Characterization of alkaline phosphatase and organic phosphorous utilization in the oceanic dinoflagellate Pyrocystis noctiluca

Phosphate depleted Pyrocystis noctiluca (Murray) Schuett 1895 has at least one phosphomonoesterase (EC 3:1:3:1) which is triphasic between 0.1 and 222 mol P. The enzyme has a broad temperature range with maximum activity at 50 °C and a Q₁₀ of 1.4 to 1.5. A break in the Arrhenius plot at 35 °C implies the enzyme is membrane-bound. Cytological staining of whole cells and cell fractionation studies (showing 26 times higher specific activity in the particulate compared with the cytoplasmic fraction) suggest the enzyme is plasmalemma-bound. The enzyme has an absolute metal requirement which would be satisfied by Mg⁺⁺ but not Mn⁺⁺, Zn⁺⁺, Fe⁺⁺, or Co⁺⁺ at seawater concentrations. Alkaline phosphatase is a stable enzyme whose activity is not altered by inhibitors of protein synthesis. Orthophosphate inhibition of enzyme activity was largely eliminated in the presence of these inhibitors. Apparently, a protein induced by PO₄ ^3-, rather than PO₄ ^3- itself, inhibits alkaline phosphatase. Cell-free alkaline phosphatase can hydrolyze a variety of phosphate esters and linear polymers of inorganic phosphorus as well as disolved organic phosphorus from tropical oceanic waters. These same hydrolysable organic and inorganic phosphorus compounds support the axenic culture growth of P. noctiluca, suggesting that naturally occurring hydrolysable organic phosphorus compounds may also support the growth of this alga.     

Alkaline phosphatase activity in subtropical Central North Pacific waters using a sensitive fluorometric method

This paper describes a fluorometric method for assaying low levels of the enzyme alkaline phosphatase in seawater. The assay is based on the hydrolysis of the monophosphate ester bond of 3-0-methylfluorescein phosphate. This enzyme is synthesized by many microorganisms when phosphate becomes limiting. Alkaline phosphatase activity was detected in phytoplankton from the nutrient-impoverished surface waters of the subtropical Central North Pacific Ocean. The presence of naturally occurring phosphatase suggests that phosphorus may be limiting to phytoplankton growth in these waters. The phytoplankton in water samples lacking enzyme activity at the time of collection produced phosphatase within 1 to 2 days of incubation at in situ temperatures.     

Decomposition of organic and solubilisation of inorganic phosphorus compounds by bacteria isolated from a marine sandy beach

The ability to decompose organic and to solubilise inorganic phosphorus compounds was studied in heterotrophic bacteria isolated from a sandy beach in Sopot, southern Baltic coast. Bacteria able to hydrolyse DNA and phytin were most numerous, while only a small percentage of the studied strains was able to depolymerise glycerophosphate. The ranking of the potential of the studied bacteria to solubilise metallic phosphate salts as follows: calcium hydrogen phosphate>ferric phosphate>magnesium phosphate>calcium phosphate>aluminium phosphate. There were marked differences in the level of depolymerisation of organic compounds of phosphorus and solubilisation of inorganic phosphorus between bacteria inhabiting different parts of the studied beach, while there were generally no differences between the surface and subsurface sand layers. The activity of alkaline phosphatase was higher than that of acid phosphatase.Communicated by O. Kinne, Oldendorf/Luhe     

桑沟湾海域叶绿素a的时空分布特征及其影响因素研究

2009年4月-2010年2月对山东荣成典型养殖海湾—桑沟湾海域水体中的叶绿素a（Chl-a）进行了6个航次的监测,分析该海区表底层海水中Chl-a的质量现状,探讨Chl-a在桑沟湾海区的时空分布特征,以及与水温和营养盐等主要环境因子的相关性。结果表明,桑沟湾海域表层海水Chl-a质量浓度范围为0.36～9.77μg L-1,平均值为2.17μg L-1;底层海水Chl-a质量浓度范围为0.40～7.46μg L-1,平均值为2.14μg L-1。Chl-a质量浓度的季节性变化呈现一定的模式,夏季〉秋季〉春季〉冬季。Chl-a的质量浓度在春季和冬季呈现由湾内向湾外递减的分布特征,而夏季和秋季则没有明显的分布规律。垂直分布上,夏季表层Chl-a质量浓度高于底层,冬季则是底层高于表层,春秋2季表底层垂直分布比较均匀。相关分析显示桑沟湾Chl-a与水温呈较显著正相关,但与营养盐溶解无机氮（DIN）不具显著意义的相关关系。总体看来,桑沟湾海域Chl-a的时空分布受养殖环境状况、水文环境及陆地径流和外源输入的共同影响,贝藻养殖活动及营养盐的陆源输入是影响Chl-a分布格局的重要因素。     

Photosynthetic carbon acquisition in the red algaGracilaria conferta

Photosynthetic properties of the common red algaGracilaria conferta, collected from the eastern Mediterranean Sea were investigated in 1989, in order to begin evaluating its adaptative strategies with regard to the inorganic carbon composition of seawater, and to test whether the alleged C₄ photosynthesis of anotherGracilaria species is common within the genus. Net photosynthetic rates ofG. conferta were, under ambient conditions of inorganic carbon (ca. 10µM, CO₂ and 2.2 mM HCO ₃ ^- ), not sensitive to O₂ over the range 10 to 300µM, and the CO₂ compensation point was low (ca. 0.005µM). Ribulose-1,5-bisphosphate carboxylase/oxygenase was the major carboxylating enzyme, with a crude extract activity of 175µmol CO₂ g^–1 fresh wt h^–1 while phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase were present at 70 and 20%, respectively, of that activity. No activities of the decarboxylases NAD-and NADP-malic enzyme could be detected. The¹⁴C pulse-chase incorporation pattern showed thatG. conferta fixes inorganic carbon via the photosynthetic carbon reduction cycle only, with no evidence for photosynthetic C₄ acid metabolism. Photosynthesis at the natural seawater pH of 8.2 was, at 25°C and saturating light, saturated at the ambient inorganic carbon concentration of 2.5 mM. It is proposed that, under ambient inorganic carbon conditions, a CO₂ concentrating system other than C₄ metabolism provides an internal CO₂ concentration sufficient to suppress the O₂ effect on ribulose-1,5-bisphosphate carboxylase/oxygenase and, thus, on photorespiration, in a medium where the external free CO₂ concentration is lower than theK _m(CO₂) of the carboxylating enzyme. Since inorganic carbon, under natural saturating light conditions, seems not to be a limiting factor for photosynthesis ofG. conferta, it likely follows that other nutrients limit the growth of this alga in nature.     

流沙湾海水中石油烃的时空分布特征研究

于2008年2月（冬季）、5月（春季）、8月（夏季）和11月（秋季）对流沙湾进行了4次采样考察,研究分析了流沙湾表层海水中石油烃质量浓度的平面分布和季节变化特征。结果表明,在2008年度,流沙湾表层海水石油烃的质量浓度为0~1.930 mg.L-1,平均值为0.080 mg.L-1,季节差异比较明显,呈春、冬、夏、秋季依次减小的变化趋势,冬、春季节海水呈现不同程度石油污染,夏、秋季节属Ⅰ、Ⅱ级水质,整个流沙湾海域表层海水石油烃的平面分布相对比较均匀。在内外湾分布上,冬、春、秋季节外湾大于内湾,而夏季节内湾大于外湾。流沙湾的水产养殖活动是其海水石油烃时空分布的主要影响因素。     

莱州湾近岸海域中典型抗生素与抗性细菌分布特征及其内在相关性

为了揭示海陆衔接区环境中抗生素与抗性细菌分布特征及其内在相关性,以莱州湾及其主要入海河流为研究区域,利用HPLC-MS/MS分析样品中15种磺胺类抗生素(SAs)和6种喹诺酮类抗生素(QNs)的浓度,并通过改良的Method 1604(US EPA)评估海水与沉积物中2种典型水传病原微生物大肠杆菌(E.coli)与金黄色葡萄球菌(S.aureus)的抗生素抗性水平,进而探讨该区域水体中抗性菌株的分布特点以及微生物抗性率与相应抗生素浓度的相关性。结果显示,莱州湾水体与沉积物中普遍存在磺胺与喹诺酮类抗生素残留及抗性污染问题。两大类抗生素在水体中平均残留浓度分别为3.89 ng·L~(-1)(SAs)和234.68ng·L~(-1)(QNs),在沉积物中分别为0.91 ng·g~(-1)(SAs)和49.37 ng·g~(-1)(QNs),且分布特征基本呈现自河流向海洋逐渐递减的趋势,说明河流输入是莱州湾抗生素污染的主要来源。在水体中,具有磺胺类抗性的E.coli和S.aureus平均检出量分别达到2 018和4 683 CFU·L~(-1),抗性率范围分别在0%~37.3%和10.6%~45.8%之间;而2种喹诺酮类抗性病原微生物的平均检出量则相对较低,分别为1 315 CFU·L~(-1)(E.coli)和1 461 CFU·L~(-1)(S.aureus),抗性率分别为0%~50.0%和0%~20.8%;此外,相比于E.coli,S.aureus为沉积物中的主要抗性病原微生物,磺胺与喹诺酮类抗性S.aureus检出率均高于80%,平均检出量分别为24CFU·g~(-1)和18 CFU·g~(-1)。相关性分析表明,莱州湾近岸海域水体中磺胺类抗生素浓度与磺胺类抗性微生物总量之间具有良好的线性关系,然而其与微生物抗性率之间并未表现出相似的规律,说明近岸海洋环境中抗生素的残留量不是影响抗性菌株丰度的唯一因素。     

大鹏湾中溶解态总氮和总磷的多年调查结果分析

依据2000—2010年每月1次的调查资料,简要描述和讨论大鹏湾海水中溶解态总氮（DTN）和溶解态总磷（DTP）质量浓度的空间分布和时间变化。结果表明由于受到香港和深圳陆源排放的影响,DTN和DTP质量浓度在吐露港和沙头角附近水域1年4季都较高。DTN和DTP的平均质量浓度分别为0.21和0.03 mg.L-1,比溶解态无机氮（DIN）和溶解态无机磷（DIP）的高1倍以上,表明大鹏湾海水中溶解态有机氮（DON）和溶解态有机磷（DOP）分别是DTN和DTP的主要赋存形态。平均DTN/DTP原子比〉16,反映了大鹏湾海水中磷可能是海洋浮游生物生长繁殖的限制因素。夏季,由于南海北部陆架低温、高盐和高营养盐底层水潜入湾内,底层DTN和DTP质量浓度明显高于其他季节。11年调查期间,DTN质量浓度的年际变化趋势平稳,DTP质量浓度的年际变化呈较明显的下降趋势,而DTN/DTP原子比的年际变化呈较明显的上升趋势。     

Regulation of soil enzyme activities in constructed wetlands under a short-term drying period

The activities of extracellular enzymes are important in understanding decomposition of soil organic matter in wetlands subjecting to drying. The activity of soil extracellular enzymes (β-glucosidase, N-acetylglucosaminidase, and phosphatase), and related physicochemical parameters were monitored in constructed freshwater wetlands during a one-month drying manipulation. Drying increased redox potential and decreased soil water content significantly (P<0.05). Higher content of soil organic matter (P<0.05) and higher concentrations of inorganic N (nitrate, P<0.01; and ammonia, P<0.001) were also observed significantly under drying condition. Soil hydrolase enzyme activities were stimulated significantly (β-glucosidase, P<0.05; N-acetylglucosaminidase, P<0.01; and phosphatase, P<0.001), and a two-phase pattern of enzyme activities was revealed under drying condition. The increase of soil enzyme activities under drying condition was significantly related to soil redox potential (P<0.001). Drying strongly affected soil enzyme activities only when soil water content remained above an optimal level for enzymatic catalysis (higher than 23% w/w), corresponding to redox potentials below 250–300 mV. Our results suggest that, under drying condition, potential enzyme activities may be regulated by redox potential, in respect to soil moisture, and consequently alter nutrient availability in wetlands.     

有机磷细菌的分离鉴定及其对MC-RR的响应(The Isolation and Identification of Organic Phosphorus Bacteria and Its Response to MC-RR)

从云南滇池水样中分离出具有解磷能力的有机磷细菌P-2,并利用现代分子生物学技术进行了初步鉴定.用0.01、5mg·L-1微囊藻毒素(MC-RR)处理有机磷细菌P-2,研究了MC-RR对其生长、细胞内酸碱磷酸酶活性(ACP和AKP)以及培养液中可溶性磷酸盐含量的影响.结果表明,高浓度MC-RR能显著抑制有机磷细菌的生长,延缓其细胞增殖,抑制细胞内酸碱磷酸酶活性以及培养液中可溶性磷酸盐含量的升高,因而可能改变或减缓生态系统中磷循环的进程,这表明微囊藻毒素在一定程度上可能调节水体细菌功能群落.     

Effects of temperature,seawater osmolality and season on oxygen consumption and osmoregulation of the amphipod Gammarus oceanicus

Seasonal variations of oxygen consumption rate, haemolymph osmolality and the concentrations of the inorganic ions potassium and sodium in the haemolymph were measured in the littoral amphipod Gammarus oceanicus collected from the Trondheimsfjorden, Norway in 1987. For each season comparisons were made of amphipods acclimated for 1 wk to 0.5, 4.5, 10.0, 15.0 and 20.0°C, in combination with seawater osmolalities of 100, 500 and 1200 mOsm and to the seawater osmolality corresponding to that of the collecting site. The oxygen consumption rate showed a temperature insensitivity when the amphipods were acclimated to low temperatures in winter and high temperatures in summer. Significant differences were found in oxygen consumption between individuals acclimated to various medium osmolalities, possibly indicating higher energy requirements for osmotic and ionic regulation at low seawater osmolalities. Oxygen consumption rate was significantly higher in summer than in other seasons. Haemolymph osmolality and the concentration of the inorganic ions sodium and potassium were not influenced by temperature or season. Determination of haemolymph osmolalities and concentrations of inorganic ions revealed that G. oceanicus is a strong hyper-osmotic and hyper-ionic regulator in dilute seawater. The concentration of potassium in the haemolymph is less influenced by seawater osmolality than haemolymph osmolality and the haemolymph concentration of sodium.     

Habitat use by dusky dolphin in patagonia: how predictable is their location?

Off Patagonian coasts, Argentina, the dusky dolphin is one of the most common small cetaceans. This species is the aim of newly developed watching activities during summer in Golfo Nuevo. However, the real occurrence and movement pattern are unknown. The objectives of this work were to investigate the predictability of dusky dolphin distribution, group structure and behaviour in the western portion of Golfo Nuevo, with respect to environmental features (bottom depth, bottom slope, distance from shore and substrate). Random transects in the bay were searched by small boat during the summer and autumn of 2001–2004. When a group of dolphins was sighted, estimates of group size, composition (mothers with calves, adults and juveniles only, and mixed groups) and the predominant activity (feeding, travelling, socialising, resting and milling) were recorded and thereafter at 2 min intervals. A grid of 1.5 × 1.5 km was constructed and each cell was characterised by environmental features, Area Use Index (percent of total annual search effort) and Activity Index (predominant behaviour of groups observed in that cell). Mothers with calves and smaller groups and resting behaviour occurred in shallowest waters supporting the idea/hypothesis that movement to shallower water is related to increased safety for individuals. Travelling occurred in the deepest areas with other behaviours observed in intermediate depths. Dolphin distribution within the bay differed significantly between years, but this was not related to any of the factors analysed in this study. Although there was considerable variation between years, in general, dolphins were found in deeper waters further from shore (except for mother–calf groups) and over areas with steeper seafloor gradient. The high variability in the distribution of the animals does not allow for the generation of a simple, area-specific management plan.     

黄河三角洲不同植被类型土壤酶活性的季节变化

黄河三角洲自然保护区的酶活性季节特征一定程度影响了该地植被分布类型,为研究黄河三角洲自然保护区不同植被土壤酶活性的季节特征,分别选取碱蓬(Suaeda salsa)、柽柳(Tamarix chinensis)、芦苇(Phragmites communis)、刺槐(Black Locust)和高粱(Sorghum)5种典...     

Uptake of inorganic carbon and internal carbon cycling in symbiont-bearing benthonic foraminifera

Incorporation rates of inorganic carbon and its distribution between the organic matter and the skeleton have been measured using ¹⁴C tracer techniques on two species of symbiont-bearing benthonic foraminifera in the Gulf of Elat: Amphistegina lobifera (a perforate species) and Amphisorus hemprichii (an imperforate species). Under constant experimental conditions, incorporation rates of the radiotracer become linear with time after several hours in A. hemprichii and after one day in A. lobifera. A. lobifera showed a lag time of 24 h for skeletal incorporation, whereas in A. hemprichii uptake into the skeleton started within 2 h. Pulse-chase incubations in radioactive seawater, followed by unlabelled incubations, demonstrate transfer of photosynthetically acquired ¹⁴C into the skeleton of A. lobifera. No such transfer was found in A. hemprichii. The total ¹⁴C uptake by A. lobifera increased during the first 24 h of cold chase incubation. This increase suggests the existence of an internal inorganic carbon pool that was lost (probably evaporated) during the analysis of pulse incubations. However, during the following chase incubations, the ¹⁴C in this pool was incorporated mainly into the skeleton and retained during analysis, causing the increase in the total uptake. No such increase was found in A. hemprichii. Additional ¹⁴C uptake experiments on other species of the genera Operculina, Heterostegina and Borelis suggest that the differences in pathways for incorporation of carbon between A. lobifera and A. hemprichii can be generalized to the perforate and imperforate foraminiferal groups. In perforate species, respired carbon originally taken up through photosynthesis is partly recycled into the skeleton. In imperforate species such a transfer has not been demonstrated. Perforate species seem to have a large internal inorganic carbon pool which serves mainly for calcification and possibly also for photosynthesis, while imperforate species may take up carbon for calcification directly from seawater or have a very small inorganic carbon pool.     

Benthic fauna of a shallow-water gaseohydrothermal vent area in the Aegean Sea (Milos, Greece)

The benthic community of shallow-water hydrothermal vents (10 m water depth) in a sandy bay on the south coast of Milos, Greece was studied. The macro- and meiofauna, as well as environmental factors such as temperature, salinity, sulfide concentration, grain size composition, ATP concentration, organic carbon, chlorophyll a and phaeopigments were evaluated. Samples were taken along transects from a seagrass meadow into a hydrothermally active area. Hydrothermally active spots were distinguished from the surrounding sediment by their black sediment coloration and an overlying white bacterial mat. For comparison, a control transect from a seagrass meadow into bare sand in a non-vent area in the same bay was studied. Overall, we found decreasing faunal diversity from the seagrass bed towards the hydrothermally active area. Along this gradient, four different zones could be distinguished. (a) The seagrass area had a relatively low diversity compared to the control stations, but much higher diversity than in the areas directly influenced by hydrothermal activity. (b) The border zone between the seagrass and the hydrothermal area, with moderate sulfide concentrations, pH values, seawater salinity and temperatures, was inhabited by an impoverished community dominated by the polychaete Capitella capitata, the nematodes Oncholaimus campylocercoides and Sabatieria sp., and an as yet undescribed chromadorid nematode (Chromadorina sp.). (c) The transition zone at the border of the hydrothermal area proper, with temperatures and sulfide concentrations higher than in the border zone, was characterized by high salinity (60‰) and low pH values. Along with the gastropod Cyclope neritea, single specimens of C. capitata and O. campylocercoides occurred. (d) The hydrothermal area proper, characterized by high sulfide concentrations, had high sediment temperatures and high salinities. The pH was as low as 6. Here, the gastropod Cyclope neritea was the only species occurring in considerable numbers. The gaseohydrothermal activity seems to largely exclude the surrounding fauna in a graded zonal pattern. The increasing hydrothermal stress entrains a change of the ambient biota towards a depauperate consortium of tolerant, opportunistic species, e.g. Capitella capitata (Polychaeta) and Oncholaimus campylocercoides (Nematoda). Although the hydrothermal area proper was characterized by a thick bacterial mat, the benthic community was characterized not by bacteria feeders but by scavenging species. Received: 13 September 1996 / Accepted: 24 October 1996     

The trophic role of glycolic acid in coastal seawater. II. Seasonal changes in concentration and heterotrophic use in Ipswich Bay,Massachusetts, USA

Glycolic acid is a known algal excretory product which is found in marine waters and is readily metabolized by marine bacteria. The following parameters were measured over the course of a year in Ipswich Bay: chlorophyll a, temperature, viable bacteria, heterotrophic uptake of glycolate, and glycolate concentrations. The latter two were combined to give estimates of the flux of glycolate for a station 3 km out in the bay and for an inshore station. Pronounced seasonal changes were found for all parameters. Statistically significant correlations between heterotrophic V _max and glycolic acid concentrations and temperature were found, but not between planktonic chlorophyll a and any of the other parameters. Measurements of glycolic acid flux yielded an annual flux of 2.84 g m^-2 for the bay station, which is about 0.5% of the bay phytoplankton production. Glycolic acid turns over roughly 12 times per year in the bay. It contributes perhaps as much to bacterial metabolism as any other single substrate, but is apparently not of dominating importance.     

Cytoenzymatic investigation of intracellular digestion in the symbiont-bearing hydrothermal bivalve <Emphasis Type="Italic">Bathymodiolus azoricus</Emphasis>

Invertebrates harbouring endosymbiotic chemoautotrophic bacteria are widely distributed in a variety of reducing marine habitats, including deep-sea hydrothermal vents. Bathymodiolids are dominants of the biomass at geochemically distinct vent sites of the Mid Atlantic Ridge (MAR) and thus are good candidates to study biological processes in response to site-specific conditions. To satisfy their nutritional requirements, these organisms depend to varying extent on two types of chemoautotrophic symbionts and on filterfeeding. The quantitative relationships of the nutritional modes are poorly understood. Using enzyme cytochemistry, electron microscopy and X-ray microanalysis, the structural and functional aspects of the cellular equipment necessary for lysosomal digestion was studied. We provide evidence for the following: (1) the basis of intracellular digestion of symbionts in Bathymodiolus azoricus from two geochemically distinct vent sites was not mainly in the large lysosomal bodies as previously thought (based on the membranous content resembling bacteria); (2) senescent bacteria are autolysed, possibly by bacterial acid phosphatase, that is more likely a cell cycling of the symbionts rather than an active lysosomal digestion by the host; (3) the consistent absence of hydrolases may indicate the improper use of the name “lysosome” for large vesicles at the base of the gill bacteriocytes (4) nutrient transfer in B. azoricus, therefore, may more likely be accomplished through leaking of metabolites from the symbiont to the host, not excluding lysosomal resorption of dead bacteria as an auxiliary strategy for organic molecule transfer; (5) evidence is provided for microvillar transfer of substances from the seawater that may indicate filter-feeding, in non-symbiotic ciliated gill cells of mussels from Lucky Strike; (6) two types of lysosomal vesicles can be distinguished in digestive cells based on their enzymatic content and their elemental composition.     

Effects of organic and inorganic fertilisation on soil nutrient dynamics in a Savannah region (DR Congo)

Very few studies have considered the residual effect of inorganic and organic fertilisation on oxisol chemistry and plant productivity while studying the response of maize to fresh fertiliser application. The purpose of the present study was to examine the effects of five treatments of inorganic and organic fertilisers on maize productivity and soil fertility under field conditions in a Savannah region. The trials were conducted from 2009 to 2011 and the treatments included inorganic nitrogen–phosphorus (NP), Entada abyssinica, Tithonia diversifolia, inorganic NP combined with E. abyssinica, and inorganic NP combined with T. diversifolia, and no fertilised plots. The combination of NP with T. diversifolia or E. abyssinica leaves resulted in the highest increase in grain yields during the first crop season.The positive residual effects of fertilisers on maize grain yield were strong and significant in the immediate succeeding season and decreased during the second year following fertilisation. The highest residual effect was observed in plots fertilised with E. abyssinica combined with NP, followed by T. diversifolia combined with NP, and E. abyssinica and T. diversifolia without NP, respectively. The lowest residual effect was observed in plots fertilised with inorganic NP. Analytical results revealed that total nutrients in the soil matrix are not dominantly in forms available for plant uptake. There were significant residual effects for total potassium in the site with low initial nutrient levels. The soil content of bioavailable phosphorus, nickel, zinc, copper, and cobalt was in general below detectable levels.     

The enumeration and characterization of bacteria and fungi associated with marine wood-boring isopods,and the ability of these microorganisms to digest cellulose and wood

Bacteria and fungi associated with the marine wood-boring isopods Limnoria lignorum and Sphaeroma serratum, and with their wood burrows and seawater were investigated. Plate counts using nutrient agar and Czapex Dox agar media in natural and in artificial seawater were used. The diversity and number of bacteria associated with the two isopods were much higher than those associated with wood or seawater, whereas the opposite was true for fungi. The hydrolytic activity of the predominant genera on carboxymethylcellulose and on different types of wood was investigated. The magnitude of fungal cellulase activity exceeded that of bacteria. Activities of bacterial extracellulases exceeded those of intracellulases, while the opposite was observed for fungi. Cellulolytic activity of the predominant isolates biodegraded labkh, peach, white oak and mahogany in decreasing order of activity. Evidence provided by the cellulolytic activities, detected in woodcontaining cultures, suggests that the predominant micro-organisms isolated may play an important role in the woodboring process. Specimens used in the present study were collected from Port Fouad at Port Said Harbour, Egypt.     

Organic and inorganic phosphorus uptake by bacteria in a plug-flow microcosm

Phosphorus (P) is a vital nutrient for sustaining natural water productivity. Both particulate and dissolved forms of organic and inorganic P are potentially important sources of bioavailable P for primary and secondary producers. A microcosm system to imitate the bacterial community in Plym river sediment and pore water is described and bacterial uptake rates for inorganic and organic phosphorus are presented in this paper. The aim of this study was to investigate the uptake of two organic phosphorus compounds (phytic acid and D-glucose-6-phosphate) by freshwater bacteria. The bioreactors comprise glass columns packed with two types of small glass beads on which bacterial biofilm can develop. The glass beads with different porosity were introduced to simulate River SPM. The selected P compounds spiked into the inflow of the microcosm, and measured the step change of P concentration in the outflow to investigate the behavior of bacterial uptake of nutrients. The results showed that organic phosphorus was converted into inorganic phosphorus but the conversion rate depended on the type of phosphorus species. One experiment suggested that phytic acid (refractory) could displace phosphate from the biofilm surface; the other experiment showed that D-glucose-6-phosphate (labile) could be hydrolysed and utilized easily by the bacteria. The results also suggested that bacteria might break down the C-P bonds to utilize the carbon. Further experiments should investigate the effect of varying the C:N:P ratio in the microcosm system to determine which nutrient limits bacteria uptake.