Separation of Listeria monocytogenes and Salmonella berta from a complex food matrix by aqueous polymer two-phase partitioning

In the present study, the use of aqueous polymer two-phase systems for separation of pathogenic bacteria from a complex food sample was investigated. Three different two-phase systems, a polyethylene glycol 3350/dextran T 500, a methoxy polyethylene glycol 5000/dextran T 500 and a polyethylene glycol 3350/hydroxypropyl starch system, were compared at pH 3 and pH 6 for their capacity to separate the pathogenic bacteria Listeria monocytogenes and Salmonella berta from a Cumberland sausage. In all three phase systems, the food particles partitioned to the lower phase. Best performance was obtained by the polymer combinations, polyethylene glycol 3350/dextran T 500 and polyethylene glycol 3350/hydroxypropyl starch. In these systems, Salmonella berta partitioned to the hydrophobic upper phase both at pH 3 and pH 6 with an average partitioning ratio of 80% and a recovery of 56%. Listeria monocytogenes partitioned to the upper phase at pH 3 only with an average partitioning ratio of 72% and a recovery of 45%. This method may become a valuable tool for separation of bacteria from complex food matrices.     

Solution blowing of submicron-scale cellulose fibers

Solution blowing is an innovative process for spinning micro-/nano-fibers from polymer solutions using high-velocity gas flow as fiber forming driving force. Submicron-scale cellulose fibers were successfully solution blown by two improvement measures. First, cellulose solution was directly blown to fibers of 260-1900nm in diameter by raising the air temperature along the spinning line which was proved to accelerate the evaporation of solvent and fiber forming. Second, coaxial solution blowing technique was established with cellulose solution and polyethylene oxide (PEO) solution used as core and shell liquids, respectively. The core-shell structures of the fibers were examined by SEM and TEM. Cellulose fibers with diameter between 160nm and 960nm were further obtained after removing PEO shell. X-ray diffraction studies showed that the two kinds of submicron-scale cellulose fibers are mostly amorphous.     

Enhancement of L+-lactic acid production using mycelial flocs of Rhizopus oryzae

L(+)-Lactic acid production was enhanced in the culture of Rhizopus oryzae using mycelial flocs formed by addition of 3 g/L mineral support and 5 ppm polyethylene oxide. By addition of the mineral support, an electrostatic repulsion between mycelia increased by 3.5-fold compared to that of mycelia, which allowed a dispersed growth of R. oryzae in the early growth phase. In conventional culture the morphology of R. oryzae is that of a pellet-like cake, however, when support and polyethylene oxide are added to the culture, the morphology of R. oryzae takes on a cotton-like appearance. The formation of these cotton-like mycelial flocs was induced by the addition of 5 ppm polyethylene oxide into a 14 h culture containing the mineral support before the formation of the conventional pellet morphology. The cotton-like flocs were also formed in cultures grown in a fermentor. This morphology allowed effective mass transfer inside the flocs and effective fluidity of culture broth in the reactor. L(+)-Lactic acid concentration produced by mycelial flocs in fermentor, with the support and polyethylene oxide, was 103.6 g/L with the yield of 0.86 using 120 g/L of glucose as the substrate for this cultures without both, the concentration was 65.2 g/L. It demonstrates that cotton-like mycelial flocs are the optimal morphology in the culture of R. oryzae. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 461-470, 1997.     

An Insect Herbivore Microbiome with High Plant Biomass-Degrading Capacity

Herbivores can gain indirect access to recalcitrant carbon present in plant cell walls through symbiotic associations with lignocellulolytic microbes. A paradigmatic example is the leaf-cutter ant (Tribe: Attini), which uses fresh leaves to cultivate a fungus for food in specialized gardens. Using a combination of sugar composition analyses, metagenomics, and whole-genome sequencing, we reveal that the fungus garden microbiome of leaf-cutter ants is composed of a diverse community of bacteria with high plant biomass-degrading capacity. Comparison of this microbiome''s predicted carbohydrate-degrading enzyme profile with other metagenomes shows closest similarity to the bovine rumen, indicating evolutionary convergence of plant biomass degrading potential between two important herbivorous animals. Genomic and physiological characterization of two dominant bacteria in the fungus garden microbiome provides evidence of their capacity to degrade cellulose. Given the recent interest in cellulosic biofuels, understanding how large-scale and rapid plant biomass degradation occurs in a highly evolved insect herbivore is of particular relevance for bioenergy.     

Planktonic microbes: Tiny cells at the base of the ocean's food webs

Phytoplankton in the size range 5-100 μm was originally thought to be the primary source of food for most life in the sea. However, smaller planktonic microbes, down to 0.2 μm in size, have been the focus of intensive investigation by marine scientists during the past two decades. These microbes attain high abundance and biomass in all parts of the world ocean. They include non-photosynthesizing bacteria, at least two types of photosynthesizing prokaryotes, and eukaryotic phototrophs. The new information has resulted in a greatly revised concept of how pelagic ecosystems in both marine and freshwater environments function. The original idea of a basically linear food chain from diatoms to copepods to fish has given way to an extremely complex model of trophic interactions within a microbial food web, which supports metazoan food webs via biomass production of both heterotrophic and autotrophic cells.     

瘤胃微生物对纤维素的降解及其应用

瘤胃微生物主要包括细菌、真菌和原生动物。其中,瘤胃细菌和瘤胃真菌能分泌纤维素酶,对纤维素有较强的降解能力,主要介绍了瘤胃微生物对纤维素的降解作用及其广阔的应用前景。     

Influence of decomposer food web structure and nitrogen availability on plant growth

We studied the sensitivity of soil microbial communities and ecosystem processes to variation in the vertical and horizontal structure of decomposer food web under nitrogen poor and N-enriched conditions. Microcosms with humus and litter layer of boreal forest floor, birch seedlings infected with mycorrhizal fungi, and decomposer food webs with differing trophic group and species composition of soil fauna were constructed. During the second growing period for the birch, we irrigated half of the microcosms with urea solution, and the other half with de-ionised water to create two levels of N concentration in the substrate. During the experiment night time respirations of the microcosms were measured, and the water leached through the microcosms was analysed for concentration of mineral N, and nematode numbers. The microcosms were destructively sampled after 37 weeks for plant biomass and N uptake, structure of soil animal and microbial community (indicated by PLFA profiles), and physical and chemical properties of the humus and litter materials. Predatory mites and nematodes had a negative influence on the biomass of their microbivorous and microbi-detritivorous prey, and microbi-detritivores affected the biomass and community structure of microbes (indicated by PLFA-analysis). Moreover, predatory mites and nematodes increased microbial biomass and changed the microbial community structure. The decomposer food web structure affected also N uptake and growth of plants. Microbi-detritivorous fauna had a positive effect, whereas predators of microbial and detritus feeding fauna exerted a negative influence on plant N uptake and biomass production. The impact of a trophic group on the microbes and plant was also strongly dependent on species composition within the group. Nitrogen addition magnified the influence of food web structure on microbial biomass and plant N uptake. We suggest that addition of urea-N to the soil modified the animal-microbe interaction by increasing microbial growth and altering community structure of microbes. The presence of microbi-detritivores and predators reduced loss of carbon from the microcosms, and the food web structure influenced also water holding capacity of the materials. The changes in plant growth, nutrient cycling, size of N and C pools, and in the physical properties of the soil emphasize the importance and diversity of indirect consequences of decomposer food web structure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Immobilized enzymes – valuable tools for the indication of temperature events

Abstract

The enzymes trypsin and urease were covalently tethered to cellulose to utilize their ability to produce colored products as a consequence of enzymatic activity. Therefore, cellulose had to be chemically modified first in order to generate appropriate chemical functionalities. Different approaches including periodate supported oxidation followed by immobilization via reductive amination, insertion of a reactive polymer interface, and cross-linking inside the cellulose matrix were utilized for the immobilization. The success of immobilization was assessed by the quantification of surface-bound protein as well as by recording of enzymatic activities under different conditions. The enzymatic activity of trypsin and urease was maintained best when a hydrophilic intermediate polymer layer was used for immobilization. The applicability of immobilized enzymes as temperature indicators was demonstrated using cross-linked urease.     

舌苔菌群与中医病证诊断的文献研究与思考

摘要：人体与舌苔微生物相互依存,相互影响。现今对舌苔微生态系统的研究主要集中于舌苔菌群。体质、疾病等诸多因素都可对舌苔产生影响,此时舌苔中菌群会有怎样的变化？菌群变化是否具有疾病诊断意义？这些问题已经受到关注和研究。文献研究显示,目前有关舌苔菌群病证诊断研究主要围绕中医心系疾病、脾系疾病和肺系疾病等进行,诸多研究表明脾系疾病湿热证患者,舌苔存在菌群失调,舌苔中细菌总数较正常人群明显升高,心系、肺系疾病暂无较为一致的结论。文献研究表明舌苔菌群的变化与病证诊断密切相关,其可能成为中医病证诊断的一种新方法。     

Soil Food Web Changes during Spontaneous Succession at Post Mining Sites: A Possible Ecosystem Engineering Effect on Food Web Organization?

Parameters characterizing the structure of the decomposer food web, biomass of the soil microflora (bacteria and fungi) and soil micro-, meso- and macrofauna were studied at 14 non-reclaimed 1– 41-year-old post-mining sites near the town of Sokolov (Czech Republic). These observations on the decomposer food webs were compared with knowledge of vegetation and soil microstructure development from previous studies. The amount of carbon entering the food web increased with succession age in a similar way as the total amount of C in food web biomass and the number of functional groups in the food web. Connectance did not show any significant changes with succession age, however. In early stages of the succession, the bacterial channel dominated the food web. Later on, in shrub-dominated stands, the fungal channel took over. Even later, in the forest stage, the bacterial channel prevailed again. The best predictor of fungal bacterial ratio is thickness of fermentation layer. We argue that these changes correspond with changes in topsoil microstructure driven by a combination of plant organic matter input and engineering effects of earthworms. In early stages, soil is alkaline, and a discontinuous litter layer on the soil surface promotes bacterial biomass growth, so the bacterial food web channel can dominate. Litter accumulation on the soil surface supports the development of the fungal channel. In older stages, earthworms arrive, mix litter into the mineral soil and form an organo-mineral topsoil, which is beneficial for bacteria and enhances the bacterial food web channel.     

We and herbivores eat endophytes

Health depends on the diet and a vegetal diet promotes health by providing fibres, vitamins and diverse metabolites. Remarkably, plants may also provide microbes. Fungi and bacteria that reside inside plant tissues (endophytes) seem better protected to survive digestion; thus, we investigated the reported evidence on the endophytic origin of some members of the gut microbiota in animals such as panda, koala, rabbits and tortoises and several herbivore insects. Data examined here showed that some members of the herbivore gut microbiota are common plant microbes, which derived to become stable microbiota in some cases. Endophytes may contribute to plant fibre or antimetabolite degradation and synthesis of metabolites with the plethora of enzymatic activities that they display; some may have practical applications, for example, Lactobacillus plantarum found in the intestinal tract, plants and in fermented food is used as a probiotic that may defend animals against bacterial and viral infections as other endophytic-enteric bacteria do. Clostridium that is an endophyte and a gut bacterium has remarkable capabilities to degrade cellulose by having cellulosomes that may be considered the most efficient nanomachines. Cellulose degradation is a challenge in animal digestion and for biofuel production. Other endophytic-enteric bacteria may have cellulases, pectinases, xylanases, tannases, proteases, nitrogenases and other enzymatic capabilities that may be attractive for biotechnological developments, indeed many endophytes are used to promote plant growth. Here, a cycle of endophytic-enteric-soil-endophytic microbes is proposed which has relevance for health and comprises the fate of animal faeces as natural microbial inoculants for plants that constitute bacterial sources for animal guts.     

Effects of microbivore species composition and basal resource enrichment on trophic-level biomasses in an experimental microbial-based soil food web

Previous theoretical and empirical evidence suggests that species composition within trophic levels may profoundly affect the response of trophic-level biomasses to enhanced basal resources. To test whether species composition of microbivorous nematodes has such an effect in microbial-based soil food webs, I created three microcosm food webs, consisting of bacteria, fungi, bacterial-feeding nematodes (Acrobeloides tricornus, Caenorhabditis elegans), fungal-feeding nematodes (Aphelenchus avenae, Aphelenchoides sp.) and a predatory nematode (Prionchulus punctatus). The food webs differed in species composition at the second trophic level: food web A included A. tricornus and Aph. avenae, food web B included C. elegans and Aphelenchoides sp., and food web AB included all four species. I increased basal resources by adding glucose to half of the replicates of each food web, and sampled microcosms destructively four times during a 22-week experiment to estimate the biomass of organisms at each trophic level. Microbivore species composition significantly affected bacterivore and fungivore biomass but not bacterial, fungal or predator biomass. Greatest bacterivore and fungivore biomass was found in food web A, intermediate biomass in food web AB, and smallest biomass in food web B. Basal resource addition increased the biomass of microbes and microbivores but did not affect predator biomass. Importantly, microbivore species composition did not significantly modify the effect of additional resources on trophic-level biomasses. The presence of a competitor reduced the biomass of A. tricornus and Aph. avenae, in that the biomass of these species was less in food web AB than in food web A, whereas the biomass of C. elegans and Aphelenchoides sp. was not affected by their potential competitors. The biomass of Aph. avenae increased with additional resources in the absence of the competitor only, while the biomass of A. tricornus and Aphelenchoides sp. increased also in the presence of their competitors. The results imply that microbivore species composition may determine the second-level biomass in simple microbe-nematode food webs, but may not significantly affect biomass at other levels or modify the response of trophic-level biomasses to enhanced basal resources. The study also shows that even if the role of predation in a food web is diminished, the positive response of organisms to increased resource availability may still be hindered by competition. Received: 22 June 1998 / Accepted: 28 August 1998     

Mineral and phytochemical influences on foliage selection by the proboscis monkey (Nasalis larvatus)

Primate diets may be influenced by the phytochemical composition of potential food resources. This study examined the protein, fiber, and mineral content of leaves from plant species used as food resources by the proboscis monkey (Nasalis larvatus) in Tanjung Puting National Park, Kalimantan Tengah, Indonesia. In addition, leaf samples were collected from nonfood resources based upon relative density in previously established vegetation plots. Higher concentrations of crude protein, phosphorus, potassium, and zinc were found in young leaves. Mature leaves had higher levels of magnesium, manganese and calcium compared to young leaves. Leaves from species used as food resources were significantly higher in protein (9.9% vs. 8.5%) and lower in fiber (30.5% vs. 40.0% acid detergent fiber) than the leaves from species not used as food sources. Food resources also contained higher concentrations of phosphorus and potassium; nonfood resources contained higher concentrations of calcium and manganese. Proboscis monkeys appear to follow the typical colobine trend: a diet relatively high in protein and low in digestion inhibitors (fiber). Little previous work has examined mineral content as a selection factor in primate food choices. Leaves from species used as food resources contained less calcium (0.35%), iron (34 mg/kg) and phosphorus (0.15%) than dietary standards established for captive nonhuman primates, but values were similar to those established for ruminant herbivores. Other mineral concentrations (potassium, magnesium, manganese, sodium, and zinc) met or exceeded recommended levels for both primates and ruminants. Comparison of diverse nutrients in native diets may provide insight into suitability of domestic animals models for providing adequate diets in captive feeding situations, as well as help define resource limitations in natural environments. Am. J. Primatol. 41:117–128, 1997. © 1997 Wiley-Liss, Inc.     

Exogenous carbon turnover within the soil food web strengthens soil carbon sequestration through microbial necromass accumulation

Exogenous carbon turnover within soil food web is important in determining the trade-offs between soil organic carbon (SOC) storage and carbon emission. However, it remains largely unknown how soil food web influences carbon sequestration through mediating the dual roles of microbes as decomposers and contributors, hindering our ability to develop policies for soil carbon management. Here, we conducted a ¹³C-labeled straw experiment to demonstrate how soil food web regulated the residing microbes to influence the soil carbon transformation and stabilization process after 11 years of no-tillage. Our work demonstrated that soil fauna, as a “temporary storage container,” indirectly influenced the SOC transformation processes and mediated the SOC sequestration through feeding on soil microbes. Soil biota communities acted as both drivers of and contributors to SOC cycling, with 32.0% of exogenous carbon being stabilizing in the form of microbial necromass as “new” carbon. Additionally, the proportion of mineral-associated organic carbon and particulate organic carbon showed that the “renewal effect” driven by the soil food web promoted the SOC to be more stable. Our study clearly illustrated that soil food web regulated the turnover of exogenous carbon inputs by and mediated soil carbon sequestration through microbial necromass accumulation.     

Response of Heterotrophic Planktonic Bacteria to the Zebra Mussel Invasion of the Tidal Freshwater Hudson River

Abstract Invasions of aquatic ecosystems by exotic bivalves are known to cause dramatic changes in phytoplankton and some other groups, but their effect on the microbial component is unknown. The invasion of the tidal freshwater Hudson River by the exotic zebra mussel (Dreissena polymorpha) has caused large changes in several components of the Hudson's food web. Planktonic bacteria in the tidal freshwater Hudson are a major part of the food web, and mediate important processes in the carbon budget. We used a long-term data set, spanning four years prior to the zebra mussel (ZM) invasion and four years post-invasion, to describe ZM effects on planktonic bacteria. Small and meso-scale experiments were conducted to specifically examine direct consumption of bacteria by ZM, as well as effects on protozoans. Bacterial abundances in the Hudson have increased roughly 2× since the ZM arrived, making it clear that direct consumption by Dreissena is a minor process. Experiments show that ZM do not remove bacteria from Hudson River water, but are very effective at clearing flagellated protozoans, the major predator of bacteria. The observed changes in bacterial abundance have not been accompanied by equally large changes in bacterial productivity, suggesting growth is primarily limited by carbon supply. Bacterial production has not declined despite a dramatic decline of phytoplankton, confirming previous suggestions that bacteria and phytoplankton are not strongly linked in the Hudson. As a result of the increase in bacterial abundance and removal of phytoplankton, the absolute and relative contributions of bacterial carbon to living particulate organic carbon (POC) standing stocks have increased dramatically. The maintenance of the bacterial component of the Hudson River's food web may be one mechanism whereby consumers are ``insulated' from effects of zebra mussel consumption of phytoplankton carbon. Received: 24 October 1997; Accepted: 9 February 1998     

Painting and printing living bacteria: engineering nanoporous biocatalytic coatings to preserve microbial viability and intensify reactivity

Latex biocatalytic coatings containing approximately 50% by volume of microorganisms stabilize, concentrate and preserve cell viability on surfaces at ambient temperature. Coatings can be formed on a variety of surfaces, delaminated to generate stand-alone membranes or formulated as reactive inks for piezoelectric deposition of viable microbes. As the latex emulsion dries, cell preservation by partial desiccation occurs simultaneously with the formation of pores and adhesion to the substrate. The result is living cells permanently entrapped, surrounded by nanopores generated by partially coalesced polymer particles. Nanoporosity is essential for preserving microbial viability and coating reactivity. Cryo-SEM methods have been developed to visualize hydrated coating microstructure, confocal microscopy and dispersible coating methods have been developed to quantify the activity of the entrapped cells, and FTIR methods are being developed to determine the structure of vitrified biomolecules within and surrounding the cells in dry coatings. Coating microstructure, stability and reactivity are investigated using small patch or strip coatings where bacteria are concentrated 102- to 103-fold in 5-75 microm thick layers with pores formed by carbohydrate porogens. The carbohydrate porogens also function as osmoprotectants and are postulated to preserve microbial viability by formation of glasses inside the microbes during coat drying; however, the molecular mechanism of cell preservation by latex coatings is not known. Emerging applications include coatings for multistep oxidations, photoreactive coatings, stabilization of hyperthermophiles, environmental biosensors, microbial fuel cells, as reaction zones in microfluidic devices, or as very high intensity (>100 g.L-1 coating volume.h-1) industrial or environmental biocatalysts. We anticipate expanded use of nanoporous adhesive coatings for prokaryotic and eukaryotic cell preservation at ambient temperature and the design of highly reactive "living" paints and inks.     

Bacillus species in the intestine of termites and other soil invertebrates

Soil invertebrates harbour a complex microbial community in their intestinal system. The total number of microbes in the hindgut of soil invertebrates can reach a titre of 10(11) ml(-1). The gut microbes play an indispensable role in the digestion of food and are of ecological importance in the global carbon cycle. The gut microbiota can include a variety of micro-organisms from the three domains Bacteria, Archaea and Eucarya. The bacterial groups from the intestinal systems are mainly affiliated to the proteobacteria, the gram-positive groups Firmicutes and Actinobacteria, the Bacteroides/Flavobacterium branch and the spirochetes. The Archaea are represented by methanogens. The eukaryotic groups consist of protozoa, yeasts and fungi. Intestinal bacteria are involved in the degradation of cellulose, hemicellulose and aromatic compounds as well as nitrogen fixation. They also contribute to the redox status of the gut. Bacilli form a significant portion of the intestinal microbial community of soil invertebrates, especially among cellulose degraders. The diversity and function of bacilli in soil invertebrates will be discussed in this paper.     

Microflora participating in the decomposition of carboxymethyl cellulose continuously added to the soil

The microbial community in the soil was analyzed during four weeks of a continuous enrichment of structural chernozem soil samples with a 0.1% solution of carboxymethyl cellulose (CMC) under aerobic and semianaerobic conditions. During the first 14 d, the total amount of the aerobic and anaerobic, cellulose-degrading microorganisms increased significantly. Various metabolic pathways were u‘ed te decompose the substrate: diverse metabolic systems were activated and different groups of microorganisms preferred in dependence on the presence of oxygen or the source of mineral nitrogen. In the later phases of cultivation, a decrease in the concentration of zymogenous microflora and in the level of substrate mineralization was observed ovon though CM-cellulase activity remained high. During the fourth week of cultivation, a conspicuous increase in the numbers of oligothropic bacteria occurring in the colcnies of the microorganisms degrading cellulose was found. The representatives of prosthecobacteria (Caulobacter, Hyphomicrobium, Prosthecomicrobium spp.) andSeliberia sp. were thus identified. This “microflora of dispersion” attends the zymogenous microbes degrading CMC and indicates later phases of the process of decomposition.