Assessment of bioaerosols at a concentrated dairy operation

Increased bioaerosol loadings in downwind plumes from concentrated animal feeding operations (CAFOs) may increase the risk for allergy and infection in humans. In this study, we monitored airborne concentrations of culturable bacteria and fungi at upwind (background) and downwind sites at a 10,000 milking cow dairy over the course of a year. The average bacterial concentrations at the upwind site were 8.4 × 10³ colony forming units (CFU) m⁻³ and increased to 9.9 × 10⁵ CFU m⁻³ at the downwind edge of the cattle lots, decreasing to 6.3 × 10⁴ CFU m⁻³ 200 m farther downwind. At the same sites, the average fungal concentrations were 515, 945, and 1,010 CFU m⁻³, respectively. Significant correlations between the ambient weather conditions and airborne fungal and bacterial concentrations were identified. Sequence analysis of PCR-amplified DNA from bacterial clones and fungal isolates revealed genus and species level differences between upwind and downwind sites. Although we could not cultivate gram-negative bacteria, bacterial clones at downwind sites identified as being gram-negative matched with the following genera: Acinetobacter, Bradyrhizobium, Escherichia, Idiomarina, Methylobacterium, Ralstonia, and Novosphingobium. Fungal isolates from downwind matched with the following genera: Acremonium, Alternaria, Ascomycte, Aspergillus, Basidiomycete, Cladosporium, Davidiella, Doratomyces, Emericella, Lewia, Onygenales, Penicillium, Rhizopus, and Ulocladium. None of the bacterial and fungal sequence matches were affiliated with genera and species known to be pathogenic to humans. Overall, the data suggest that exposure to bioaerosols in the downwind environment decreases with increasing distance from the open-lot dairy.     

Year-long assessment of airborne endotoxin at a concentrated dairy operation

In this study, we monitored total airborne endotoxins at upwind and downwind sites at a large open-lot dairy each month for a year. At the upwind site, the average airborne concentration was 28.5 endotoxin units (EU) m⁻³, while at the downwind edge of the lot and 200 m from the lot edge, the average concentrations were 169 and 72 EU m⁻³, respectively. At the downwind edge of the lot, there was a significant correlation between the airborne endotoxin concentration and wind speed or air temperature. A comparison between total and inhalable airborne endotoxin concentrations, near the end of the study, revealed no significant differences between the two endotoxin collection methods. Our data suggest that endotoxin exposure can be reduced as one increases their distance from the open-lot dairy.     

Measurements of total and culturable bacteria in the alfresco atmosphere using a wet-cyclone sampler

Alfresco (def. clean, outdoor) airborne bacteria were collected with a commercially available wet-cyclone bioaerosol sampler to demonstrate its use, sample processing and resultant observations of total and culturable bacteria in mid-summer in the mid-Willamette River Valley, OR. Some critiques of the system are given. The maximum and minimum total and culturable airborne bacterial concentrations in the samples were 5.9 × 10⁵ and 8.8 × 10² cells m⁻³, and 1.3 × 10⁴ and 3.1 CFU m⁻³, respectively. What is thought to be a diurnal cycle was also observed for both fractions with highest concentrations during the day and lowest at dawn and dusk. The culturable bacteria as a percentage of the total, was maximal at mid-day (≈ 3%) and minimal at early morning and late evening (≈ 0.5–2%). Contrarily, the total bacteria in the downwind dust plume of a grass seed combine was 2.9 × 10⁶ cells m⁻³ and of these approximately 73% were culturable, a much greater culturable percentage than found in the alfresco outdoor atmosphere.     

Carob pulp as raw material for production of the biocontrol agent <Emphasis Type="Italic">P. agglomerans</Emphasis> PBC-1

Large-scale production has been the major obstacle to the success of many biopesticides. The spreading of microbial biocontrol agents against postharvest disease, as a safe and environmentally friendly alternative to synthetic fungicides, is quite dependent on their industrial mass production from low-cost raw materials. Considerable interest has been shown in using agricultural waste products and by-products from food industry as nitrogen and carbon sources. In this work, carob pulp aqueous extracts were used as carbon source in the production of the biocontrol agent Pantoea agglomerans PBC-1. Optimal sugar extraction was achieved at a solid/liquid ratio of 1:10 (w/v), at 25°C, for 1 h. Batch experiments were performed in shake flasks, at different concentrations and in stirred reactors at two initial inoculums concentrations, 10⁶ and 10⁷ cfu ml⁻¹. The initial sugar concentration of 5 g l⁻¹ allowed rapid growth (0.16 h⁻¹) and high biomass productivity (0.28 g l⁻¹ h⁻¹) and was chosen as the value for use in stirred reactor experiments. After 22 and 32 h of fermentation the viable population reached was 3.2 × 10⁹ and 6.2 × 10⁹ cfu ml⁻¹ in the fermenter inoculated at 10⁶ cfu ml⁻¹ and 2.7 × 10⁹ and 6.7 × 10⁹ cfu ml⁻¹ in the bioreactor inoculated at 10⁷ cfu ml⁻¹. A 78% reduction of the pathogen incidence was achieved with PBC-1 at 1 × 10⁸ cfu ml⁻¹, grown in medium with carob extracts, on artificially wounded apples stored after 7 days at 25°C against P. expansum.     

Quantitative assessment of total and Gram-positive aerobic bacteria in fresh and ambient-temperature-stored sub-tropical marine fish

The current study was undertaken to enumerate Gram-positive bacteria in fresh sub-tropical marine fish and determine the effect of ambient storage (25°C) on the Gram-positive bacterial count. Total and Gram-positive bacteria were enumerated in the muscles, gills and gut of fresh and stored Pseudocaranx dentex, Pagrus auratus and Mugil cephalus on tryptone soya agar (TSA) and TSA with 0.25% phenylethyl alcohol (PEA), respectively. Initial studies indicated that PEA significantly reduced total aerobic bacterial count (TABC) whereas control Gram-positive bacteria were not affected by 0.25% PEA. TABC significantly increased in all fish body parts, whereas Gram-positive aerobic bacterial count (GABC) significantly increased only in the muscles and gills during ambient storage for 15 h. The TABC of the fish species increased from 4.00, 6.13 and 4.58 log cfu g⁻¹, respectively in the muscles, gills, and gut to 6.31, 7.31 and 7.23 log cfu g⁻¹ by the end of storage. GABC increased from 2.00, 3.52 and 2.20 log cfu g⁻¹ to 4.70, 5.85 and 3.36 log cfu g⁻¹. Within each species, TABC were significantly higher in the gills compared to that of muscles and gut; however, no significant differences were found in GABC between muscles and gills. This study demonstrated the potential importance of Gram-positive bacteria in sub-tropical marine fish and their spoilage.     

Airborne concentrations of bacteria and fungi in Thailand border market

Thailand border market is where the local Thais, Cambodians, Laotians, and Burmeses exchange their goods and culture at the border checkpoints. It is considered to be the source of aerial disease transmission especially for foreigners because it is always very crowded with people from all walks of life. Unhealthy air quality makes this area high risk of spread of airborne diseases. This study assessed airborne concentrations of bacteria and fungi in a border market to improve exposure estimates and develop efficient control strategies to reduce health risk. The density and distribution of airborne bacteria and fungi were investigated in the Chong Chom border market in Surin Province, Thailand. Eighteen air sampling sites were taken from outdoors and various work environments including indoor footpaths, wooden handicraft shops, electronic shops, the secondhand clothing shops, and fruit market areas. Exposed Petri plate method and liquid impinger sampler were used for sampling at the breathing zone, 1.5 m above the floor level, during weekend and holiday. Meteorological factors such as relative humidity, temperature, and light intensity were collected by portable data logger. The relative humidity was 67–73%, and temperature 29–33°C, and light varied between 18 and 270 Lux m⁻². Gram-positive and Gram-negative bacteria were found at a mean value of 10⁴ CFU m⁻³, and airborne fungi of 10³ CFU m⁻³ were recorded. The highest concentration of culturable airborne microorganisms was found along the indoor footpath (9.62 × 10⁴ CFU m⁻³ and 750.00 CFU/plate/h for impingement and sedimentation methods, respectively), the fruit market area (7.86 × 10⁴ CFU m⁻³ and 592.42 CFU/plate/h for impingement and sedimentation methods, respectively), and the secondhand clothing shop (4.59 × 10³ CFU m⁻³ and 335.42 CFU/plate/h for impingement and sedimentation methods, respectively) for Gram-positive bacteria, Gram-negative bacteria, and fungi, respectively. The lowest concentration of Gram-positive bacteria, Gram-negative bacteria, and fungi was found only at the outdoor area at 1.53 × 10⁴ CFU m⁻³, 0.93 × 10⁴ CFU m⁻³ and 0.80 × 10³ CFU m⁻³ by means of impingement method and 136.67 CFU/plate/h, 69.25 CFU/plate/h, and 62.00 CFU/plate/h by means of sedimentation methods for Gram-positive bacteria, Gram-negative bacteria, and fungi, respectively. The most frequently present airborne bacteria were identified as Bacillus, Corynebacteria, Diplococcus, Micrococcus, Acinetobacter, Alcaligenes, Enterobacter, and spore former rods. Acremonium, Aspergillus, Cladosporium, Penicillium, and Sporotrichum were the most frequently found aerosol fungi genera. The distribution of airborne microorganisms correlated with relative humidity and light factors based on principal component analysis. In conclusion, the border market is a potential source of aerial disease transmission and a various hazards of bioaerosols for workers, consumers, sellers, and tourists. The bioaerosol concentration exceeded the standard of occupational exposure limit. Many major indicators of allergenic and toxigenic airborne bacteria and fungi, Acinetobacter, Enterobacter, Pseudomonas, Cladosporium, Alternaria, Aspergillus, and Penicillium, were found in the various market environments.     

Air biocontamination in a variety of agricultural industry environments in Egypt: a pilot study

Inhalation of airborne microorganisms and organic dust is an occupational concern among workers in agricultural industries. Airborne microorganisms and particulate matter samples were collected from poultry house, flourmill, textile, and food industry sites by use of liquid impinger and gravimetric samplers. Particulate matter concentrations were recorded at median concentrations of 1.56, 1.92, 4.39, and 0.7 mg/m³ in the occupied poultry house, textile, flourmill, and food indoor working environments, respectively. The highest median particulate matter concentration (27.9 mg/m³) was detected at the flourmill’s stack site. The highest median indoor concentration of culturable airborne bacteria (6.23 × 10⁵ CFU/m³) was found at the occupied poultry-house site and the lowest concentration (4.6 × 10³ CFU/m³) was found at the food industry site. The highest median indoor concentration of culturable airborne fungi (3.15 × 10⁴ CFU/m³) was found at the flourmill site whereas the lowest (1.24 × 10³ CFU/m³) was found at the textile industry site. Bacillus and Staphylococcus were the predominant Gram-positive bacteria whereas Acinetobacter and Klebsiella were the predominant Gram-negative bacteria. Escherichia coli and Salmonella were only detected in the indoor air at the poultry house site. Aspergillus flavus, Aspergillus niger, Penicillium, and yeast were the predominant fungal types at flourmill, textile, food industry, and poultry house, respectively. Workers were continuously exposed to airborne microorganisms at a median value of 10⁴ CFU/m³ in all the industries studied.     

Pseudoxanthomonas bacteria that drive deposit formation of wood extractives can be flocculated by cationic polyelectrolytes

Runnability problems caused by suspended bacteria in water using industries, have, in contrast to biofilms, received little attention. We describe here that Pseudoxanthomonas taiwanensis, a wide-spread and abundant bacterium in paper machine water circuits, aggregated dispersions of wood extractives ("pitch") and resin acid, under conditions prevailing in machine water circuits (10⁹ cfu ml⁻¹, pH 8, 45°C). The aggregates were large enough (up to 50 μm) so that they could be expected to clog wires and felts and to reduce dewatering of the fiber web. The Pseudoxanthomonas bacteria were negatively charged over a pH range of 3.2–10. Cationic polyelectrolytes of the types used as retention aids or fixatives to flocculate "anionic trash" in paper machines were effective in flocculating the Pseudoxanthomonas bacteria. The polyelectrolyte most effective for this purpose was of high molecular weight (7–8 × 10⁶ g mol⁻¹) and low charge density (1 meq g⁻¹), whereas polyelectrolytes that effectively zeroed the electrophoretic mobility (i.e., neutralized the negative charge) of the bacterium were less effective in flocculating the bacteria. Based on the results, we concluded that the polyelectrolytes functioning by bridging mechanism, rather than by neutralization of the negative charge, may be useful as tools for reducing harmful deposits resulting from interaction of bacteria with wood extractives in warm water industry.     

Airborne bacterial emission fluxes from manure-fertilized agricultural soil

This is the first study to quantify the dependence on wind velocity of airborne bacterial emission fluxes from soil. It demonstrates that manure bacteria get aerosolized from fertilized soil more easily than soil bacteria, and it applies bacterial genomic sequencing for the first time to trace environmental faecal contamination back to its source in the chicken barn. We report quantitative, airborne emission fluxes of bacteria during and following the fertilization of agricultural soil with manure from broiler chickens. During the fertilization process, the concentration of airborne bacteria culturable on blood agar medium increased more than 600 000-fold, and 1 m³ of air carried 2.9 × 10⁵ viable enterococci, i.e. indicators of faecal contamination which had been undetectable in background air samples. Trajectory modelling suggested that atmospheric residence times and dispersion pathways were dependent on the time of day at which fertilization was performed. Measurements in a wind tunnel indicated that airborne bacterial emission fluxes from freshly fertilized soil under local climatic conditions on average were 100-fold higher than a previous estimate of average emissions from land. Faecal bacteria collected from soil and dust up to seven weeks after fertilization could be traced to their origins in the poultry barn by genomic sequencing. Comparative analyses of 16S rRNA gene sequences from manure, soil and dust showed that manure bacteria got aerosolized preferably, likely due to their attachment to low-density manure particles. Our data show that fertilization with manure may cause substantial increases of bacterial emissions from agricultural land. After mechanical incorporation of manure into soil, however, the associated risk of airborne infection is low.     

Aerobiological dynamics of potentially pathogenic fungi in a rice agroecosystem in La Habana, Cuba

The aerobiology can play a key role in protecting the rice crop since many fungi can cause serious damage to agricultural areas. In this way, the ideal time to implement different security measures can be identified. To determine the presence of potentially pathogenic fungi in the air of the rice agroecosystem, a weekly monitoring of viable fungi was carried out using a volumetric sampler. Collected fungi were quantified, isolated, and identified based on their morphological characteristics. The results obtained demonstrated that the annual average concentration of filamentous fungi in the atmosphere of rice agroecosystem studied was 1,225 cfu m⁻³ levels ranging between 115 cfu m⁻³ (April) and 2,865 cfu m⁻³ (August). Pyricularia grisea was detected in the air for 5 months, since the second week of June until the first week of October, and highest average concentration (25 cfu m⁻³) was observed in August. Of the meteorological factors evaluated, temperature and relative air humidity influence the concentration of propagules of P. grisea in the air. Besides, other fungi were detected such as Curvularia, Bipolaris, Alternaria, and Cercospora, all with relevance to rice cultivation. This is the first characterization of aeromycological biodiversity in the studied region.     

The viability to a wall shear stress and propagation of <Emphasis Type="Italic">Bifidobacterium longum</Emphasis> in the intensive membrane bioreactor

Bifidobacterium longum grew at 65 L pilot scale of the membrane bioreactor (MBR), externally fitted with ceramic membrane (0.7 m²). Cell mass at the MBR reached 22.18 g L⁻¹ as dry cell weight in 12 h, which is 8.44 times higher than cell mass attained at the vial culture. The growth rate in the vial culture was μ = 0.385 h⁻ and at the batch culture was μ = 1.13 h⁻ in the exponential period and μ = 0.31 h⁻¹ in the stationary period. In the fed-batch mode was μ = 1.102 h⁻¹ for 6 h with inoculation and declined to μ = 0.456 h⁻¹ with feeding of feed medium. The growth rate at the MBR was μ = 0.134 h⁻¹. The number of viable cells was 6.01 × 10¹² cfu L⁻¹ at the batch culture, but increased to 1.15 × 10¹⁴ cfu L⁻¹ at the MBR culture. The specific growth rate of viable cell number (colony-forming units per liter, per hour) improved by 6.01 times from the batch to the MBR culture. The wall shear stress mainly generated by the pump, and the membrane incorporated into the MBR was controlled during the cultivation at the MBR. The viability of B. longum declined to under 10% in the first 2 weeks of the 4-week stability test (40°C) as B. longum was exposed to over wall shear stress 713 Pa, but the viability improved to 30–40% in wall shear stress of 260 Pa or STR culture. The loss in the cell viability can be saved by managing with wall shear stress during the cultivation at the MBR.     

The distribution of picoplankton and nanoplankton in Kongsfjorden,Svalbard during late summer 2006

Abundance and biomass of pico- (<2 μm) and nanoplankton (2–20 μm) were investigated in relation to hydrography in Kongsfjorden, Svalbard (79°N, 12°E) during late summer 2006. Autotrophic and heterotrophic picoplankton abundance ranged from 0.1 × 10⁶ to 35.2 × 10⁶ cells L⁻¹ and from 0.4 × 10⁶ to 20.3 × 10⁶ cells L⁻¹, respectively. The highest number of bacteria in the entire water column was recorded at station 2 at 10 m (22.3 × 10⁸ cells L⁻¹); the lowest concentration was observed at station 1 (6.0 × 10⁸ cells L⁻¹). The abundance of autotrophic and heterotrophic nanoplankton varied from 0.4 × 10⁵ cells L⁻¹ to 46 × 10⁵ cells L⁻¹ and from 0.3 × 10⁶ to 9.1 × 10⁶ cells L⁻¹, respectively. Our results demonstrated that heterotrophic nanoflagellates and bacteria in Kongsfjorden microbial community were relatively important. The structure of plankton communities integrated with environmental variables could act as indicators of the variability of the inflow of Atlantic Water into Kongsfjorden.     

Olive mill wastewater disposal in evaporation ponds in Sfax (Tunisia): moisture content effect on microbiological and physical chemical parameters

The study of the isotherms desorption of olive mill wastewater (OMW) was investigated to describe its water activity under different saturated environments. The microbial biodegradation of OMW during its storage in 5 evaporation ponds located in Agareb (Sfax-Tunisia) was carried out during the oil-harvesting year held 105 days in 2004. Gravimetric static method using saturated salt solutions was used and OMW as placed at 30°C and under different water activities ranging from 0.11 to 0.90. Eight models were taken from the literature to describe experimental desorption isotherms. During storage, the evolution of physico-chemical parameters including pH, temperature, evaporation, humidity, total phosphorus, chemical oxygen demand (COD), biological oxygen demand (BOD) and phenols and three microbiological flora (aerobic mesophilic bacteria, yeasts and moulds) were considered. At 30°C, when relative humidity increased in the experimented ponds of 69, 84 and 90%, the evaporation speed decreased from 1.24 × 10⁻⁵ to 5 × 10⁻⁶ cm³ s⁻¹, from 6 × 10⁻⁵ to 7 × 10⁻⁶ cm³ s⁻¹ and from 5 × 10⁻⁶ to 1.1 × 10⁻⁷ cm³ s⁻¹ respectively. The desorption isotherm exhibited a sigmoidal curve corresponding to type II, typical of many organic material. The GAB and Peleg models gave the best fit for describing the relationship between the equilibrium moisture content and water activity in OMW (R ² = 0.998). During the storage period, the analysis showed an increase of all the physico-chemical parameters studied, except phenols and total phosphorus concentrations. The microbiological study showed the predominance of yeasts and moulds and the decrease of bacteria population after 75 days reflecting both effect of recalcitrant compounds and the water activity on microbial growth.     

The aerobiology of the environment around mechanically ventilated broiler sheds

Aim: To investigate the aerobiology of the environment around mechanically ventilated broiler sheds with the aim of understanding dispersion in the surrounding environment. Methods and Results: Aerosol samples were collected weekly on four different commercial broiler farms through the cycle of 55 days from 2005 to 2007. Samples were collected inside the shed and at varying distances from the sheds. Litter and dust from within the shed were also examined. Members of the genera Staphylococcus (and to a lesser extent Corynebacterium) dominated (10⁶ CFU m^?3) in the outside air at 20 m from the fan and were shown to decrease with distance. At distances of around 400 m, the levels of staphylococci/coryneforms returned to levels typical of those present before the placement of chickens. Escherichia coli levels were low (maximum 100 CFU m^?3) at 20 m. Fungi were present at uniform levels across the broiler cycle. Conclusions: Staphylococci are the dominant organisms present in the air around mechanically ventilated broiler sheds and have the potential to act as an airborne ‘marker organism’. Significant Impact of the Study: The outcomes of this study suggest that the impact of aerosols emitted from broiler sheds could be monitored and managed by examining the levels of staphylococci/coryneforms.     

Non-parametric estimation of thresholds for radiation effects in vertebrate species under chronic low-LET exposures

Databases on effects of chronic low-LET radiation exposure were analyzed by non-parametric statistical methods, to estimate the threshold dose rates above which radiation effects can be expected in vertebrate organisms. Data were grouped under three umbrella endpoints: effects on morbidity, reproduction, and life shortening. The data sets were compiled on a simple ‘yes’ or ‘no’ basis. Each data set included dose rates at which effects were reported without further details about the size or peculiarity of the effects. In total, the data sets include 84 values for endpoint “morbidity”, 77 values for reproduction, and 41 values for life shortening. The dose rates in each set were ranked from low to higher values. The threshold TDR5 for radiation effects of a given umbrella type was estimated as a dose rate below which only a small percentage (5%) of data reported statistically significant radiation effects. The statistical treatment of the data sets was performed using non-parametric order statistics, and the bootstrap method. The resulting thresholds estimated by the order statistics are for morbidity effects 8.1 × 10⁻⁴ Gy day⁻¹ (2.0 × 10⁻⁴–1.0 × 10⁻³), reproduction effects 6.0 × 10⁻⁴ Gy day⁻¹ (4.0 × 10⁻⁴–1.5 × 10⁻³), and life shortening 3.0 × 10⁻³ Gy day⁻¹ (1.0 × 10⁻³–6.0 × 10⁻³), respectively. The bootstrap method gave slightly lower values: 2.1 × 10⁻⁴ Gy day⁻¹ (1.4 × 10⁻⁴–3.2 × 10⁻⁴) (morbidity), 4.1 × 10⁻⁴ Gy day⁻¹ (3.0 × 10⁻⁴–5.7 × 10⁻⁴) (reproduction), and 1.1 × 10⁻³ Gy day⁻¹ (7.9 × 10⁻⁴–1.3 × 10⁻³) (life shortening), respectively. The generic threshold dose rate (based on all umbrella types of effects) was estimated at 1.0 × 10⁻³ Gy day⁻¹.     

Indoor and outdoor airborne fungal propagule concentrations in Mexico City

Thirty homes of asthmatic adults located in Mexico City were examined to determine the predominant culturable fungi and the changes in their airborne concentrations. Fungi were cultured and identified microscopically from air samples collected in naturally ventilated homes, during both wet (July–August) and cool dry (November–December) seasons, and from settled dust from the same homes. Airborne dust from indoor yielded 99–4950 cfu m⁻³, and settled dust 10²–10⁶ cfu g⁻¹ on DG18 agar. The indoor geometric mean concentration of airborne fungi during the cool dry season was 460 cfu m⁻³ while in the wet season it was 141 cfu m⁻³. Similarly, numbers of airborne fungal propagules out of doors decreased 60% between the dry and wet season. In general, the total fungal concentrations in indoor air were less than 10³ cfu m⁻³ and a large proportion of them was collected in Stage-2 of the Andersen sampler. Moreover, the ratio between indoor and outdoor concentrations was <3:1. Five of the 30 sampled homes yielded >500 cfu m⁻³ of one genus, with up to 1493Cladosporium cfu m⁻³ or 2549Penicillium cfu m⁻³. Also, these two genera were predominant in both airborne and settled dust, and their concentrations were greater indoors than out, indicating a possible indoor source of fungal propagules. The predominant species wereCladosporium herbarum, Penicillium aurantiogriseum andP. chrysogenum. These results suggest that exposure to large concentrations of fungi occurs indoors and is associated with both seasons of the year and with particular home characteristics.     

(1 → 3)-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucan in different background environments and seasons

This study was undertaken to investigate how the length of the extraction period influences the (1 → 3)-β-d-glucan (β-glucan) yield and also to examine the background concentration of β-glucan as airborne β-glucan in outdoor environments in different seasons and as concentrations in airborne and floor dust in offices. To ensure compatibility between results obtained in different laboratories, it is important to use optimal and standardised methods to extract and quantify β-glucan. In this study, an extraction period of 60 min gave the highest β-glucan yield. The median concentration of β-glucan in 44 floor dust samples was 597 μg g⁻¹ dust. The median concentration of airborne β-glucan in offices was 5.1 ng m⁻³ in the summer and 2.3 ng m⁻³ in the winter, and the outdoor median concentration in towns was 6.8 ng m⁻³. The outdoor airborne concentration of β-glucan was significantly lower in January, November and December than during the rest of year. In July, the median airborne concentration of β-glucan was 14 times higher than in January. Furthermore, the airborne concentration of β-glucan was significantly higher in July than in March, April, May, September and October. In the summertime, we found that the indoor airborne concentration of β-glucan was lower than outdoor concentrations. This is in accordance with measurements of concentrations of airborne pollen and culturable fungal spores showing higher outdoor than indoor concentrations during the summer months.     

Relevance of bacterioplankton abundance and production in the oligotrophic equatorial Indian Ocean

Bacterioplankton abundance and production, chlorophyll a (Chl a) concentrations and primary production (PP) were measured from the equatorial Indian Ocean (EIO) during northeast (NEM), southwest (SWM) and spring intermonsoon (SpIM) seasons from 1°N to 5°S along 83°E. The average bacterial abundance was 0.52 ± 0.29, 0.62 ± 0.33 and 0.46 ± 0.19 (× 10⁸ cells l⁻¹), respectively during NEM, SWM and SpIM in the top 100 m. In the deep waters (200 m and below), the bacterial counts averaged ∼0.35 ± 0.14 × 10⁸ cells l⁻¹ in SWM and 0.39 ± 0.16 × 10⁸ cells l⁻¹ in SpIM. The 0–120 m column integrated bacterial production (BP) ranged from 19 to 115 and from 10 to 51 mg C m⁻² d⁻¹ during NEM and SWM, respectively. Compared with many open ocean locations, bacterial abundance and production in this region are lower. The bacterial carbon production, however, is notably higher than that of phytoplankton PP (BP:PP ratio 102% in SWM and 188% in NEM). With perpetually low PP (NEM: 20, SWM: 18 and SpIM: 12 mg C m⁻² d⁻¹) and Chl a concentration (NEM: 16.5, SWM: 15.0 and SpIM: 20.9 mg m⁻²), the observed bacterial abundance and production are pivotal in the trophodynamics of the EIO. Efficient assimilation and mineralization of available organics by bacteria in the euphotic zone might serve a dual role in the ultra-oligotrophic regions including EIO. Thus, bacteria probably sustain microheterotrophs (micro- and meso-zooplankton) through microbial loop. Further, rapid mineralization by bacteria will make essential nutrients available to autotrophs.     

Aerobic heterotrophic bacteria and petroleum-utilizing bacteria from cow dung and poultry manure

In this study, enumeration and identification of total aerobic heterotrophic bacteria and petroleum-utilizing bacteria as well as the degradative potential of petroleum-utilizing bacterial isolates were carried out. The average counts of total aerobic heterotrophic bacteria in cow dung and poultry manure were 74.25 × 10⁵ c.f.u. g⁻¹ and 138.75 × 10⁵ c.f.u. g⁻¹ respectively. Acinetobacter sp, Bacillus sp, Pseudomonas sp, and Serratia spp. occurred as aerobic heterotrophs in both cow dung and poultry manure. However, Alcaligenes spp. occurred only in cow dung while, Flavobacterium sp, Klebsiella sp, Micrococcus sp, and Nocardia spp. occurred only in poultry manure as aerobic heterotrophs. The average counts of petroleum-utilizing bacteria in cow dung and poultry manure were 9.25 × 10⁵ c.f.u. g⁻¹ and 17.25 × 10⁵ c.f.u. g⁻¹ respectively. Pseudomonas spp. occurred as petroleum utilizer in both cow dung and poultry manure. However, Bacillus spp. occurred only in cow dung while Acinetobacter spp. and Micrococcus spp. occurred only in poultry manure as petroleum utilizers. Relative abundance of petroleum utilizers in total aerobic heterotrophs ranged from 6.38% to 20.00% for cow dung and from 9.38% to 17.29% for poultry manure. Introduction of pure cultures of petroleum-utilizing bacteria from cow dung and poultry manure into sterile oil-polluted soil revealed oil degradation in one week period.     

A heat shock following electroporation induces highly efficient transformation of Corynebacterium glutamicum with xenogeneic plasmid DNA

An improved method for the electrotransformation of wild-type Corynebacterium glutamicum (ATCC 13032) is described. The two crucial alterations to previously developed methods are: cultivation of cells used for electrotransformation at 18 °C instead of 30 °C, and application of a heat shock immediately following electrotransformation. Cells cultivated at sub optimal temperature have a 100-fold improved transformation efficiency (10⁸ cfu μg⁻¹) for syngeneic DNA (DNA isolated from the same species). A heat shock applied to these cells following electroporation improved the transformation efficiency for xenogeneic DNA (DNA isolated from a different species). In combination, low cultivation temperature and heat shock act synergistically and increased the transformation efficiency by four orders of magnitude to 2.5 × 10⁶ cfu μg⁻¹ xenogeneic DNA. The method was used to generate gene disruptions in C. glutamicum. Received: 26 March 1999 / Received revision: 9 June 1999 / Accepted: 11 June 1999