生物群落结构的影响。结果表明:与对照(S)相比,单独添加凋落物与混合添加凋落物和生物炭均使土壤磷脂脂肪酸(PLFA)总量、真菌丰度以及真菌/细菌比值显著增加;单独添加生物炭与混合添加凋落物和生物炭均使革兰氏阳性细菌/革兰氏阴性细菌比值显著增加。混合添加凋落物和生物炭处理的放线菌丰度显著高于单独添加凋落物处理的。主成分分析表明,不同添加物处理的土壤微生物群落结构存在显著差异;典范对应分析表明,不同添加物处理通过改变土壤p H、全碳、全氮、C/N、可溶性有机碳(DOC)和可溶性有机氮(DON)等性质,进而影响土壤微生物群落结构。     

Plasticity of high and low nutrient‐adapted grasses to added sulfur and nitrogen

Crop and native plants can be characterized as high and low nutrient‐adapted based on their expected response to native and applied nutrients. Our objective was to compare the plasticity of biomass allocation and tissue nutrient concentrations to added sulfur (S) and nitrogen (N) across a continuum of high and low nutrient‐adapted grasses, represented by barley (Hordeum vulgare), smooth brome (Bromus inermis), bluebunch wheatgrass (Pseudoroegneria spicata), and Idaho fescue (Festuca idahoensis). In our greenhouse study, treatments included two S sources (pyrite and gypsum), at 150 and 300 kg S ha^‐1, N at 50 kg ha^‐1, and a check. Shoot biomass of barley, smooth brome, and bluebunch wheatgrass was enhanced by S plus N. Shoot biomass of barley and smooth brome was greater with pyrite than with gypsum. Root biomass of smooth brome and bluebunch wheatgrass was greater with pyrite than with gypsum. Plant S concentrations of barley and Idaho fescue were enhanced by added S. Plant S concentrations in barley and smooth brome were greater with gypsum than with pyrite. Except for barley, plant S pools (shoot biomass x shoot S concentration) were enhanced with S plus N compared with no added nutrients. Nitrogen pools of barley, smooth brome, and bluebunch wheatgrass were higher with pyrite than with gypsum. Soil sulfate (SO₄) was greater when S or S plus N was added than without any added nutrients. For barley and smooth brome, soil sulfate tended to be lower with pyrite than with gypsum. For all soils, pH was lower with added S or added S plus N compared with unamended soils. While pyrite lowered soil pH, gypsum tended to increase soil pH. Overall, barley and smooth brome were highly plastic in responding to enhanced nutrient levels, bluebunch wheatgrass was relatively responsive, and Idaho fescue was least responsive.     

Antibacterial activity of red and white wine against oral streptococci

Wine contains a number of biologically active compounds with beneficial effects on human health. The antibacterial action of commercial red and white wines against oral streptococci responsible for caries development and against S. pyogenes responsible for pharyngitis was studied. Its postcontact effect against S. mutans was also studied. Both wines displayed activity. The compounds responsible for such activities were succinic, malic, lactic, tartaric, citric, and acetic acid. The synthetic mixtures of the organic acids tested at the concentrations found in wine had greater antibacterial activity than the beverages, indicating that in wine they are inhibited by other components. Wine polyphenols displayed no activity against oral streptococci or S. pyogenes. Findings show that wine is active against oral streptococci and S. pyogenes and suggest that it enhances oral health.     

Survival of,and root colonization by,alginate-encapsulated Pseudomonas fluorescens cells following introduction into soil

Summary The survival of Pseudomonas fluorescens cells encapsulated in alginate beads and colonization of wheat roots was studied in soil microcosms inoculated with the cells in alginate beads of varying composition. Cells encapsulated in beads and introduced into a non-sterile loamy sand survived better than cells added directly to the same soil. A recovery/growth step for the bead-encapsulated cells was added before they were introduced into the soil, in an attempt to obtain optimal population levels in the soil. Further, bacterial populations that grew to the highest density in the beads subsequently showed the highest survival levels in soil. The addition of 3% skim milk, or 3% skim milk and 3% bentonite clay to all bead types consistently resulted in the highest survival of the encapsulated cells in soil. Root colonization by P. fluorescens was generally not impaired by the encapsulation in alginate. One week after inoculation into the soil, encapsulated cells in the various bead types were able to colonize the wheat rhizoplane at high population levels, similar to or exceeding those found when free cells were inoculated. In a second root colonization experiment the wheat rhizoplane was also efficiently colonized 7 weeks after the inoculant cells had been introduced into the soil in different bead types. In both assays, the cells encapsulated in beads amended with skim milk plus bentonite clay showed the highest root colonization rates. It is clear, therefore, that alginate-mediated establishment of inoculants can improve inoculant effectiveness.     

Characterization of humic substances derived from swine manure-based compost and correlation of their characteristics with reactivities with heavy metals

Various composts contain a significant amount of humic substances including humic acid (HA) and fulvic acids (FAs). The FA fraction in soils is considered to be sensitive to agronomic and environmental factors. In this study, three fractions of humic substances, HA (MW > 1000 Da), FA (MW > 1000 Da), and FA (MW < 1000 Da) were extracted from swine manure-based compost and characterized, and then, their reactivities were correlated with heavy metals. Compositions of the three fractions of humic substances were characterized by elemental and total acidity analyses and electron spin resonance (ESR), Fourier transform infrared (FTIR), and 13C nuclear magnetic resonance with cross-polarization and magic-angle spinning spectroscopic techniques. Elemental analyses indicated that HA has higher contents of C, H, N, and S than those of FAs. However, FA (MW > 1000) and especially FA (MW < 1000) have higher contents of O than that of HA (MW > 1000). The g values of the ESR spectra of the three fractions showed that the organic free radical characteristics and the widths of the spectra and free radical concentrations of the three fractions are significantly different. The FTIR spectra indicated that HA (MW > 1000) is abundant in C=C bonds while FA (MW > 1000), especially FA (MW < 1000), are abundant in C=O bonds. In addition, 13C NMR spectra indicate that carboxyl contents of FA (MW > 1000), especially FA (MW < 1000), are higher than that of HA (MW > 1000). The sequence of the reactivity in terms of acidic functional groups was FA (MW < 1000) > FA (MW > 1000) > HA (MW > 1000). Elemental and functional group compositions of the three fractions significantly correlated with reported reactivities with heavy metals. The application of swine manure-based compost containing HA and FAs fractions to soil and associated environments may thus significantly affect the concerned reactions with organic and inorganic compounds including pollutants.     

Humic acid and biochar as specific sorbents of pesticides

Purpose

The aim of the research was to compare the effect of two types of organic sorbents—humic acid (HA) and biochar (BC)—in sorption-desorption processes of different polar pesticides, which residues are commonly present in arable soils and are potentially harmful for the environment. It also aims to advance the understanding of behavior of both ionizable and nonionizable pesticides in the presence of BC and HA in soils.

Materials and methods

Three different classes of pesticides were investigated: carbamates (carbaryl and carbofuran), phenoxyacetic acids (2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA)), and aniline derivatives (metolachlor). Investigated humic acid was extracted by Shnitzer’s method from topsoil horizon of arable Gleyic Phaeozem. Biochar was produced from wheat straw in gasification process at 550 °C, remaining 30 s in the reactor. To obtain the experimental goal structural properties of both sorbents were determined and sorption-desorption experiments conducted. To the investigated organic matter samples (HA or BC), 10 or 15 mg L^?1 pesticide solutions in 10 mM CaCl₂ were added and the mixtures were shaken for 24 h. Afterwards, the samples were centrifuged and supernatants analyzed by LC-MS/MS for the pesticide content. Analogous experiment was performed for desorption studies (samples refilled with 10 mM CaCl₂).

Results and discussion

Humic acids exhibited strong affinity for the ionic substances, for which high-percentage uptake (74.6 and 67.9% initial dose of 2,4-D and MCPA, respectively) was obtained. Retention of nonionic carbamates on HA was much weaker (35.4% of carbofuran and 10.2% of carbaryl sorbed). Sorption of carbamates to BC was significantly reduced (76.4–84.3%) by the alkaline hydrolysis. Metolachlor was bound comparably strong both by HA (72.9%) and BC (70.2%), although different mechanisms governed its sorption. Noticeable desorption occurred only in the case of 2,4-D bound to HA (over 50%), whereas other studied compounds were released from HA within the range of 4.4–10.8% of the dose sorbed. Oppositely to HA, desorption of all studied pesticides from BC was completely inhibited, except for 2,4-D (3.7% desorbed).

Conclusions

Investigated humic acid has high affinity to polar, ionic pesticides of high water solubility, which are sorbed via specific interactions with HA functional groups. Studied biochar, due to its moderately hydrophobic character, preferentially attracts nonionic pesticides of relatively high logP values and low water solubility. Hydrophobic bonding is postulated as a main mechanism of their attraction to BC. Besides sorbent structural properties, pH is the main factor governing sorption equilibria in the studied mixtures.

     

Effects of Amendment with Composted Sludge On Soil Humic Acid Properties

The main physical and chemical properties of a composted mixture of sewage sludge and wood chips, the nonamended soil, and soils amended with two rates of the compost, in the presence or absence of barley, were determined. Humic acids (HAs) isolated from these materials were characterized by various methods including elemental analysis and Fourier Transform infrared (FTIR), fluorescence, and electron spin resonance spectroscopies. With respect to the nonamended soil HA, the compost HA was characterized by a prevalent aliphatic character, low oxygenated functional group content, high contents of S, N-containing groups and polysaccharide components, low free radical concentration, high molecular heterogeneity, and low degrees of ring polycondensation, polymerization and humification. Compost application at the low rate appeared to induce only limited modifications in the structural and chemical properties of HAs from amended soils, whereas apparent modifications of HA properties occurred where a high amendment rate was used. The absence or presence of barley cultivation appeared not to exert any measurable effect on the composition and properties of compost-amended soil HAs.     

Model studies on the influence of coffee melanoidins on flavor volatiles of coffee beverages

Addition of the total melanoidin fraction isolated by water extraction from medium-roasted coffee powder to a model solution containing a set of 25 aroma compounds mimicking the aroma of a coffee brew reduced, in particular, the intensity of the roasty, sulfury aroma quality. Model studies performed by static headspace analysis revealed that especially three well-known coffee odorants, that is, 2-furfurylthiol (FFT), 3-methyl-2-butene-1-thiol, and 3-mercapto-3-methylbutyl formate, were significantly reduced in the headspace above an aqueous model solution when melanoidins were added. In particular, the low molecular weight melanoidins (1500-3000 Da) led to the most significant decrease in FFT. In contrast, for example, aldehydes remained unaffected by melanoidin addition.     

Bound amino acids in humic acids from arable cropping systems

We investigated the varying concentrations of bound amino acids in humic acids (HA) extracted from soils under both crop rotation and continuous cropping of rye. The experiment was created in 1957. Since then, winter rye had been grown continuously and also the sequence of the 7 yr rotation had been started: potato, spring barley, alfalfa, alfalfa, oil seed rape, winter rye, and winter rye. Soils were fertilized with NPK and manure. Continuous cropping of rye increased total acidity of soils and the contents of carboxylic and phenolic groups in HA. The total amounts of the bound amino acids in HA from soils under crop rotation were higher than from continuous cropping of rye. Fertilization with NPK increased the contents of bound amino acids more than manure. Neutral amino acids dominated in all samples of HA, and basic amino acids had the lowest concentrations. In both types of cultivation, glutamic acids, glycine, alanine, valine, and lysine dominated. The proline contents in HA from continuous rye cropping were higher than in HA from soils under crop rotation. The concentrations of β‐alanine and lysine were higher in HA from crop rotation indicating a higher microbial biomass since these compounds are typical constituents of bacteria cell walls.     

Glycosylated compounds from okra inhibit adhesion of Helicobacter pylori to human gastric mucosa

In Asian medicine the fruit of the okra plant, Abelmoschus esculentus (L.) Moench., is used as a mucilaginous food additive against gastric irritative and inflammative diseases. To find a rational basis for its use against these diseases, several crude and purified carbohydrate-containing fractions from immature okra fruits were isolated and analyzed, and their effects against Helicobacter pylori in an in situ adhesion model on sections of human gastric mucosa were determined. Pretreatment of the bacteria with a fresh juice preparation inhibited the bacterial adhesion almost completely. Lyophilization and reconstitution of an extract solution led to a reduction of this effect. A crude polysaccharide (RPS) isolated from the fresh juice by ethanolic precipitation showed strong inhibitory effects. Further fractionation of RPS revealed a purified, highly acidic subfraction (AF III) with high antiadhesive qualities. Carbohydrate analysis revealed the presence of rhamnogalacturonans with a considerable amount of glucuronic acid, whereas other inactive subfractions contained little glucuronic acid or were glucuronic acid-free. After heat denaturation of the fresh juice or protein precipitation with 5% TCA the antiadhesive activity of the fresh extract was reduced, indicating that besides polysaccharides, protein fractions also exhibited antiadhesive properties. SDS-PAGE analysis of the precipitate revealed several bands of glycosylated proteins between 25 and 37 kDa that were almost diminished in the nonactive supernatant. Preincubations of gastric tissue with any of the active fractions did not lead to reduced bacterial binding. The antiadhesive activity is therefore due to the blocking capacity of specific Helicobacter surface receptors that coordinate the interaction between host and bacterium. Neither of the active fractions showed inhibitory effects on bacterial growth in vitro. The antiadhesive qualities of okra were assumed to be due to a combination of glycoproteins and highly acidic sugar compounds making up a complex three-dimensional structure that is fully developed only in the fresh juice of the fruit.     

减氮条件下生物炭对甜菜盐碱胁迫的缓解效应

  【目的】  通过模拟盐碱胁迫环境,在施用生物炭、减施氮肥的条件下,研究甜菜根际土壤微生物数量、甜菜氮代谢相关酶活性、块根产量和含糖率的变化,明确生物炭对盐碱胁迫的缓解作用,以及盐碱胁迫下施加生物炭后是否可减少氮肥的施用, 为今后盐碱地改良以及甜菜合理施肥提供理论依据和技术支撑。  【方法】  试验于2018年在黑龙江哈尔滨东北农业大学试验站进行。以甜菜品种KWS0143为试验材料,在土壤中添加盐碱处理以中性盐 (Na₂SO₄、NaCl) 和碱性盐 (Na₂CO₃、NaHCO₃) 模拟盐碱胁迫土壤 (Na+含量为3 g/kg)。采用桶栽试验,每桶装土10 kg,共设6个处理,以在盐碱胁迫土壤施N 180 kg/hm2为对照 (CK),其余5个处理土壤中均加入生物炭30 g/kg, 施氮量依次为N180、162、144、126和108 kg/hm2。子叶完全展开后测定甜菜出苗率,3对真叶后每隔20天左右测定土壤微生物数量及叶片硝酸还原酶 (NR)、谷氨酰胺合成酶 (GS)、谷氨酸合成酶 (GOGAT) 活性,收获后测定块根产量和含糖率并计算产糖量。  【结果】  盐碱胁迫下,施加生物炭显著提高了土壤真菌和细菌数量;BC+N180处理显著提升放线菌数量,在施BC基础上随着施氮量的降低,各时期土壤放线菌含量呈降低趋势。施加生物炭能够显著提高盐碱胁迫下甜菜出苗率,施氮量对出苗率的影响不大;施加生物炭后氮代谢相关酶活性显著提高,其中BC+N162和BC+N144各时期NR活性均高于CK,BC+N144除播种后第117天、第138天外,叶片GS活性均显著高于CK,BC+N144叶片GOGAT活性始终显著高于CK,BC+N126除播种后第53天和第138天外,GOGAT活性显著高于CK;施加生物炭后除BC+N108处理外, 各施加生物炭处理甜菜的块根产量、含糖率、产糖量均显著高于对照,减施氮肥10%～20%的甜菜产量与BC+N180相当,BC+N162的产糖量与BC+N180差异不显著,但显著高于其他处理;而BC+N126和BC+N108的产量与产糖量均显著低于BC+N180。  【结论】  施加生物炭可有效缓解盐碱胁迫对土壤微生物数量及甜菜氮代谢相关酶活性的影响,提高甜菜产量、含糖率、产糖量。在本试验条件下,施加土壤风干质量3%的生物炭,可节约氮肥施用量的10%～20%,提高甜菜的产糖量。     

Microbial biomass growth,following incorporation of biochars produced at 350 °C or 700 °C,in a silty-clay loam soil of high and low pH

Biochar has been widely proposed as a soil amendment, with reports of benefits to soil physical, chemical and biological properties. To quantify the changes in soil microbial biomass and to understand the mechanisms involved, two biochars were prepared at 350 °C (BC350) and 700 °C (BC700) from Miscanthus giganteus, a C4 plant, naturally enriched with ¹³C. The biochars were added to soils of about pH 4 and 8, which were both sampled from a soil pH gradient of the same soil type. Isotopic (¹³C) techniques were used to investigate biochar C availability to the biomass. Scanning Electron Microscopy (SEM) was used to observe the microbial colonization, and Attenuated Total Reflectance (ATR) to highlight structural changes at the surface of the biochars. After 90 days incubation, BC350 significantly increased the biomass C concentration relative to the controls in both the low (p < 0.05) and high pH soil (p < 0.01). It declined between day 90 and 180. The same trend occurred with soil microbial ATP. Overall, biomass C and ATP concentrations were closely correlated over all treatments (R² = 0.87). This indicates that neither the biomass C, nor ATP analyses were affected by the biochars, unless, of course, they were both affected in the same way, which is highly unlikely. About 20% of microbial biomass ¹³C was derived from BC350 after 90 days of incubation in both low and high pH soils. However, less than 2% of biomass ¹³C was derived from BC700 in the high pH soil, showing very low biological availability of BC700. After 90 days of incubation, microbial colonization in the charsphere (defined here as the interface between soil and biochar) was more pronounced with the BC350 in the low pH soil. This was consistent with the biomass C and ATP results. The microbial colonization following biochar addition in our study was mainly attributed to biochar C availability and its large surface area. There was a close linear relationship between ¹³CO₂ evolved and biomass ¹³C, suggesting that biochar mineralization is essentially a biological process. The interactions between non-living and living organic C forms, which are vital in terms of soil fertility and the global C cycle, may be favoured in the charsphere, which has unique properties, distinct from both the internal biochar and the bulk soil.     

Effect of different levels of humic acid on the growth and nutrient uptake of teak seedlings

A greenhouse experiment to study the effect of humic acid (HA) on the growth and nutrient uptake of Teak (Tectona grandis L.f.), a tropical hardwood, was conducted in Ibadan, Nigeria. The plants were grown for four months in top soils (0–30 cm) collected from an Alfisol (high organic matter) and an Oxisol (low organic matter) in Southern Nigeria. Three levels of HA, viz:, 50, 500, and 1000 mg/kg were added to the two soils. The results indicated that HA was beneficial to the growth and nutrient uptake of teak seedlings. Plant monthly growth rates, and height and total dry matter yield increased significantly (p = 0.05) over the controls in the two soils at the three HA application levels. Effects of adding 500 mg/kg and more of HA to the Alfisol were less beneficial while plant parameters and nutrient uptake tended to increase with increasing amounts of HA in the Oxisol. A significant positive correlation was established between rate of HA application and plant height (r = 0.57), stem diameter (r = 0.77) and total dry matter yield (r = 0.67) in the Oxisol, whereas the HA application rate was significantly correlated only with height (r = 0.57) and root/shoot ratio (r = 0.56) in the Alfisol. The addition of HA to the two soils increased the uptake by seedlings of N, P, K, Mg, Ca, Zn, Fe, and Cu, while Mn was decreased.     

Monitoring of fecal indicators in rivers on the basis of random sampling and percentiles

Thermotolerant coliform bacteria and fecal streptococci were monitored in polluted rivers using random sampling and a distribution-free method of estimating percentiles. The objective was to investigate the wide temporal and spatial variation observed earlier in some of these rivers and to monitor for compliance with the standard of acceptable swimming water (1000 thermotolerant coliform bacteria per 100mL). In the summer of 1986 eleven river reaches were visited in random order 3 to 10 times, randomly sampling 2 to 13 sites per reach and visit. Thermotolerant coliform bacteria and fecal streptococci were determined by the membrane filtration technique from 341 and 232 samples, respectively. The results were evaluated on the basis of statistical parameters, percentiles and analysis of variance. Bacterial concentrations varied widely in every reach due to fluctuations of loading and/or hydrological phenomena. During dry periods the bacterial concentrations in rivers were lower than during wet periods. The standard of acceptable swimming water was temporarily exceeded during wet periods but never during dry periods. The use of random sampling and calculation of percentiles was found to provide a good overall picture of the variability of water quality in the rivers. It is recommended to evaluate the bacterial concentrations separately during wet and dry periods.