Quantitative Assessment of Factors Affecting the Recovery of Indigenous and Released Thermophilic Bacteria from Compost

Thermophilic actinomycetes and bacilli were recovered from mushroom compost by conventional dilution plating and sedimentation chamber-Andersen sampler methods. Excessive growth of thermophilic bacilli on dilution plates accounted for the poor recovery and limited diversity of actinomycete colonies, and this result was largely unaffected by the use of modified extraction procedures and diluents. Assessment of the actinomycete population was more successfully achieved by applying the sedimentation chamber method, by using selective media, or both. Background resistance of the compost microflora to selective agents (kanamycin, novobiocin, tetracycline, thiostrepton, and NaCl) was extremely varied, but both actinomycetes and bacilli were particularly sensitive to tetracycline. The selective isolation of Thermoactinomyces spp. and Thermomonospora chromogena by novobiocin and kanamycin, respectively, was shown to be reproducible, and the use of high concentrations of kanamycin resulted in the isolation of a novel group of unidentified thermophilic actinomycetes. Comparison of nonselective nutrient media demonstrated that the nutrient-rich protoplast regeneration medium R5 was surprisingly efficient for actinomycete recovery. This medium was found to be particularly appropriate for the recovery of Saccharomonospora viridis BD125, introduced as spores into both sterile and fresh samples of mushroom compost. This stable pigmented variant of the S. viridis strains indigenous to compost was released at concentrations of up to 10⁷ spores g of compost⁻¹ in order to provide information for future experiments on the release and recovery of genetically manipulated strains. The detection limits for this strain were in the region of 10² g⁻¹ from sterilized compost but only 10⁵ g⁻¹ from nonsterile compost. These figures correspond to mean recovery efficiencies of approximately 70% (sterilized compost) and 53% (fresh compost) of viable spores released. Further improvements in the detection and recovery of S. viridis strains released into compost should be achieved by the introduction of selectable markers developed from this information on the antibiotic resistance profile of the indigenous compost microflora.     

Distribution of clinically important thermophilic actinomycetes in vegetable substrates and soil in north-western India

Medically important thermophilic actinomycetes were isolated from 218 (64%) of 341 samples of vegetable substrates and soil examined from sites in north-western India. Thermoactinomyces vulgaris (T. candidus) was the commonest species, occurring in 56% of samples, followed by Saccharomonospora viridis in 29%, Thermoactinomyces thalpophilus in 27%, Faenia rectivirgula (Micropolyspora faeni) in 21% and Thermoactinomyces sacchari in 14%. T. vulgaris and T. thalpophilus were isolated from all types of substrate examined, with T. vulgaris always more common than T. thalpophilus. Of the other thermophilic actinomycetes, F. rectivirgula was isolated predominantly from hay (44%) and S. viridis (56%) and T. sacchari (44%) from sugarcane bagasse. The largest populations of T. vulgaris and T. thalpophilus were found in paddy straw, followed by T. sacchari, S. viridis and F. rectivirgula in sugar-cane bagasse.The widespread occurrence of these clinically important thermophilic actinomycetes suggests that exposure of humans and animals to them may be frequent in north-western India. Studies are required to determine the prevalence of extrinsic allergic alveolitis (hypersensitivity pneumonitis) caused by thermophilic actinomycetes in the local population.     

Occurrence and significance of precipitating antibodies against thermophilic actinomycetes in the sera of dairy herd workers,Nangali, Delhi

The study was prompted by the lack of information on the role of thermophilic actinomycetes in hypersensitivity pneumonitis in India. It reports the occurrence of precipitating antibodies against clinically important thermophilic actinomycetes in the sera of a population sample of dairy herd workers, Nangali, Delhi. Of 112 workers investigated, 28 (25%) showed precipitins againstFaenia rectivirgula, 4 (3.2%) againstSaccharomonospora viridis, 2 againstThermoactinomyces thalpophilus and one each againstT. vulgaris andT. sacchari. The results of enzyme-linked immunosorbent assay (ELISA) indicated that IgG antibody activity againstF. rectivirgula was significantly higher in the symptomatic group than in the asymptomatic group (p<0.05) of workers and the controls (p<0.01). Significant difference inF. rectivirgula IgG activity was also obtained between the precipitin-positive symptomatic group and the precipitin-positive asymptomatic group (p< 0.05). In strong contrast, the IgG antibody activity againstT. thalpophilus was found to be uniformly low. A limited aeromicrobiological sampling of the dairy farm revealedS. viridis (55.8%) to be the commonest species followed byT. vulgaris (19.2%),T. thalpophilus (18.5%),F. rectivirgula (5%) andT. sacchari (15%). On the basis of suggestive clinical and laboratory findings, farmer's lung disease was suspected in four dairy herd workers. A comprehensive clinical evaluation including pulmonary function studies on the dairy herd workers and their long-term follow-up is indicated to determine the extent of respiratory morbidity caused byF. rectivirgula, S. viridis, T. thalpophilus, T. sacchari andT. vulgaris in India.     

Occurrence of thermophilic actinomycetes in natural substrates in Nigeria

Thermophilic actinomycetes were isolated from 163 (48.95%) of 333 samples of vegetable substrates and soil from different sites in Anambra and Enugu States in Nigeria.Thermoactinomyces (Tha.) vulgaris was the most common, occurring in 32.4% of samples whileTha. thalpophilus was isolated from 20.1%.Tha. sacchari, Saccharomonospora (Sam.) viridis andSaccharopolyspora (Sap.) rectivirgula were isolated from 3–10.5% of the samples examined.Streptomyces (Stm.) thermovulgaris occurred in 2.7% andThermomonospora spp. in 0.6% of samples. Except forStm. thermovulgaris and, perhaps,Thermomonospora spp., all the species isolated are known to be allergenic in man. The five known allergenic species were abundant in hay and maize silage.T. vulgaris andT. thalpophilus were also frequently isolated from rice straw.Tha. vulgaris, Tha. thalpophilus andSap. rectivirgula were all most numerous in hay whileTha. sacchari was most numerous in maize silage. The widespread occurrence of thermophilic actinomycetes in Nigeria emphasizes the need for investigation of their role in allergic respiratory disorders.     

Structures of the tetrahydrogenated menaquinones fromActinomadura angiospora,Faenia rectivirgula,andSaccharothrix australiensis

The structures of the tetrahydrogenated menaquinones fromActinomadura angiospora, Faenia rectivirgula, andSaccharothrix australiensis were determined by mass spectrometry and proton nuclear magnetic resonance spectrometry. The positions of saturation of the tetrahydrogenated menaquinones fromFaenia rectivirgula andSaccharothrix australiensis were units II plus III (counting from the ring system), whereas that ofActinomadura angiospora had units III and VIII hydrogenated. The tetrahydrogenated menaquinones fromFaenia rectivirgula andSaccharothrix australiensis are similar to those characterized from other Gram-positive taxa to date, whereas that fromActinomadura angiospora represents a hitherto unknown isomer.     

An airborne actinobacteria Nocardiopsis alba isolated from bioaerosol of a mushroom compost facility

Actinobacteria are widely distributed in many environments and represent the most important trigger to the occupant respiratory health. Health complaints, including hypersensitivity pneumonitis of the workers, were recorded in a mushroom compost facility (MCF). The studies on the airborne bacteria were carried out to find a possible microbiological source of these symptoms. Culture analysis of compost bioaerosols collected in different location of the MCF was performed. An assessment of the indoor microbial exposure revealed bacterial flora of bioaerosol in the mushroom compost facility represented by Bacillus, Geobacillus, Micrococcus, Pseudomonas, Staphylococcus spp., and actinobacterial strain with white aerial mycelium. The thermotolerant actinobacterial strain of the same morphology was repeatedly isolated from many locations in MCF: air, compost sample, and solid surface in production hall. On the base of complex morphological, chemotaxonomic, and phylogenetic characteristics, the isolate has been classified as Nocardiopsis alba. Dominant position of N. alba in microbial environment of the mushroom compost facility may represent an indicator microorganism in compost bioaerosol. The bioavailability of N. alba in mushroom compost facility creates potential risk for the health of workers, and the protection of respiratory tract and/or skin is strongly recommended.     

Mushroom worker's lung: Serologic reactions to thermophilic actinomycetes present in the air of compost tunnels

Vast numbers of spores of the thermophilic actinomycetesExcellospora flexuosa,Thermomonospora alba,T. curvata andT. fusca were collected from the air in fermentation tunnels during the spawning of mushroom compost, i.e. over 10⁹ CFU m^–3 of air. Five different genera of fungi, namely,Aspergillus,Aureobasidium,Cladosporium,Penicillium andScytalidium, were found at only 10³ CFU m^–3 of air.Agaricus bisporus, used for spawning, was absent. Sera of 10 mushroom growers affected by Mushroom Worker's Lung (MWL) were tested by a qualitative dot-ELISA for antibodies against the spores of these micro-organisms. All 10 were positive for one or more of the actinomycetesE. flexuosa,T. alba,T. curvata andT. fusca. No antibodies were found againstStreptomyces thermovulgaris,Thermoactinomyces vulgaris andT. sacchari nor against the fungiAspergillus fumigatus,Penicillium brevicompactum,P. chrysogenum,Scytalidium thermophilum andTrichoderma viride. Sera of 11 of 14 workers engaged in routine spawning of compost in tunnels reacted positively with 1 or more of the actinomycetes. Their¹⁰log serum titres increased with the duration of employment to an upper limit of 2.5. The sera of 19 non-exposed individuals were negative. Because high numbers of spores ofE. flexuosa,T. alba,T. curvata andT. fusca were present in the air that was used for successful inhalation provocation of mushroom workers with MWL and because of the elevated serum titres of these workers, we presume these organisms to contribute in the occurrence of MWL.     

Evaluation of bio-aerosols at an animal feed manufacturing industry: A case study

Both total and biological particles (totalculturable bacteria, Gram negative bacteria,mold and actinomycetes) were measured at ananimal feed manufacturing industry. Suspendedparticle concentration ranged from 1.72 to2.3 mg m^–3 with a mean value of1.97 mg m^–3. Airborne microorganisms weredetected in lower concentrations than thoseassociated with suspended dust andfeed-materials. Bacterial concentrations weretwo to three times higher than concentrationsof mold and actinomycetes. Bacterialconcentrations averaged4.86 × 10³ cfu m^–3; 2.6 × 10⁴cfu m^–3 and 3.96 × 10⁷ cfu g^–1 inair, associated with suspended dust andfeed-materials, respectively, whereas moldconcentrations averaged 7.33 × 10²cfu m^–3; 1.97 × 10³ cfu m^–3 and7 × 10⁵ cfu g^–1 of the correspondingenvironments, respectively. Enterobacterspp and Klebsiella spp were the mostabundant Gram negative bacteria, whereas Bacillus species. were the most dominant Grampositive bacteria. Aspergllius niger,other Aspergillus species and Penicillium were the dominant mold isolates.Acremonium was only detected in feedmaterials, whereas Aspergillus fumigatuswas only detected in air. The animal feedindustry environment has a significantbio-contamination and many of microorganismsimplicated in respiratory problems weredetected in this environment.     

Simple emission-reducing measures in an open biological waste treatment plant

In the course of composting biological waste, concentrations of various thermophilic and thermotolerant microorganisms increase. Moving piles of compost results in increased emissions of Actinomycetes and fungi. The present investigation deals with the reduction of airborne microorganism emission and immission in large-scale composting plants with open piles. Simple measures were introduced in order to reduce the release of bioaerosols when turning piles and the release of dust and bioaerols at large. These measures included the sealing of turning machinery with rubber mats, the wetting of piles before and after turning and regular cleaning and wetting driveways during the dry season.Concentrations of airborne microorganisms during the summer season were determined on 5 days before and after the introduction of emission-reducing measures using the six-stage Andersen cascade sampler. The investigation showed that following the introduction of emission-reducing measures there was, at all locations, a highly significant reduction not only of all culturable indicator organisms (thermophilic actinomycetes and Aspergillus fumigatus) but also of total microorganism concentrations (p < 0,001). The introduction of the simple emission-reducing measures mentioned above, however, reduced the immission in the vicinity of the plant to such a degree that the natural background levels were reached at a distance of 150 m.     

Grape marc compost: microbial studies and suppression of soil-borne mycosis in vegetable seedlings

Compost suppression of soil-borne diseases in horticultural crops has been attributed to the activities of antagonistic microorganisms. A great diversity of microorganisms, capable of suppressing pathogens naturally colonize compost. A large number of microbes appeared in microbiological analyses of grape marc compost. Most microorganisms were bacteria. Average percentages were 31% mesophilic and 28% thermophylic bacteria, 16% mesophilic actinomycetes and 20% thermophylic actinomycetes. Only a few mould and yeast morphologies were obtained, 4% and 1% respectively. Antagonist in vitro assays were performed with 432 microbial morphologies isolated from grape marc compost. The microbes isolated were extremely effective antagonists in in vitro assays against all the fungal pathogens tested. Seven microorganisms were selected for further bioassay with Rhizoctonia solani in radish, Fusarium oxysporum f. sp. radicis-cucumerinum in melon, and Phytophthora parasitica in tomato and two microorganisms with Pythium aphanidermatum in cucumber. Those experiments indicate that grape marc compost reduces the severity of Pythium damping-off in cucumber, but does not reduce the severity of Phytophthora root rot in tomato, Fusarium oxysporum f. sp. radicis-cucumerinum in melon and Rhizoctonia solani in radish. Better suppressive effects were not demonstrated by either compost or vermiculite amended with microbes selected from grape marc compost.     

The microbiology of moist barley storage in unsealed silos

The microflora of moist barley grain and whole-crop barley silage stored in top-unloading, unsealed concrete-staved silos on six farms in England depended on the initial water content of the grain (23–58%), method of covering the grain, and the rate at which it was unloaded. Fungi and actinomycetes were fewest when the initial water content was more than 30%, and the grain was covered first with a layer of wilted grass, and then a plastic sheet. During unloading, the uppermost layer of grain remained in good condition provided 7.5 cm was removed daily. With an inefficient top-seal, the top grain heated and became mouldy, as it also did when unloading was slow. As the rate of unloading slowed, heating increased, and a characteristic succession of fungi and actinomycetes developed. With unloading at 7.5 cm/day or more, only yeasts, chiefly Endomycopsis chodatii Wickerham and Hansenula anomala (Hansen) H. & P. Sydow, were abundant, but at slightly slower rates of unloading Penicillium spp. also became common. Both these groups became less common as unloading was slowed further and were replaced, first by Absidia spp. and Mucor pusillus Lindt, then Aspergillus fumigatus Fres., Humicola lanuginosa (Griffon & Maublanc) Bunce, Micropolyspora faeni Cross, Maciver & Lacey, and Thermoactinomyces vulgaris Tsiklinsky as the heating increased. The number of spores (including bacterial cells) that could be removed from samples by blowing air ranged from 0.4–428 times 10⁶/g dry weight of grain. Whole-crop barley silage contained 2.9–132 times 10⁶spores/g dry weight. Similar species were isolated from whole-crop silage as from grain. Little moulding occurred deeper than 30 cm below surface of the grain. Concentrations of airborne spores were estimated periodically during two seasons. There were always more airborne spores than is usual in outdoor air. Without disturbance the silos contained 10⁶-10⁷ spores/m³ air, but when mouldy grain was unloaded concentrations increased to a maximum of 2860times10⁶ spores/m³ air; more than half of these were bacteria and actinomycetes and a quarter Aspergillus flavus Link. Potentially pathogenic fungi and actinomycetes were frequent, particularly when they also occurred in the grain or capping materials for spontaneous heating. Some probably survived in dust deposits and were resuspended during unloading. Airborne spores were frequent around the silos when grain was unloaded and rolled. Workers should wear efficient dust respirators at these times and while inside silos.     

Improved medium for recovery and enumeration of the farmer's lung organism, Saccharomonospora viridis.

A new medium, which we propose to call R8, was developed for the isolation and enumeration of the thermophilic actinomycete, Saccharomonospora viridis. This organism has been implicated in a range of hypersensitivity pneumonitides, including farmer's lung, but is generally isolated in small numbers from contaminated environments. Recovery of S. viridis from moldy hay and mushroom compost on R8 medium was compared with recovery on conventional media. S. viridis was isolated from both substrates but in highest numbers and most consistently on the R8 medium. The selectivity of this medium was best observed when the sedimentation chamber method was used for hay samples. Here S. viridis accounted for up to 80% of the total number of actinomycetes recovered on R8 and could not be recovered on rifampin selective medium under the same conditions. R8 was also found to be an efficient recovery medium for a range of thermophilic actinomycetes from mushroom compost and for another allergenic species, Faenia rectivirgula, from moldy hay. Contamination of isolation plates by thermophilic bacilli was reduced on R8 compared with the activity on half-strength tryptone soy agar, supplemented with 0.2% casein hydrolysate, and this, together with specific improvements in S. viridis growth, accounts for the selective effect. It is possible that the occurrence of S. viridis and its role as a causative agent of hypersensitivity pnuemonitis have been underestimated by the use of suboptimal recovery protocols. It is hoped that use of R8 in conjunction with dilution plate techniques will generate information on the ecology of S. viridis and contribute to health risk assessment studies.     

Relative Numbers of Certain Microbial Groups Present in Compost Used for Mushroom (Agaricus bisporus) Propagation

The relative numbers of microorganisms associated with compost during mushroom production were studied by the dilution plate method. Thermophilic actinomycetes and fungi were isolated with a very high frequency early in the growing season. Although numbers of thermophilic bacteria diminished slowly during the season, the thermophilic fungi and actinomycetes diminished rapidly with the latter disappearing after 6 weeks. Mesophilic fungi other than Agaricus or Trichoderma remained relatively stable throughout the growing period. Agaricus could be isolated between the first and third break. Trichoderma became dominant after the fourth break. The mesophilic bacterial counts diminished during the most productive portion of the mushroom cropping season and then increased to much higher numbers toward the end of the season.     

Airborne pollen and spores’ deposition in alveolar tissues as a tool in drowning forensic diagnosis

We report the results of a histological study of lung samples where an unusual quantity of airborne pollen and fungal spores was found in drowned rats. Pollen and spores were found in lungs of drowned rats but not in the post-mortem submerged ones. Another control group consisting of rats that underwent 60 min exposure to a highly pollen-loaded atmosphere also recorded negative for the presence of pollen or fungal spores. Pollen types coincided with plants growing at the surrounding gardens flowering during the days of the experiment, performed during spring, that were detected by the aerobiological trap located at the city. The pollen observed at the lower airways’ tissues were Chenopodiaceae, Cupressus, Ericaceae, Jasminum, Olea europaea, Plantago, Pinus, Poaceae, Quercus and Urticaceae. Regarding fungal spores Alternaria, Aspergillus, Cladosporium cladosporoides, Cladosporium herbarum, Leptosphaeria, Polythrincium and Phitomyces. Pollen and spores’ penetration into deeper regions of the respiratory tract is an unusual phenomenon not happening in regular breathing conditions. Our results revealed that these particles appeared in a significant number in lung samples of drowned animals probably pushed down from upper airways by the force of water inhalation during drowning. Their presence into alveolar spaces offer a useful forensic evidence in doubtful drowning autopsies, favoured by the characteristic of the sporopollenin (pollen wall) and chitin (fungal spore wall) resistance. Moreover, the presence of these particles in alveoli areas of drowned bodies can help forensics to obtain information about pre-mortem dates and places.

     

Improved medium for recovery and enumeration of the farmer's lung organism, Saccharomonospora viridis

A new medium, which we propose to call R8, was developed for the isolation and enumeration of the thermophilic actinomycete, Saccharomonospora viridis. This organism has been implicated in a range of hypersensitivity pneumonitides, including farmer's lung, but is generally isolated in small numbers from contaminated environments. Recovery of S. viridis from moldy hay and mushroom compost on R8 medium was compared with recovery on conventional media. S. viridis was isolated from both substrates but in highest numbers and most consistently on the R8 medium. The selectivity of this medium was best observed when the sedimentation chamber method was used for hay samples. Here S. viridis accounted for up to 80% of the total number of actinomycetes recovered on R8 and could not be recovered on rifampin selective medium under the same conditions. R8 was also found to be an efficient recovery medium for a range of thermophilic actinomycetes from mushroom compost and for another allergenic species, Faenia rectivirgula, from moldy hay. Contamination of isolation plates by thermophilic bacilli was reduced on R8 compared with the activity on half-strength tryptone soy agar, supplemented with 0.2% casein hydrolysate, and this, together with specific improvements in S. viridis growth, accounts for the selective effect. It is possible that the occurrence of S. viridis and its role as a causative agent of hypersensitivity pnuemonitis have been underestimated by the use of suboptimal recovery protocols. It is hoped that use of R8 in conjunction with dilution plate techniques will generate information on the ecology of S. viridis and contribute to health risk assessment studies.     

Bioaerosol emissions in a poultry litter burning plant

This study investigates the exposure of workers to biological particles in a poultry litter burning plant in operation. The microorganism concentrations were examined at different workplaces during procedures leading to increased emissions. The concentrations of culturable airborne mesophilic, xerophilic and thermophilic microorganisms in the ambient air were tested inside and outside of the burning plant using two different methods of measuring. The focus of this study was on the quantitative evaluation of culturable bacteria as well as the quantitative and qualitative evaluation of gram-negative bacteria, fungi and thermophilic actinomycetes. The maximum airborne concentrations were found in the delivery hall. Mesophilic bacteria concentrations reached up to 1.7 × 10⁶ CFU/m³; gram-negative bacteria up to 9.1 × 10² CFU/m³. Fungal propagule concentrations for xerophilic fungi were between 1.2 × 10³ and 2.9 × 10⁴ CFU/m³ and for mesophilic fungi between 4.4 × 10² and 2.9 × 10⁴ CFU/m³. Among fungi, Aspergillus niger, Eurotium herbariorum and Scopulariopsis brevicaulis species were dominant. Thermophilic actinomycetes reached airborne concentrations of 8.7 × 10⁴ CFU/m³, with increased concentrations of the pathogens causing extrinsic allergic alveolitis. The high concentrations of airborne microorganisms in poultry litter burning plants and the potential hazard of the intake of microorganisms including potential pathogens require the introduction of consistent measures in both technical areas and personnel management.     

Performance of olive mill solid waste as a constituent of the substrate in commercial cultivation of Agaricus bisporus

The feasibility of using olive mill waste (OMW) as an ingredient in the substrate used for cultivation of Agaricus bisporus (Lange) Sing. was studied in a large-scale cultivation trial, concerning 2500 m² of mushroom growing area, at a specialized mushroom farm. Standard commercial cultivation technique involving compost preparation, spawning, casing and harvesting was used. The performance indicators such as mushroom yield, biological efficiency, market quality as well as horticultural value of the spent compost showed that the compost prepared with OMW was superior to the control compost in all the categories. The OMW-amended substrate supported higher populations of beneficial microorganisms especially, actinomycetes which enabled the breakdown of the compost ingredients. It is suggested that OMW is a suitable ingredient for the preparation of mushroom substrate. We have demonstrated that conversion of OMW (a liability) into value-added mushroom substrate (an asset) is an effective waste management tool in oleaculture.     

Microbial degradation of poly-β-hydroxybutyrate using landfill soils

The population of poly-β-hydroxybutyrate-degrading microorganisms and the biodegradation of PHB in local landfill soils were examined in vitro and in vivo. Forty-two PHB-degraders consisting of 12 bacteria, 25 actinomycetes and 5 moulds were isolated. The total PHB-degraders averaged 4.7 × 10⁷ and 20 × 10⁴ colony forming units (cfu)/g for San Mateo wet and dry soils, respectively, and 2.3 × 10⁷ and 8.5 × 10⁴ cfu/g for Carmona wet and dry samples, respectively. The PHB-degraders formed 0–59% of the total microbial population in San Mateo and 8–42% in Carmona. Complete (100%) degradation of PHB powder was observed for Chryseomonas-27 and Aspergillus-39 on day 5 in shake flask culture and for Streptomyces-4 on day 7. Burial test in landfill soils showed a 90–91% weight loss of PHB film strips within four weeks; the weight loss of polypropylene film strips was up to 0.12% only. Scanning electron micrographs of degraded films revealed the attachment of microbial cells and fungal mycelium and spores on the surfaces. Holes and cavities were also noted due to the microbial degradation processes.     

Moulding of sugar-cane bagasse and its prevention

When fresh sugar-cane bagasse containing about 50% water and 3% sugar was baled and stacked, it quickly heated to over 50°C and remained hotter than 40°C for 50 days. The residual sucrose was utilized by microbial growth and the content of fungal, bacterial and actinomycete spores increased to more than 10⁸/g dry wt. The spores in heated bagasse were mostly of thermophilic actinomycetes and fungi, and included two actinomycetes implicated in bagassosis. Thermoactinomycetes sacchari occurred in 40% of samples examined, some of which yielded up to 5 × 10⁶ colonies/g, while T. vulgaris occurred in 80% of samples, but these rarely yielded more than 10⁵ colonies/g. Other organisms were cellulolytic and caused fibre deterioration. Heating and moulding could be much decreased either by drying to about 25% water content, which halved the spore content after storage, mostly at the expense of the actinomycetes, or by adding 2% by weight of propionic acid, which decreased the spore content to 4 × 10⁶ spores/g or less even after 18 months' storage. Sometimes adding only 0·6% of propionic acid or 2% of propionic acid applied as a 50% aqueous solution had a similar effect. Treatment with propionic acid thus decreased the deterioration of bagasse, permitted its storage between harvests and prevented the hazard of bagassosis to workers.     

Bacterial species in raw and cured compost from a large-scale urban composter

Summary Raw and cured compost samples from a large-scale urban composter were studied over a period of eight months to gain information on bacterial species present. Total viable, aerobic heterotrophic bacteria, lactose-positive bacteria, antibiotic and metal-resistant bacteria and thermophilic bacteria were enumerated. Both raw and cured compost samples contained metal and antibiotic-tolerant bacteria (–1 compost) as well as high numbers (as high as Log 7.4 CFU g^–1 dry weight compost) of thermophilic bacteria isolated by growth at 55 °C. Selected colonies were also identified using the Biolog 95 substrate identification system.Escherichia coli andSalmonella spp. were not detected in compost samples.