Trophic interactions within the microbial food web in the South China Sea revealed by size-fractionation method

To define nanoflagellate-bacteria interactions and potential trophic levels within the microbial food web in the oligotrophic South China Sea, we conducted fourteen size-fractionation experiments in which seawater was filtered through 1, 2, 5, 10, 20, 60, and 200 μm membranes or meshes and the growth of four groups of picoplankton, Prochlorococcus, Synechococcus, high DNA heterotrophic bacteria, and low DNA heterotrophic bacteria were monitored in each filtrate after 24 hours of incubation. Removing grazers by filtration would relieve the grazing pressure on lower trophic levels which finally influenced the net growth rates of picoplankton. The growth patterns of Prochlorococcus and Synechococcus were similar, with higher growth rates in the < 1 μm or < 2 μm treatments, a second peak in the < 10 μm treatments and often a third peak in the < 200 μm treatments. The net growth rates of low DNA heterotrophic bacteria were little influenced by size-fractionation. Due to a subgroup of high DNA heterotrophic bacteria with larger size and higher DNA content which appeared to resist the grazing by < 5 μm nanoflagellates, the net growth rates of high DNA heterotrophic bacteria were higher in the < 2 μm or < 5 μm treatments with a second peak in the < 60 μm treatments. A general pattern of five potential trophic levels (< 2 μm, 2-5 μm, 5-10 μm, 10-60 μm, 60-200 μm) was revealed combining all the experiments, confirming the existence of multiple trophic levels within the microbial food web in the oligotrophic South China Sea.     

Description of Trichotokara nothriae n. gen. et sp. (Apicomplexa, Lecudinidae) - An intestinal gregarine of Nothria conchylega (Polychaeta, Onuphidae)

The trophozoites of a novel gregarine apicomplexan, Trichotokara nothriae n. gen. et sp., were isolated and characterized from the intestines of the onuphid tubeworm Nothria conchylega (Polychaeta), collected at 20 m depth from the North-eastern Pacific Coast. The trophozoites were 50-155 μm long with a mid-cell indentation that formed two prominent bulges (anterior bulge, 14-48 μm wide; posterior bulge, 15-55 μm wide). Scanning electron microscopy (SEM) demonstrated that approximately 400 densely packed, longitudinal epicytic folds (5 folds/μm) inscribe the surface of the trophozoites, and a prominently elongated mucron (14-60 μm long and 6-12 μm wide) was covered with hair-like projections (mean length, 1.97 μm; mean width, 0.2 μm at the base). Although a septum occurred at the junction between the cell proper and the mucron in most trophozoites, light microscopy (LM) demonstrated that the cell proper extended into the core of the mucron as a thin prolongation. A spherical nucleus (8-20 μm) was situated in the middle of the trophozoites, and gamonts underwent caudal syzygy. The small subunit (SSU) rDNA sequence and molecular phylogenetic position of T. nothriae was also characterized. The sequence from this species was the most divergent of all SSU rDNA sequences currently known from gregarines and formed a weakly supported clade with Lecudina polymorpha, which also possesses densely packed epicyctic folds (3-5 folds/μm) and a prominently elongated mucron.     

Elk Kelp, Pelagophycus porra, distribution limited due to susceptibility of microscopic stages to high light

Elk Kelp, Pelagophycus porra (Leman) Setchell, is commonly observed in deep (20-50 m) water along the outer edge of Giant Kelp, Macrocystis pyrifera (C. Agardh), forests in southern California, USA and northern Baja California, Mexico, but rarely occurs in shallower water or within the adjacent M. pyrifera beds. To investigate the factors that limit P. porra from establishing populations within these shallower habitats, juvenile P. porra sporophytes were transplanted from a deep (20 m) water P. porra zone to shallower (15 and 8 m) sites within and inside an adjacent M. pyrifera beds. Transplanted P. porra exhibited no differences in survival or growth among depths, although reproductive maturity was observed only at the two shallower sites. When P. porra propagules were experimentally introduced to areas under dense M. pyrifera canopies and areas cleared of the M. pyrifera canopies within the shallower M. pyrifera bed, P. porra still failed to recruit even though this procedure resulted in a four-fold increase in recruitment in the natural P. porra zone. Laboratory-based culturing of P. porra microscopic stages revealed that they grew and survived better under low light conditions characteristic of the natural P. porra zone (2-4 μmol photons m^− 2 s^− 1) than under higher light conditions characteristic of the M. pyrifera beds(18-20 μmol photons m^− 2 s^− 1). Pulse-amplitude modulated (PAM) fluorometry indicated that while naturally-occurring P. porra's adult sporophytes were able to photoacclimate to increasing irradiance as they grew from the benthos towards the surface, P. porra's microscopic stages were unable to photoacclimate to increased irradiances, and subsequently exhibited 100% mortality under these higher light conditions. Altogether, our study suggests that vulnerability of P. porra microscopic stages to higher irradiances appears to be the primary factor inhibiting P. porra from establishing populations in shallower water and stresses the importance of a multiple life-history approach when investigating species distributions.     

Sorgoleone,a sorghum root exudate: Algicidal activity and acute toxicity to the ricefish Oryzias latipes

The discovery of natural and natural-based compounds has resulted in its application as an alternative to synthetic algicides to control harmful algae in aquatic systems. Of the many natural-product-based algicides, sorgoleone, a natural plant product from Sorghum bicolor root exudates has been investigated for its controlling effect on different algal species and its acute fish toxicity. Growth of the blue green algal species Microcystis aeruginosa Kützing was completely inhibited by the crude methanol extract of sorghum root at 20 μg mL⁻¹. The most noticeable inhibition was observed in the bioassay of n-hexane soluble extract, where 98% growth inhibition occurred in M. aeruginosa at the concentration of 1.25 μg mL⁻¹. Sorgoleone very effectively controlled blue green algae inhibiting 97% of M. aeruginosa at 0.5 μg mL⁻¹ and 99% of Anabaena affinis Lemmermann at 4 μg mL⁻¹. In contrast, inhibition of the green algae species Chlorella vulgaris Beijerinck and Scenedensmus spp. at 16 μg mL⁻¹ sorgoleone was 87 and 68%, respectively. There were no mortalities or adverse effects observed in any of the fish exposed to water control, solvent control, and a nominal concentration of 1 μg mL⁻¹ during the test period. The no observed effect concentration (NOEC) value was 1.5 μg mL⁻¹ for the tested fish (O. latipes). Sorgoleone can be considered as an effective and an ecologically and environmentally sustainable approach to controlling harmful algae.     

Effects of UV radiation and nitrate limitation on the production of biogenic sulfur compounds by marine phytoplankton

We tested the effects of UV radiation (UVR) and nitrate limitation on the production of dimethylsulfide (DMS), particulate dimethylsulfoniopropionate (DMSPp), and particulate dimethylsulfoxide (DMSOp) in natural seawater from the Gulf of Mexico and in phytoplankton cultures. DMS/Chl a ratios in PAR-only and PAR + UV-exposed seawater were 0.44–2.0 and 0.46–1.9 nmol DMS μg⁻¹ Chl a, respectively, whereas the ratios in cultures of Amphidinium carterae were 1.0–2.2 nmol μg⁻¹ in PAR-exposed samples and 0.91–2.1 nmol μg⁻¹ in PAR + UV-exposed samples. These results suggested that UVR did not substantially affect DMS/Chl a ratios in seawater and A. carterae culture samples. Similarly, UVR had no significant effect on DMSOp/Chl a in seawater samples (0.83–1.6 nmol DMSO μg⁻¹ Chl a for PAR + UV vs. 0.70–1.5 nmol μg⁻¹ for PAR-exposed seawater samples, respectively) or in A. carterae cultures (0.20–1.3 and 0.19–0.88 nmol DMSO μg⁻¹ Chl a in PAR + UV- and PAR-exposed cultures, respectively). In an experiment with the diatom, Thalassiosira oceanica, the culture was grown in high nitrate (30 μM) or low nitrate (6 μM) media and exposed to PAR-only or PAR + UV. The low nitrate, PAR-only samples showed an increase of intracellular dimethylsulfoniopropionate (DMSP) concentration from 2.1 to 15 mmol L⁻¹ in 60 h, but the increase occurred only after cultures reached the stationary phase. Cultures of T. oceanica grown under UVR had lower growth rates than those under PAR-only (μ′ = 0.17 and 0.32 d⁻¹, respectively) and perhaps did not experience severe nitrate limitation even in the low nitrate treatment. These results suggest that the elevated UVR in low nitrate environments could result in reduction of DMSP in some species, whereas DMSP concentrations would not be affected in eutrophic areas.     

Abundance of amoA genes of ammonia-oxidizing archaea and bacteria in activated sludge of full-scale wastewater treatment plants

In this study, the abundance and sequences of amoA genes of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were determined in seven wastewater treatment plants (WWTPs) whose ammonium concentrations in influent and effluent wastewaters varied considerably (5.6-422.3 mgN l⁻¹ and 0.2-29.2 mgN l⁻¹, respectively). Quantitative real-time PCR showed that the comparative abundance of AOA and AOB amoA genes differed among the WWTPs. In all three industrial WWTPs, where the influent and effluent contained the higher levels of ammonium (36.1-422.3 mgN l⁻¹ and 5.3-29.2 mgN l⁻¹, respectively), more than four orders of magnitude higher numbers of AOB amoA genes than AOA amoA genes arose (with less than the limit of detection of AOA amoA genes). In contrast, significant numbers of AOA amoA genes occurred in all municipal WWTPs (with ammonium levels in the influent and effluent of 5.6-11.0 mgN l⁻¹ and 0.2-3.0 mgN l⁻¹, respectively). Statistical analysis suggested that compared to other plants’ parameters, the ammonium levels in the plants’ effluent showed correlation with the highest p value to the abundance of AOA amoA genes.     

Cultivation of shear stress sensitive microorganisms in disposable bag reactor systems

Technical scale (≥5 l) cultivations of shear stress sensitive microorganisms are often difficult to perform, as common bioreactors are usually designed to maximize the oxygen input into the culture medium. This is achieved by mechanical stirrers, causing high shear stress. Examples for shear stress sensitive microorganisms, for which no specific cultivation systems exist, are many anaerobic bacteria and fungi, such as basidiomycetes. In this work a disposable bag bioreactor developed for cultivation of mammalian cells was investigated to evaluate its potential to cultivate shear stress sensitive anaerobic Eubacterium ramulus and shear stress sensitive basidiomycetes Flammulina velutipes and Pleurotus sapidus. All cultivations were compared with conventional stainless steel stirred tank reactors (STR) cultivations. Good growth of all investigated microorganisms cultivated in the bag reactor was found. E. ramulus showed growth rates of μ = 0.56 h⁻¹ (bag) and μ = 0.53 h⁻¹ (STR). Differences concerning morphology, enzymatic activities and growth in fungal cultivations were observed. In the bag reactor growth in form of small, independent pellets was observed while STR cultivations showed intense aggregation. F. velutipes reached higher biomass concentrations (21.2 g l⁻¹ DCW vs. 16.8 g l⁻¹ DCW) and up to 2-fold higher peptidolytic activities in comparison to cell cultivation in stirred tank reactors.     

Growth rates of baldcypress (Taxodium distichum) seedlings in a treated effluent assimilation marsh

Wetlands have proven effective at improving water quality of treated wastewater effluent, which in turn promotes increased primary productivity and vertical accretion. Baldcypress (Taxodium distichum) seedlings grown under different conditions (bare root and potted) were planted in four subunits of an effluent assimilation marsh and a control marsh in southeast Louisiana, USA, and basal diameter growth was monitored over one growing season. Mean basal diameter growth for seedlings in the assimilation subunits ranged from 16.1 (±1.4) mm to 9.5 (±0.9) mm, whereas growth for seedlings planted in the control marsh was 6.4 (±0.9) mm. Seedlings planted nearest the outfall experienced greater basal diameter growth (18.1 ± 2.6) compared to those planted 700 m away (8.0 ± 0.9), with growth generally decreasing with distance. Potted seedlings experienced greater growth (19.1 ± 1.0 and 20.6 ± 1.0 for five-month-olds and ten-month olds, respectively) than bare root seedlings (4.6 ± 0.6 and 4.0 ± 0.4 for one-year-olds and two-year olds, respectively). Planting assimilation marshes with baldcypress seedlings can be an effective restoration tool for coastal Louisiana, which will provide hurricane protection and improved surface water quality. Wastewater treatment wetlands may offer an effective tool for restoring coastal baldcypress (T. distichum)-water tupelo (Nyssa aquatic) swamps in Louisiana.     

Exposure provides refuge from a rootless invasive macrophyte

Free-floating Utricularia inflata Walt. has the potential to alter native isoetid communities as it expands its range from the Atlantic coastal plain into northeastern New York lakes. This field study assessed (1) in situ growth potential for U. inflata at varying depths (1.0-3.0 m), (2) displacement of U. inflata from sites with different exposures to wind and water movement, and (3) U. inflata's relative abundance over a depth range (0.5 m, 1.0 m, 1.5 m, 2.0 m, and 2.5 m) at each of nine Adirondack Mountain lake sites varying in exposure. Plants grew well in shallow water (RGR: 0.014-0.039 day⁻¹) at depths from 1.0 m to 2.5 m, but lost mass at 3.0 m. Significantly fewer U. inflata plants remained at sites and depths with greater exposure to wave action, as well as those with greater water current. Vegetation sampling confirmed greater relative frequency of U. inflata at sheltered sites and along deeper contours. Despite its potential to grow well in shallow water, water movement can prevent the accumulation of U. inflata there, and thus provide a refuge for native species able to withstand wave exposure.     

The influence of nutritional conditions on metal uptake by the mixotrophic dual symbiosis harboring vent mussel Bathymodiolus azoricus

The vent mussel Bathymodiolus azoricus, host thioautotrophic and methanotrophic bacteria, in their gills and complementary, is able to digest suspended organic matter. But the involvement of nutritional status in metal uptake and storage remains unclear. The influence of B. azoricus physiological condition on its response to the exposure of a mixture of metals in solution is addressed. Mussels from the Menez Gwen field were exposed to 50 μg L^− 1 Cd, plus 25 μg L^− 1 Cu and 100 μg L^− 1 Zn for 24 days. Four conditions were tested: (i) mussels harboring both bacteria but not feed, (ii) harboring only methanotrophic bacteria, (iii) without bacteria but fed during exposure and (iv) without bacteria during starvation. Unexposed mussels under the same conditions were used as controls. Eventual seasonal variations were assessed. Metal levels were quantified in subcellular fractions in gills and digestive gland. Metallothionein levels and condition indices were also quantified. Gill sections were used for fluorescence in situ hybridization (FISH) to assess the temporal distribution of symbiotic associations. Starvation damages metal homeostasis mechanisms and increase the intracellular Zn and MT levels function. There is a clear metallic competition for soluble and insoluble intracellular ligands at each condition. Seasonal variations were observed at metal uptake and storage.     

Light-dependent phosphate uptake of a submersed macrophyte Myriophyllum spicatum L.

The uptake kinetics of phosphate (Pi) by Myriophyllum spicatum was determined from adsorption and absorption under light and dark conditions. Pi uptake was light dependent and showed saturation following the Michaelis-Menten relation (in light: V = 16.91 × [Pi](1.335 + [Pi]), R² = 0.90, p < 0.001; in the dark: V = 5.13 × [Pi](0.351 + [Pi]), R² = 0.77, p < 0.001). Around 77% of the loss of Pi in the water column was absorbed into the tissue of M. spicatum, and only 23% was adsorbed on the surface of the plant shoots. Our study shows that M. spicatum shoots have a much higher affinity (in light: 3.9 μmol g⁻¹ dw h⁻¹ μM⁻¹; in the dark: 3.7 μmol g⁻¹ dw h⁻¹ μM⁻¹) and V_max (maximum uptake rate, shoot light) for Pi uptake than many other aquatic macrophytes (in light: 0.002-0.23 μmol g⁻¹ dw h⁻¹ μM⁻¹; in the dark: 0.002-0.19 μmol g⁻¹ dw h⁻¹ μM⁻¹), which may provide a competitive advantage over other macrophytes across a wide range of Pi concentrations.     

Separation and purification of phycocyanin from Spirulina sp. using a membrane process

The highest purity ratio of phycocyanin extract was obtained when fresh biomass was used as raw material. The crude extract was purified by membrane process using microfiltration and ultrafiltration. Membrane of pore sizes 5 μm, at feed flow rate of 150 mL min⁻¹, permeate flux of 58.5 L h⁻¹ m⁻² was selected for coarse filtration and membrane with pore size 0.8/0.2 μm at the flow rate of 100 mL min⁻¹, permeate flux of 336 L h⁻¹ m⁻² was selected for fine filtration, giving phycocyanin recovery of 88.6% and 82.9%, respectively. For ultrafiltration, membrane with MWCO at 50 kDa, 69 kPa and 75 mL min⁻¹ of flow rate with a mean permeate flux 26.8 L h⁻¹ m⁻² and a retention rate of 99% was found to be optimal. Under these filtration conditions, food grade phycocyanin with the purity around 1.0 containing c-phycocyanin as the major component was obtained.     

An improved protocol for electroporation in members of the genus Gordonia

Gordonia are high GC gram-positive bacteria that have not yet been exploited well for biotechnological purposes because of the limited genetic tools. Described here is an improved protocol for electroporation, which is useful for several Gordonia species. The maximum transformation efficiency obtained was 2.8 × 10⁴/μg (Gordonia rubropertinctus, Gordonia sp), and 1.7 × 10³/μg (Gordonia amarae).     

Molecular mechanism regulating myosin and cardiac functions by ELC

The essential myosin light chain (ELC) is involved in modulation of force generation of myosin motors and cardiac contraction, while its mechanism of action remains elusive. We hypothesized that ELC could modulate myosin stiffness which subsequently determines its force production and cardiac contraction. Therefore, we generated heterologous transgenic mouse (TgM) strains with cardiomyocyte-specific expression of ELC with human ventricular ELC (hVLC-1; TgM^hVLC-1) or E56G-mutated hVLC-1 (hVLC-1^E56G; TgM^E56G). hVLC-1 or hVLC-1^E56G expression in TgM was around 39% and 41%, respectively of total VLC-1. Laser trap and in vitro motility assays showed that stiffness and actin sliding velocity of myosin with hVLC-1 prepared from TgM^hVLC-1 (1.67 pN/nm and 2.3 μm/s, respectively) were significantly higher than myosin with hVLC-1^E56G prepared from TgM^E56G (1.25 pN/nm and 1.7 μm/s, respectively) or myosin with mouse VLC-1 (mVLC-1) prepared from C57/BL6 (1.41 pN/nm and 1.5 μm/s, respectively). Maximal left ventricular pressure development of isolated perfused hearts in vitro prepared from TgM^hVLC-1 (80.0 mmHg) were significantly higher than hearts from TgM^E56G (66.2 mmHg) or C57/BL6 (59.3 ± 3.9 mmHg). These findings show that ELCs decreased myosin stiffness, in vitro motility, and thereby cardiac functions in the order hVLC-1 > hVLC-1^E56G ≈ mVLC-1. They also suggest a molecular pathomechanism of hypertrophic cardiomyopathy caused by hVLC-1 mutations.     

Effects of Bacillus thuringiensis toxin Cry1Ac and Beauveria bassiana on Asiatic corn borer (Lepidoptera: Crambidae)

In this study, interactions between Cry1Ac, a toxic crystal protein produced by Bacillus thuringiensis (Berliner), and Beauveria bassiana on the mortality and survival of Ostrinia furnacalis was evaluated in the laboratory. The results showed that Cry1Ac is toxic to O. furnacalis. Not only were larval growth and development delayed, but pupation, pupal weight and adult emergency also decreased when larvae were fed on artificial diet containing purified Cry1Ac toxin. When third instars O. furnacalis were exposed to combination of B. bassiana (1.8 × 10⁵, 1.8 × 10⁶ or 1.8 × 10⁷ conidia ml⁻¹) and Cry1Ac, (0.2 or 0.8 μg g⁻¹), the effect on mortality was additive, however, the combinations of sublethal concentrations showed antagonism between Cry1Ac (3.2 or 13 μg g⁻¹) and B. bassiana (1.8 × 10⁵ or 1.8 × 10⁶ conidia ml⁻¹). When neonates were reared on sublethal concentrations of Cry1AC until the third instar, and survivors exposed B. bassiana conidial suspension, such treatments showed additive effect on mortality of O. furnacalis except for the combination of Cry1Ac (0.2 μg g⁻¹) and B. bassiana (1.8 × 10⁶ conidia ml⁻¹) that showed antagonism.     

The relationship between water availability and anatomical characters in Carex hirta

The effects of edaphic moisture in anatomical characters were evaluated in two different populations of Carex hirta L. with three watering treatment for 6 months to evaluate stability, and determined taxonomic value. Water availability increased (p < 0.001) leaf thickness from 239 to 289 μm, metaxylem vessel diameter from 17 to 23 μm, air cavity size from 10 to 24% and adaxial epidermal cell height from 18 to 34 μm, and abaxial from 11 to 16 μm, adaxial epidermal cell length from 54 to 105 μm, and abaxial from 35 to 86 μm, and adaxial epidermal cell width from 20 to 33 μm, and abaxial from 15 to 23 μm. Stomatal index and the number of cells in the girder of sclerenchyma did not vary with water availability, hence these traits have taxonomic value. Other characters (the length and amplitude of wall undulations in the epidermal cells, the number of bulliform cells) have a doubtful relation with water availability, because they are variable even in constant homogeneous conditions.     

Cadmium accumulation in Atriplex halimus subsp. schweinfurthii and its influence on growth,proline, root hydraulic conductivity and nutrient uptake

Atriplex halimus subsp. schweinfurthii is a newly found cadmium (Cd)-hyperaccumulator, but there have been no detailed studies on its physiological responses when Cd is hyperaccumulated. A. halimus was grown in hydroponic conditions to investigate the effect of cadmium chloride (CdCl₂) on growth, water status, leaf chlorophyll concentration, proline and Cd accumulation. Treatments were prepared by adding 0, 50, 100, 200 and 400 μM CdCl₂ to the nutrient medium. Plant growth was significantly affected at high-Cd treatments. Increased CdCl₂ decreased chlorophyll concentration, transpiration and root hydraulic conductivity (L₀). Hence water flux had only a little effect on the uptake of Cd in A. halimus seedlings. In contrast, proline content increased with increasing CdCl₂ concentration. Plants accumulated substantial amount of Cd in different plant parts (shoot and root). Most of the Cd taken up was retained in roots (606.51 μg g⁻¹DW after 15 d at 400 μM CdCl₂). The addition of Cd in the culture medium affected calcium (Ca) and potassium (K) nutrition in both shoot and root. A. halimus provides a new plant resource for exploring the mechanism of Cd hyperaccumulation and has potential for use in the phytostabilization of Cd-contaminated salt soils.     

Flightin Is Necessary for Length Determination, Structural Integrity, and Large Bending Stiffness of Insect Flight Muscle Thick Filaments

Despite the fundamental role of thick filaments in muscle contraction, little is known about the mechanical behavior of these filaments and how myosin-associated proteins dictate differences between muscle types. In this study, we used atomic force microscopy to study the morphological and mechanical properties of fully hydrated native thick filaments isolated from indirect flight muscle (IFM) of normal and mutant Drosophila lacking flightin (fln⁰). IFM thick filaments from newly eclosed (0-1 h old) wild-type flies have a mean length of 3.04 ± 0.05 μm. In contrast, IFM thick filaments from newly eclosed fln⁰ flies are more variable in length and, on average, are significantly longer (3.90 ± 1.33 μm) than wild-type filaments from flies of the same age. In the absence of flightin, thick filaments can attain lengths > 300% of wild-type filaments, indicating that flightin is required for setting the proper filament length in vivo. Filaments lacking flightin are structurally compromised, and filament preparations from fully matured 3- to 5-day-old adult fln⁰ IFM yielded fragments of variable length much shorter than 3.20 ± 0.04 μm, the length obtained from wild-type flies of similar age. The persistence length, an index of bending stiffness, was calculated from measurements of filament end-to-end length and contour length. We show that the presence of flightin increases persistence length by more than 40% and that wild-type filaments increase in stiffness with age. These results indicate that flightin fulfills an essential role in defining the structural and mechanical properties of IFM thick filaments.     

Diversity of Bacteria and Archaea from a landfill in Chandigarh,India as revealed by culture-dependent and culture-independent molecular approaches

The bacterial community structure of a municipal landfill in Chandigarh, India was analysed by culture-dependent as well as culture-independent molecular approaches, and archaeal structure by the latter method. Samples were collected in two phases from the surface and a depth of 0.91 m in June, 2004 and from 0.91 m, 1.52 m and 1.68 m in May, 2005. After serial dilutions, samples were plated onto tryptic soy agar (TSA), plate count agar (PCA), tryptic soy broth agar (TSBA) and TSBA100 (TSBA diluted 100 times and solidified with agarose), and incubated aerobically at 30 °C. The number of bacteria (CFU) on different media ranged between 9.4 × 10⁵ g⁻¹ (on PCA) and 1.9 × 10⁷ g⁻¹ (on TSA) (wet weight). The numbers of bacteria enumerated from plates incubated anaerobically (anaerobic agar and reinforced clostridial agar) were 2.1 × 10⁷ and 1.7 × 10⁶ g⁻¹, respectively. Of the 468 isolated and purified bacteria (183 in the first phase and 285 in the second phase), 135 were characterised using phenotypic characteristics as well as 16S rRNA gene sequence analysis. It was found that members of the phylum Firmicutes were overwhelmingly predominant (86.6%) in the landfill, followed by Actinobacteria (9.6%) and Proteobacteria (3.7%). Among the Firmicutes, at least 17 species from the single genus Bacillus were the most abundant inhabitants of the landfill. Detailed polyphasic characterisation of many of these isolates led to the discovery of a novel genus Paenisporosarcina (and the species P. quisquiliarum), a novel species of Microbacterium, M. immunditiarum, and reclassification of Sporosarcina macmurdoensis, Pelagibacillus goriensis, Bacillus silvestris, Bacillus insolitus, Bacillus psychrotolerans and Bacillus psychrodurans. Culture-independent analysis of two 16S rRNA gene libraries also revealed that the phylum Firmicutes was the predominant group in this community. The diversity of Archaea was found to be limited mainly to members of two orders: Methanosarcinales and Methanomicrobiales of the phylum Euryarchaeota. When these results were compared to those reported earlier on similar studies, it was found that irrespective of differences in composition of municipal solid waste (especially compostable organic matter and paper) and climate, the members of bacterial and archaeal communities in landfills of many countries remained broadly similar.     

pH-control modes in a 5-L stirred-tank bioreactor for cell biomass and exopolysaccharide production by Tremella fuciformis spore

The effect of pH-control modes on cell growth and exopolysaccharide production by Tremella fuciformis was evaluated in a 5-L bioreactor. The results show that the maximal dry cell weight (DCW) and exopolysaccharide production were 23.57 and 4.48 g L⁻¹ in pH-stat fermentation, where the maximal specific growth rate (μ_max) and specific production rate of exopolysaccharide (P_P/X) were 1.03 and 0.24 d⁻¹, respectively; under pH-shift cultivation, the maximal DCW and exopolysaccharide production were 30.57 and 3.90 g L⁻¹, where the μ_max and P_P/X were 1.21 and 0.06 d⁻¹. Unlike batch fermentation, maximal DCW and exopolysaccharide production merely reached 15.04 and 2.0 g L⁻¹, where the μ_max and P_P/X were 0.86 and 0.05 d⁻¹, respectively. These results suggest that a pH-stat strategy is a more efficient way of performing the fermentation process to increase exopolysaccharide production. Furthermore, this research has also proved that the three-stage pH-control mode is effective for cell growth.