Microbial fouling community analysis of the cooling water system of a nuclear test reactor with emphasis on sulphate reducing bacteria

Culture and molecular-based techniques were used to characterize bacterial diversity in the cooling water system of a fast breeder test reactor (FBTR). Techniques were selected for special emphasis on sulphate-reducing bacteria (SRB). Water samples from different locations of the FBTR cooling water system, in addition to biofilm scrapings from carbon steel coupons and a control SRB sample were characterized. Whole genome extraction of the water samples and SRB diversity by group specific primers were analysed using nested PCR and denaturing gradient gel electrophoresis (DGGE). The results of the bacterial assay in the cooling water showed that the total culturable bacteria (TCB) ranged from 10³ to 10⁵ cfu ml^?1; iron-reducing bacteria, 10³ to 10⁵ cfu ml^?1; iron oxidizing bacteria, 10² to 10³ cfu ml^?1 and SRB, 2–29 cfu ml^?1. However, the counts of the various bacterial types in the biofilm sample were 2–3 orders of magnitude higher. SRB diversity by the nested PCR-DGGE approach showed the presence of groups 1, 5 and 6 in the FBTR cooling water system; however, groups 2, 3 and 4 were not detected. The study demonstrated that the PCR protocol influenced the results of the diversity analysis. The paper further discusses the microbiota of the cooling water system and its relevance in biofouling.     

Evaluation of water corrosion,scaling extent and heterotrophic plate count bacteria in asbestos and polyethylene pipes in drinking water distribution system

Corrosion and scaling is one of the most important factors influencing drinking water quality that cause health disorders and economic problems. The aim of this study was to evaluate these phenomena in two sources of surface (Makou city) and ground water (Khoy city) in water networks. Corrosion and scaling potential was surveyed by Langelier, Ryzener, aggressiveness, Larson and Puckorius Indices and with measuring water physical, chemical, and microbial parameters. Statistical paired samples t-test displayed significant difference in means value of Langelier, Ryzener, Puckorius indices between cold and warm seasons of the year in Khoy samples and significant difference in means value of Ryzener, Puckorius and aggressiveness indices between cold and warm seasons of the year in Makou samples (p-value <0.001). Heterotrophic plate count water samples investigated in two cold and hot seasons in Khoy were respectively 14 ± 16 cfu ml^?1 and 41 ± 26 cfu ml^?1 and in the town of Makou were 11 ± 7 cfu ml^?1 and 61 ± 29 cfu ml^?1, respectively. In terms of health impacts, corrosion in different mains is important, then providing proper measures for balancing water quality before entering to the network and substituting of mains to prevent economic and health problems are necessary.     

Fermentation of wheat: Effects of backslopping different proportions of pre-fermented wheat on the microbialand chemical composition

Abstract

The objective of the study was to examine effect of backslop on the chemical and microbiological characteristics of fermented wheat (FW). Coarsely ground wheat was mixed with water (1:3 wt/wt) and inoculated with 6 log cfu ml^?1 each of an overnight culture of Lactobacillus plantarum and Pediococcus pentosaceus. Four fermentation treatments were conducted in 45 l, closed, PVC containers over 48 hours. Three treatments investigated the benefits of the addition of previously fermented wheat (backslopping, BSL) at different proportions (0.20, 0.33 or 0.42 kg) to freshly prepared wheat. The control treatment contained no addition of BSL. Elimination of coliforms from the FW within 48 h was only achieved through backslopping; where coliform bacteria counts decreased from approximately 6.5 log₁₀ cfu ml^?1 to less than 3 log₁₀ cfu ml^?1. There was no apparent advantage in increasing the backslop proportion above 0.20. However, the exclusion of coliform bacteria required the pH to remain below 4.0 for at a minimum of 24 h. The results of these studies indicate that fermentation of wheat has the potential to reduce the risk of feed-borne colibacillosis and provides a practical alternative to producers that cannot ferment multiple diets or have limited fermentation capacity.     

Decreasing Enterobacter sakazakii (Cronobacter spp.) food contamination level with bacteriophages: prospects and problems

Enterobacter sakazakii (Cronobacter spp.) is an opportunistic pathogen, which can cause rare, but life‐threatening infections in neonates and infants through feeding of a contaminated milk formula. We isolated 67 phages from environmental samples and tested their lytic host range on a representative collection of 40 E. sakazakii strains. A cocktail of five phages prevented the outgrowth of 35 out of 40 test strains in artificially contaminated infant formula. Two E. sakazakii phages represented prolate head Myoviridae. Molecular tests identified them as close relatives of Escherichia coli phage T4. The remaining three phages represented isometric head Myoviridae with large genome size of 140 and 200 kb, respectively, which belonged to two different DNA hybridization groups. A high dose of 10⁸ pfu ml^?1 of phage could effectively sterilize a broth contaminated with both high and low pathogen counts (10⁶ and 10² cfu ml^?1). In contrast, broth inoculated with 10⁴ phage and 10² bacteria per ml first showed normal bacterial growth until reaching a cell titre of 10⁵ cfu ml^?1. Only when crossing this threshold, phage replication started, but it could not reduce the contamination level below 100 cfu ml^?1. Phages could be produced with titres of 10¹⁰ pfu ml^?1 in broth culture, but they were not stable upon freeze‐drying. Addition of trehalose or milk formula stabilized the phage preparation, which then showed excellent storage stability even at elevated temperature.     

Improvement of the production of 5-methoxypodophyllotoxin using a new selected root culture of Linum flavum L.

Differences in transformation of the tomato cultivar (Ohio 7870, Roma, UCD82b) by wild-type Agrobacterium strains (A6, A66, A281) were identified in a leaf disk assay system. Transformation was expressed as the percentage of explants producing callus on hormone-free medium and was confirmed by opine production. Ohio 7870 and Roma were more readily transformed than UCD82b by all three strains of A. tumefaciens. Cotyledons and older true leaves of all three cultivars were more readily transformed than younger leaves. Transformation was biphasic over the bacterial concentrations tested (2×10³–7×10⁹ colony forming units ml^-1; cfu ml^-1) for all cultivars and leaf ages, and was greatest at 5×10⁸ cfu ml^-1. Transformation decreased significantly at levels less than 2×10⁷ cfu ml^-1 and slightly at concentrations higher than 5×10⁸ cfu ml^-1. UCD82b tissue was more necrotic than Ohio 7870 or Roma after incubation with bacteria, which may account for reduced transformation of this cultivar.     

Biofilm formation on brass coupons exposed to a cooling system of an oil refinery

Brass coupons (70% Cu 30% Zn) were exposed to a cooling freshwater system of an oil refinery, in order to investigate susceptibility of the metal to biofilm formation. The coupons were fixed on bypasses at points which allowed the circulation of makeup, cooling and return water. The number of aerobic, anaerobic and sulfate-reducing bacteria was determined in both the planktonic and the sessile phases. Maximum bacterial concentrations were detected in the cooling water, corresponding to 2.1 ± 0.1 × 10⁶ CFU ml⁻¹ (planktonic phase) and 1.3 ± 0.2 × 10⁵ CFU cm⁻² (sessile phase) for aerobic bacteria and to 3.2 ± 0.3 × 10⁵ cells ml⁻¹ (planktonic phase) and 6.2 ± 0.7 × 10⁵ cells cm⁻² (sessile phase) for anaerobic bacteria. Sulfate-reducing bacteria (SRB) were observed only in the planktonic phase, being found in greater numbers in the return water. Scanning electron microscopy (SEM) analysis indicated that biofilm formation occurred at the three monitored sites and showed a diversity in cell morphology. Nonetheless, no evidence of corrosion was observed on the brass coupons during the experimental period. Received 22 May 1997/ Accepted in revised form 19 September 1997     

Quantitative and specific detection of the biocontrol agent, Serratia plymuthica, in plant extracts using a real-time TaqMan? assay

A Serratia plymuthica-specific TaqMan? assay was designed based on the consensus nucleotide sequence from the 3??- end of the luxS gene present in all S. plymuthica strains tested. The specificity of the assay was demonstrated by testing 21 Serratia spp. strains and 30 isolates belonging to various species that can potentially coexist with S. plymuthica in the same environment. Positive reactions in the TaqMan? assay were observed only for S. plymuthica isolates and not for other bacteria. The TaqMan? assay could detect down to 1.95 ng of S. plymuthica DNA, down to 5 bacterial cells per reaction (100?cfu ml^?1) in vitro, down to 50 bacterial cells per reaction (1,000?cfu ml^?1) in spiked potato root extracts and down to 5 bacterial cells per reaction (100?cfu ml^?1) in spiked potato haulm extracts. We used this assay to quantify S. plymuthica A30 cells in potato and tomato haulms and roots grown from S. plymuthica A30-inoculated potato seed tubers and tomato seeds. The results were comparable with the spread-plating of plant extracts on a newly developed S. plymuthica A30 selective medium (CVTR2Arif). The TaqMan? assay can be used to quantify S. plymuthica isolates in different ecosystems and in complex substrates.     

The corrosion behaviour of galvanized steel in cooling tower water containing a biocide and a corrosion inhibitor

The corrosion behaviour of galvanized steel in cooling tower water containing a biocide and a corrosion inhibitor was investigated over a 10-month period in a hotel. Planktonic and sessile numbers of sulphate reducing bacteria (SRB) and heterotrophic bacteria were monitored. The corrosion rate was determined by the weight loss method. The corrosion products were analyzed by energy dispersive X-ray spectroscopy and X-ray diffraction. A mineralized, heterogeneous biofilm was observed on the coupons. Although a biocide and a corrosion inhibitor were regularly added to the cooling water, the results showed that microorganisms, such as SRB in the mixed species biofilm, caused corrosion of galvanized steel. It was observed that Zn layers on the test coupons were completely depleted after 3?months. The Fe concentrations in the biofilm showed significant correlations with the weight loss and carbohydrate concentration (respectively, p?<?0.01 and p?<?0.01).     

Biodiversity and extracellular enzymatic activity of heterotrophic bacterial communities in Bardawil Lagoon,Egypt

The biodiversity of heterotrophic viable bacteria (209 isolates) in the hypersaline Bardawil Lagoon, Egypt, was studied. Composition and extracellular activities of viable culturable heterotrophic bacteria (VCHB) in the water and in non-colonised and seagrass-colonised sediments of Bardawil Lagoon were determined bimonthly during 1997 and 1998. The average ± SD total Kjeldhal nitrogen was 1.69 ± 0.44 mg l^?1 in water, 335.95 ± 19.22 mg kg^?1 in colonised sediments, and 215.5 ± 16.0 mg kg^?1 in non-colonised sediments. Exoenzymatic bacterial activity (glycosidase) presented a seasonal trend with average values of 1.02 ±0.16 μM cm^?3 min^?1 in colonised sediment samples and was 0.36 ± 0.27 μM cm^?3 min^?1 in non-colonised sediments. Mean of VCHB was 4 017 ± 565 cfu g^?1 and 1 195 ± 242 cfu g^?1 for colonised and non-colonised sediments, respectively. Bacterial isolates from Bardawil Lagoon water and sediments yielded a wide diversity of VCHB: a total of 209 different species, belonging to 13 genera from the water and 12 genera from the sediments.     

Studies on production of alcoholic beverages from some tropical fruits

The varieties of alcoholic beverages from watermelon; watermelon-banana and watermelon-pineapple mixtures were produced by using monoculture and mixed culture fermentation techniques. Three yeast species, namely, Saccharomyces cerevisiae, Kleochera apicalata, Torulospora delbruckii and four bacterial species Leuconostoc oenos, Lactobacillus Sp, Micrococcus luteus and Streptococcus lactis were identified during the study. The daily succession of these organisms in the various fermenting samples differed in cell mass and occurrence due to their different growth conditions and factors present. A higher bacterial load (3.9 ± 0.2-4.4 ± 0.3) log (cfu) ml^?1 than yeast (2.8 ± 00-4.6 ± 0.4) log (cfu) ml^?1 counts was observed in the mixed culture fermentation, while in the monoculture fermentation, a higher yeast load (4.3 ± 0.3-4.7 ± 0.2) log (cfu) ml^?1 than bacterial loads (2.7 ± 0.1-4.1 ± 0.3) log (cfu) ml^?1 counts was recovered. The results obtained from the present study indicated that monoculture-fermented beverages were of better quality as compared to the mixed culture fermented ones. The monoculture-fermented beverage from watermelon-pineapple mixture was ranked as the best alcoholic beverage based on sensory evaluation score.     

Determination of lactic acid bacteria producing biogenic amines in wine by quantitative PCR methods

Aims: To develop rapid methods allowing enumeration of lactic acid bacteria producing biogenic amines in wines and to analyse wine samples by the methods. Methods and Results: Methods based on quantitative PCR targeting bacterial genes involved in histamine, tyramine and putrescine production were developed and applied to detect and quantify the bacteria producing these biogenic amines in wine. Analysis of 102 samples revealed low populations of the targeted bacteria in grape must samples, an increased bacteria biomass in wine samples after alcoholic fermentation, reaching the highest population levels (above 10⁶ cells ml^?1) during spontaneous malolactic fermentation. A minimum of 10³ ml^?1 producing cells was required for production of more than 1 mg l^?1 of biogenic amines. Accumulation of putrescine in wine was correlated with the presence of bacteria carrying an ornithine decarboxylation pathway. Trials of winemaking showed that the use of selected bacteria for inducing malolactic fermentation was efficient to limit the proliferation of undesirable bacteria and the production of biogenic amines. Conclusion: Methods using quantitative PCR are efficient to enumerate biogenic amines‐producing cells in wine. Significance and Impact of the Study: The methods can help to better control and to improve winemaking conditions in order to avoid biogenic amine production.     

Formate Oxidation-Driven Calcium Carbonate Precipitation by Methylocystis parvus OBBP

Microbially induced carbonate precipitation (MICP) applied in the construction industry poses several disadvantages such as ammonia release to the air and nitric acid production. An alternative MICP from calcium formate by Methylocystis parvus OBBP is presented here to overcome these disadvantages. To induce calcium carbonate precipitation, M. parvus was incubated at different calcium formate concentrations and starting culture densities. Up to 91.4% ± 1.6% of the initial calcium was precipitated in the methane-amended cultures compared to 35.1% ± 11.9% when methane was not added. Because the bacteria could only utilize methane for growth, higher culture densities and subsequently calcium removals were exhibited in the cultures when methane was added. A higher calcium carbonate precipitate yield was obtained when higher culture densities were used but not necessarily when more calcium formate was added. This was mainly due to salt inhibition of the bacterial activity at a high calcium formate concentration. A maximum 0.67 ± 0.03 g of CaCO₃ g of Ca(CHOOH)₂⁻¹ calcium carbonate precipitate yield was obtained when a culture of 10⁹ cells ml⁻¹ and 5 g of calcium formate liter⁻¹ were used. Compared to the current strategy employing biogenic urea degradation as the basis for MICP, our approach presents significant improvements in the environmental sustainability of the application in the construction industry.     

Corrosion of Iron by Iodide-Oxidizing Bacteria Isolated from Brine in an Iodine Production Facility

Elemental iodine is produced in Japan from underground brine (fossil salt water). Carbon steel pipes in an iodine production facility at Chiba, Japan, for brine conveyance were found to corrode more rapidly than those in other facilities. The corroding activity of iodide-containing brine from the facility was examined by immersing carbon steel coupons in “native” and “filter-sterilized” brine samples. The dissolution of iron from the coupons immersed in native brine was threefold to fourfold higher than that in the filter-sterilized brine. Denaturing gradient gel electrophoresis analyses revealed that iodide-oxidizing bacteria (IOBs) were predominant in the coupon-containing native brine samples. IOBs were also detected in a corrosion deposit on the inner surface of a corroded pipe. These results strongly suggested the involvement of IOBs in the corrosion of the carbon steel pipes. Of the six bacterial strains isolated from a brine sample, four were capable of oxidizing iodide ion (I^?) into molecular iodine (I₂), and these strains were further phylogenetically classified into two groups. The iron-corroding activity of each of the isolates from the two groups was examined. Both strains corroded iron in the presence of potassium iodide in a concentration-dependent manner. This is the first report providing direct evidence that IOBs are involved in iron corrosion. Further, possible mechanisms by which IOBs corrode iron are discussed.     

Characterization of glycolipid biosurfactant from Pseudomonas aeruginosa CPCL isolated from petroleum‐contaminated soil

Aims: To isolate and characterize the biosurfactant‐producing micro‐organism from petroleum‐contaminated soil as well as to determine the biochemical properties of the biosurfactant. Methods and Results: A novel rhamnolipid‐producing Pseudomonas aeruginosa (GenBank accession number GQ241355 ) strain was isolated from a petroleum‐contaminated soil. Surface active compound was separated by solvent extraction of the acidified culture supernatant. The extract was able to reduce the surface tension of water from 72 to 44 mN m^?1 at a critical micelle concentration of 11·27 ± 1·85 mg l^?1. It showed better activity (based on microdilution method) against Gram‐positive (≤ 31 mg ml^?1) bacteria and filamentous fungi (≤ 50 mg ml^?1) than Gram‐negative bacteria (≥ 125 mg ml^?1) with mild toxicity (HC₅₀– 38 ± 8·22 μg ml^?1) to red blood cells. Fourier transform infrared spectroscopy revealed the presence of aliphatic chain, hydroxyl groups, ester and glycosidic bonds. Presence of nineteen rhamnolipid homologues with variation in chain length and saturation was revealed from liquid chromatography coupled to mass spectrometry with electrospray ionization. Conclusion: The results indicate that the isolated biosurfactant has a novel combination of rhamnolipid congeners with unique properties. Significance and Impact of the Study: This study provides a biosurfactant, which can be used as a biocontrol agent against phytopathogens (Fusarium proliferatum NCIM 1105 and Aspergillus niger NCIM 596) and exploited for biomedical applications.     

Isolation of antifouling compounds from the marine bacterium, <Emphasis Type="Italic">Shewanella oneidensis</Emphasis> SCH0402

Two compounds, 2-hydroxymyristic acid (HMA) and cis-9-oleic acid (COA), were isolated from a chloroform extract of the marine bacterium, Shewanella oneidensis SCH0402. In a spectrophotometer-based chemotaxis assay, HMA completely eliminated the optical density (OD) of Alteromonas marina SCH0401 and Bacillus atrophaeus SCH0408, motile, fouling bacteria, at 100 and 1000 μg ml⁻¹, respectively. COA similarly decreased the OD of A. marina and B. atrophaeus by 100% at 1000 μg ml⁻¹. The commercially available, highly toxic anti-fouling compound, tributyltin oxide (TBTO) never reduced the OD of the target bacteria by 100% even at higher concentration. Instead, all the test bacterial cells were killed at higher than 1000 μg ml⁻¹ of concentration. Both HMA and COA inhibited germination of Ulva pertusa spores completely at 10 and 100 μg ml⁻¹, respectively, while TBTO inhibited germination at 0.01 μg ml⁻¹. However, in field assays, both HMA and COA showed anti-fouling activities as potent as TBTO against a wide range of fouling organisms, including micro- and macro-algae, barnacles, and mussels. The average fouling coverage on the surface of the control panel was 93 ± 6% after 1.5 years but no fouling was observed on the surface of the test panel onto which each compound was applied separately. Thus, bacterial repellent compounds can be used as substitutes for potent toxic anti-fouling compounds, resulting in higher standards of environmental safety without loss of anti-fouling performance.     

Vertical distribution in and isolation of bacteria from Lake Vanda: an Antarctic lake

Vertical distribution of bacteria in Lake Vanda, an Antarctic meromictic lake, was examined by the acridine orange epifluorescence direct count method. Total bacteria were 10⁴–10⁵ cells · ml^–1 in the water at 55 m depth and above, and increased drastically to 10⁷ cells · ml^–1 in the bottom water. Filamentous or long rodshaped bacteria occurred at a high frequency in the upper layers, but in the bottom layers most bacteria were coccoidal or short rods. Mean bacterial cell volume in water of between 10 m and 60 m deep was fairly large compared with common bacterial populations in seawater and lake water. Aerobic heterotrophic bacteria were recovered from the water of a depth of 30 m and above, and were assumed to belong to Caulobacter. Viable heterotrophic bacteria were not recovered from the high salinity deep water by media prepared with the same deep water. Phototrophic purple non-sulphur bacteria were isolated by enrichment cultures from water at 55 m depth.     

New approach to use ethidium bromide monoazide as an analytical tool

Aims: Ethidium bromide monoazide (EMA) has been determined to cause delay in DNA amplification from dead bacteria at real‐time PCR. However, there is concern that the increasing EMA concentration to suppress amplification from high number of dead bacteria also affects live bacteria. The aim is to disclose a novel application of EMA for food hygienic test. Methods and Results: We performed a low‐dose double EMA treatment. Live or heat‐dead Enterobacter sakazakii (reclassified as Cronobacter spp.) in 10% powdered infant formula (PIF) solution was subjected to a treatment with 20 μg ml^?1 of EMA followed by a treatment with 10 μg ml^?1 of EMA without washing, and direct real‐time PCR. We observed that DNA amplification from 10⁷ cells ml^?1 of dead Ent. sakazakii was completely suppressed within 50 cycles of PCR, whereas 10²–10³ cells ml^?1 of viable cells could be detected. When a 3‐h enrichment step in liquid medium was included after the first EMA treatment, live Ent. sakazakii could be detected at initial levels of 10⁰–10² cells ml^?1. We compared the low‐dose double‐treated EMA‐PCR with the culture method using 80 samples of PIF, and completely correlative results were obtained for both methods. Conclusions: We concluded that the newly developed low‐dose double‐treated EMA‐PCR is a very effective tool for live Ent. sakazakii detection in PIF. Significance and Impact of the Study: We focused on the specific nature of photoreactive compound that residual EMA is cancelled by irradiation. We were successful in treating bacteria with EMA in gradient concentration to increase live and dead distinction ability.     

Molecular Detection of Anaerobic Ammonium-Oxidizing (Anammox) Bacteria in High-Temperature Petroleum Reservoirs

Anaerobic ammonium-oxidizing (anammox) process plays an important role in the nitrogen cycle of the worldwide anoxic and mesophilic habitats. Recently, the existence and activity of anammox bacteria have been detected in some thermophilic environments, but their existence in the geothermal subterranean oil reservoirs is still not reported. This study investigated the abundance, distribution and functional diversity of anammox bacteria in nine out of 17 high-temperature oil reservoirs by molecular ecology analysis. High concentration (5.31–39.2 mg l^?1) of ammonium was detected in the production water from these oilfields with temperatures between 55°C and 75°C. Both 16S rRNA and hzo molecular biomarkers indicated the occurrence of anammox bacteria in nine out of 17 samples. Most of 16S rRNA gene phylotypes are closely related to the known anammox bacterial genera Candidatus Brocadia, Candidatus Kuenenia, Candidatus Scalindua, and Candidatus Jettenia, while hzo gene phylotypes are closely related to the genera Candidatus Anammoxoglobus, Candidatus Kuenenia, Candidatus Scalindua, and Candidatus Jettenia. The total bacterial and anammox bacterial densities were 6.4?±?0.5?×?10³ to 2.0?±?0.18?×?10⁶ cells ml^?1 and 6.6?±?0.51?×?10² to 4.9?±?0.36?×?10⁴ cell ml^?1, respectively. The cluster I of 16S rRNA gene sequences showed distant identity (<92%) to the known Candidatus Scalindua species, inferring this cluster of anammox bacteria to be a new species, and a tentative name Candidatus “Scalindua sinooilfield” was proposed. The results extended the existence of anammox bacteria to the high-temperature oil reservoirs.     

The effect of butenolide on behavioral and morphological changes in two marine fouling species,the barnacle Balanus amphitrite and the bryozoan Bugula neritina

Butenolide [5-octylfuran-2(5H)-one] is a very promising antifouling compound. Here, the effects of butenolide on larval behavior and histology are compared in two major fouling organisms, viz. cypris larvae of Balanus amphitrite and swimming larvae of Bugula neritina. Butenolide diminished the positive phototactic behavior of B. amphitrite (EC₅₀ = 0.82 μg ml^?1) and B. neritina (EC₅₀ = 3 μg ml^?1). Its effect on the attachment of cyprids of B. amphitrite was influenced by temperature, and butenolide increased attachment of larvae of B. neritina to the bottom of the experimental wells. At concentrations of 4 μg ml^?1 and 10 μg ml^?1, butenolide decreased attachment of B. amphitrite and B. neritina, respectively, but the effects were reversible within a certain treatment time. Morphologically, butenolide inhibited the swelling of secretory granules and altered the rough endoplasmic reticulum (RER) in the cement gland of B. amphitrite cyprids. In B. neritina swimming larvae, butenolide reduced the number of secretory granules in the pyriform-glandular complex.     

Algae,bacteria and detritus as food for the harpacticoid copepod, Heteropsyllus pseudonunni Coull and Palmer

The harpacticoid copepod, Heteropsyllus pseudonunni Coull and Palmer, when fed Juncus roemerianus Scheele (needlerush) detritus produced significantly more eggs than when fed the alga Dunaliella sp. Five food rations and a starved control were used: A, algal concentration ≈ 10⁴ cells · ml^?1; LA, algal concentration 10³ cells · ml^?1; D, detritus concentration 0.25 g · ml^?1; LD, detritus concentration 0.025 g · ml^?1; LDLA, a mixture of the LD and LA rations. Geometric mean total egg production values were: LDLA 132.5; LD 132.6; D 120.5; A 65.8; LA 5.0. The LA results were significantly less (P = 0.05; Student-Newman-Keuls' test) than all others, while the A results were significantly less than the LDLA, LD and D results. The LDLA, LD and D results were not statistically different. Similar trends were obtained when mean brood sizes and mean number of broods were compared. In a second feeding experiment, using Juncus detritus, bacteria on sand grains, and algae (Nitzschia sp.) on sand grains, Heteropsyllus pseudonunni produced significantly more eggs (P = 0.05; SNK test) when fed detritus (166.0) or bacteria (132.2) than algae (58.9). The detritus and bacteria results were not significantly different.