Total Plate Count Of Bacteria Research Articles

Reducing Total Plate Count of Bacteria through Dark Sealed Storage for Plant Factory Nutrient Solution Sterilization

Plant factories are efficient systems for vegetable production under a clean and controlled environment. To improve the sterilization efficiency of nutrient solutions (NS) in plant factories, this study examined the changes in the number and composition of colonies from in-use and post-use stored NS. The sterilization effect under ultraviolet (UV) light-emitting diode light was also investigated. The results indicated that the total plate count of bacteria (TPC) of newly prepared NS was 3.99 lg CFU/mL (9870 CFU/mL); within 7 days of cultivation, this number sharply increased ∼7.8 times to 4.88 lg CFU/mL (76,000 CFU/mL), then remained stable. After dark sealed storage (DSS) of post-use NS, TPC dramatically decreased by 82.8% and reached its lowest point at 4.29 lg CFU/mL (19,566 CFU/mL) on day 3, equivalent to a log survival ratio of −0.76, then rapidly rebounded by 235.6% to 4.82 lg CFU/mL (65,666 CFU/mL) on day 4. During storage, bacterial community composition was also remarkably changed, and the relative abundance of heterotrophic bacteria such as Variovorax paradoxus and Pararhizobium giardinii and photosynthetic bacteria such as Pseudo-Nitzschia multiseries were greatly decreased. The log survival ratio for in-use and post-use stored NS under UV sterilization were −1.29 and −1.30, respectively, and was not significantly different. Coupled with the dramatic decrease in TPC during DSS, the overall log survival ratio of post-use NS UV sterilization was −2.06 and was the most effectively form of sterilization in our study. In short, TPC of in-use NS remained high for a long period, and DSS may serve as a low-cost NS sterilization method in plant factories.

THE ROLE OF NISIN, POTASSIUM SORBATE AND SODIUM LACTATE AS ADDITIVE IN IMPROVING THE CHEMICAL AND QUALITATIVE CHARACTERISTICS OF CHILLED GROUND BEEF.

This study was conducted to evaluate the effects of nisin, potassium sorbate and sodium lactate and their interactions as preservatives in fat oxidation, some quality and microbial characteristics of chilled ground beef meat stored at 4C˚ for 0,4,8 and 12 days. The study included nine different treatments: T1 (control treatment without addition), T2 (nisin at a concentration of 150 mg/kg), T3 (potassium sorbate 0.075 g/kg), T4 (sodium lactate 3%), T5 (nisin 150 mg/kg + potassium sorbate 0.075 g/kg), T6 (nisin 150 mg/kg + sodium lactate 3%), T7 (Sodium Lactate 3% + Potassium Sorbate 0.075 g/kg), T8 (Nisin 150 mg/kg + Sodium Lactate 3% + Potassium Sorbate 0.075 g/kg) and T9 (Addition of Butylated hydroxyanisole(BHA 0.01%)). All treatments showed significant (p<0.01) decreases in dry matter percentage of (fat and ash) and increase in protein and moisture and water holding capacity (WHC) percentage as compared with the control treatment at any refrigerated storage time. Thiobarbituric acid (TBA) were lower (P<0.01) in nisin, potassium sorbate and sodium lactate treatments when compared with the control treatment at any refrigerated storage time. Nisin, potassium sorbate and sodium lactate treated samples reduced (P<0.01) the total plate count of bacteria during refrigerated storage times. It can be concluded that nisin, potassium sorbate and sodium lactate had positive significant influence on quality characteristics and microbial safety of ground beef meat when stored under refrigeration at 4C° up to 12 days.

Quality of farmed shrimp (Penaeus monodon, Fabricius, 1798 and Macrobrachium rosenbergii, deman, 1879) as affected by melanosis inhibiting compounds

A problem associated with shrimp is blackspot or melanosis and to prevent blackspot, sulfites have been used for years but come with additional health risks. Newer 4- hexylresorcinol formulations exist that allow sulfite-free shrimp, but effects on the quality of Penaeus monodon Fabricius, 1798, and Macrobrachium rosenbergii, de Man, 1879, beyond melanosis prevention are unknown. Adverse effects on the quality of the shrimp from melanosis prevention treatments would negatively offset the benefits of a sulfite-free product. In order to determine if prevention compounds (sulfite powder or 4- hexylresorcinol based compounds, Everfresh® and Xyrex® Prawnfresh™) affect quality, proximate composition and total plate count of bacteria were determined for cultured (P. monodon and M. rosenbergii) shrimp in Bangladesh. The results showed no effect of melanosis prevention compound on proximate composition (p > 0.05), but for each parameter, species were significantly different (p < 0.001). For total plate count, treatment was not significantly different (p = 0.09), but species were significantly different in total plate count (p < 0.001). M. rosenbergii had a higher total plate count. Results of this study indicated that proximate composition and bacterial levels are not affected by 4- hexylresorcinol melanosis treatments. Melanosis prevention is necessary to reduce loss due to unacceptance, and 4-hexylresorcinoltreated shrimp can provide the industry with a sulfite-free alternative.

Microbiological Quality of Nuts, Dried and Candied Fruits, Including the Prevalence of Cronobacter spp.

Cronobacter genus bacteria are food-borne pathogens. Foods contaminated with Cronobacter spp. may pose a risk to infants or immunocompromised adults. The aim of this study was to determine the microbiological quality of nuts, seeds and dried fruits with special emphasis on the occurrence of Cronobacter spp. Analyses were carried out on 64 samples of commercial nuts (20 samples), dried fruits (24), candied fruits (8), seeds (4), and mixes of seeds, dried fruits and nuts (8). The samples were tested for the total plate count of bacteria (TPC), counts of yeasts and molds, and the occurrence of Cronobacter spp. Cronobacter isolates were identified and differentiated by PCR-RFLP (Polymerase Chain Reaction - Restriction Fragments Length Polymorphism) and RAPD-PCR (Random Amplified Polymorphic DNA by PCR) analysis. TPC, and yeasts and molds were not detected in 0.1 g of 23.4%, 89.1%, and 32.8% of the analyzed samples. In the remaining samples, TPC were in the range of 1.2–5.3 log CFU g−1. The presence/absence of Cronobacter species was detected in 12 (18.8%) samples of: nuts (10 samples), and mixes (2 samples). The 12 strains of Cronobacter spp. included: C. sakazakii (3 strains), C. malonaticus (5), and C. turicensis (4). The results of this study contribute to the determination of the presence and species identification of Cronobacter spp. in products of plant origin intended for direct consumption.

Bottled water brands are contaminated with multidrug resistant bacteria in Nairobi, Kenya

Background: The demand for drinking water has necessitated the proliferation of bottled water companies in Kenya. This study evaluated if retailed bottled water in Nairobi Kenya complies with both local and international reference criteria. Methods: A total of 42 different water brands (25 approved by Kenya Revenue Authority (KRA) and 17 banned brands) were analyzed for both physicochemical and bacteriological quality. The spread plate method was used to obtain the total plate count of bacteria, while the membrane filter method was used to obtain total coliform count (TCC) and fecal coliform count (FCC). Structured interviews were used to gather company-related information. Results: Overall, 16% of KRA-approved and 35.3% of banned bottled water were contaminated with heterotrophic bacteria. Of the approved water brands, 4% were positive for total coliforms, compared with 17% of the banned brands. Similarly, 4% and 17% approved and banned water brands were positive for fecal coliforms, respectively. Escherichia coli (19.1%), Pseudomonas spp. (9.5%) and Klebsiella spp. (4.8%) were the most common bacterial types isolated from all water brands, most of which exhibited multidrug resistance. In multivariable analysis, water companies that cleaned pipework and bottles using chlorine-based disinfectants (OR 0.08, 95% CI 0.01 to 0.8), those that had food safety programs (OR 0.1, 95% CI 0.019 to 0.9), had standard operating procedures (SOP) for water sourcing (OR 0.1, 95% CI 0.012 to 0.9) and SOP for contamination protection (OR 0.1, 95% CI 0.02 to 0.9) remained independently associated with bottled water brands exceeding WHO TCC limits. Conclusions: A number of bottled water brands were contaminated with one or more types of indicator bacteria, some of which were multidrug-resistant. Water bottling companies’ processes contribute to contamination. Rigorous regulation and monitoring will improve water quality and safety.

Bottled water brands are contaminated with multidrug resistant bacteria in Nairobi, Kenya

Background: The demand for drinking water has necessitated the proliferation of bottled water companies in Kenya. This study evaluated if retailed bottled water in Nairobi Kenya complies with both local and international reference criteria. Methods: A total of 42 different water brands (25 approved by Kenya Revenue Authority (KRA) and 17 banned brands) were analyzed for both physicochemical and bacteriological quality. The spread plate method was used to obtain the total plate count of bacteria, while the membrane filter method was used to obtain total coliform count (TCC) and fecal coliform count (FCC). Structured interviews were used to gather company-related information. Results: Overall, 16% of KRA-approved and 35.3% of banned bottled water were contaminated with heterotrophic bacteria. Of the approved water brands, 4% were positive for total coliforms, compared with 17% of the banned brands. Similarly, 4% and 17% approved and banned water brands were positive for fecal coliforms, respectively. Escherichia coli (19.1%), Pseudomonas spp. (9.5%) and Klebsiella spp. (4.8%) were the most common bacterial types isolated from all water brands, most of which exhibited multidrug resistance. In multivariable analysis, water companies that cleaned pipework and bottles using chlorine-based disinfectants (OR 0.08, 95% CI 0.01 to 0.8), those that had food safety programs (OR 0.1, 95% CI 0.019 to 0.9), had standard operating procedures (SOP) for water sourcing (OR 0.1, 95% CI 0.012 to 0.9) and SOP for contamination protection (OR 0.1, 95% CI 0.02 to 0.9) remained independently associated with bottled water brands exceeding WHO TCC limits. Conclusions: A number of bottled water brands were contaminated with one or more types of indicator bacteria, some of which were multidrug-resistant. Water bottling companies’ processes contribute to contamination. Rigorous regulation and monitoring will improve water quality and safety.

Dietary Lipid:Protein Ratio and n-3 Long-Chain Polyunsaturated Fatty Acids Alters the Gut Microbiome of Atlantic Salmon Under Hypoxic and Normoxic Conditions.

Researchers have adjusted dietary lipid:protein ratios and n-3 long-chain polyunsaturated fatty acids (LC-PUFA) to optimize the growth performance of Atlantic salmon. However, dietary impacts on the gut microbiome are lacking, especially under varying environmental conditions. To examine this response, post-smolt salmon (184 ± 5 g) were fed diets with lipid:protein ratios considered low (180, 570 g/kg) and high (230, 460 g/kg) along with low and high levels of n-3 LC-PUFA (7 or 14 g/kg) while fish were reared under low and high levels of dissolved oxygen (6.7 or 8.0 mg/L). At day 0, 35 and 116, digesta in the distal intestine were collected and analyzed for viable counts and 16S ribosomal RNA (rRNA) genes (V4 region) using Illumina MiSeq. The reduction in oxygen had negligible effects, except on viable plate counts of total bacteria and an initial effect on beta-diversity. In contrast, the high lipid (HL) diets had an increased alpha-diversity (e.g., Shannon and Chao-1) at day 0 and day 35 whereas high n-3 diets suppressed these indices at day 116. Generally, a reduction in alpha-diversity was observed over time and an interaction between lipid:protein ratio x n-3 was found. Between diets, beta-diversity and phyla abundance were similar as both Proteobacteria (44%) and Firmicutes (21%) dominated. However, at the genus level Aliivibrio, Streptococcus, Weissella, and Lactobacillus, were associated with low lipid (LL) diets while the high lipid diets were associated with less abundant bacteria, e.g., Chromohalobacter. At day 116, the relative abundance of the Tenericutes phylum increased 10-fold (36%). Fish fed the high lipid diet with high n-3 had reduced alpha-diversity, lowest abundance of lactic acid bacteria, and highest abundance of Mycoplasma, which may indicate a less healthy gut microbiome. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis revealed that saturated and unsaturated fatty acid biosynthesis pathways were several folds higher in fish fed the high lipid diet, possibly to compensate for the lack of dietary n-3. In summary, our results show that the viable plate counts, alpha-diversity, beta-diversity, and predictive function of gut bacteria in Atlantic salmon post-smolts are influenced by dietary lipid:protein ratio and n-3 LC-PUFA over several time points with little effect by dissolved oxygen.

Bottled water brands are contaminated with multidrug resistant bacteria which are associated with companies handling procedures in Nairobi, Kenya.

Background: The demand for water has necessitated the proliferation of bottled water companies in Kenya. This study evaluated if retailed bottled water in Nairobi Kenya complies with both local and international reference criteria. Methods: A total of 42 different water brands (25 approved by Kenya Revenue Authority (KRA) and 17 banned brands) were analyzed for both physicochemical and bacteriological quality. Spread plate method was used to obtain the total plate count of bacteria, while the membrane filter method was used to obtain total coliform count (TCC) and fecal coliform count (FCC). Structured interviews were used to gather company-related information. Results: Overall, 16% of KRA-approved and 35.3% of banned bottled water were contaminated with heterotrophic bacteria. Of the approved water brands, 4% were positive for total coliforms, compared with 17% of the banned brands. Similarly, 4% and 17% approved and banned water brands were positive for fecal coliforms, respectively. Escherichia coli (19.1%), Pseudomonas spp. (9.5%) and Klebsiella spp. (4.8%) were the most common bacterial types isolated from all water brands, most of which exhibited multidrug resistance. In multivariable analysis, water companies that cleaned pipework and bottles using chlorine-based disinfectants (OR 0.08, 95% CI 0.01 to 0.8), those that had food safety programs (OR 0.1, 95% CI 0.019 to 0.9), had standard operating procedures (SOP) for water sourcing (OR 0.1, 95% CI 0.012 to 0.9) and SOP for contamination protection (OR 0.1, 95% CI 0.02 to 0.9) remained independently associated with bottled water brands exceeding WHO TCC limits. Conclusions: A number of bottled water brands were contaminated with one or more types of indicator bacteria, some of which were multidrug resistant. Water bottling companies' processes contribute to contamination; rigorous regulation and monitoring will improve on water quality and safety.

Antibiotic sensitivity of bacteria associated with selected waste dumpsites in Akure, Nigeria

A study was carried out to determine the antibiotic sensitivity pattern of bacteria isolates associated with selected waste dumpsites in Akure metropolis, Nigeria. Results revealed that the total plate count of bacteria ranged from 1.3×105 cfu/g to 3.0×106 cfu/g. Bacillus subtilis, Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi, Streptococcus faecalis, Shigella dysenteriae, Escherichia coli, Micrococcus luteus, Serratia marcescens, Clostridium botulinum were the isolated bacterial species. The temperature and pH values ranged from 26˚C to 28˚C and 5.68 to 6.48 respectively. Pseudomonas aeruginosa and Serratia showed susceptibility to antibiotics while Micrococcus luteus exhibited resistance to the antibiotics. Some of these isolated bacteria are pathogenic and thus, poses potential threat to the local inhabitant of the area. Therefore, proper waste management practices must be put in place to avoid environmental health hazards.
 Keywords: bacteria, dumpsites, antibiotic, waste management, environmental health

Effect of nitrogen nanobubble preservation on the quality, microbial population, and storage life of fresh yellowfin tuna (Thunnus albacares)

The objectives of this study were to evaluate the effect of nitrogen nanobubble for storing fresh yellowfin tuna (Thunnus albacares). Yellowfin tuna were stored for 10 days in two types of treatment: nitrogen nanobubble (NNB) and conventional packaging process (CPC). Two methods including qualitative (organoleptic) and quantitative (histamine and mercury content, and total plate count of bacteria) were analyzed to determine the treatments effect on post-harvest quality, microbial population, and shelf-life of the fish. Results show that nitrogen nanobubble is proven to maintain dissolved oxygen levels remain in low conditions ( < 1 mg/L) during treatment. Although the organoleptic properties for both treatments do not show any significant differences, the lowest histamine and mercury contents are found in treatment NNB at 11.8 mg/kg and 0.14 mg/kg, respectively. The microbes in treatment NNB is achieved levels deemed safe (based on national standards) at 1.8 × 104 colonies/g, E. coli content <3 MPN/g, and the presence of Salmonella sp. are not detected. Our results suggest that treatment NNB is preferable for preservation process of fresh yellowfin tuna and might improve to extend the shelf-life.

Single and combined effects of tea polyphenols and edible chitosan coating on the shelf life improvement of refrigerated dagger-tooth pike conger (Muraenesox cinereus)

ABSTRACT In China, the preservation of refrigerated daggertooth piker congers (Muraenesox cinereus) has received increasing attention in recent years due to the increased demand for fresh congers. In this study, the effect of tea polyphenols (0.1%, 0.2%, 0.4%) and chitosan (0.5%, 1%, 2%) on daggertooth piker conger preservation was evaluated based on major spoilage bacteria detected during cold storage. The preservation quality was assessed through sensory scores, TVB-N, and TBARS concentrations and plate counts of total bacteria, H2S-producing bacteria, and Pseudomonas. The results showed that all concentrations of tea polyphenols and chitosan successfully inhibited spoilage bacterial growth, suppressed TVB-N (total volatile basic nitrogen) and TBARS (thiobarbituric acid-reactive substances) generation, and improved the sensory score, although the results were not dose-dependent. The optimal concentrations of tea polyphenols and chitosan were 0.2% and 0.5%, respectively. A later assessment of the synergistic effect of tea polyphenols and chitosan coating conger samples with both preservatives at their optimal concentration. Possibly, due to their mechanic difference in bacteriostasis, the combined treatment significantly inhibited the growth of H2S-producing bacteria and Pseudomonas, indicating a better antibacterial effect than when using one of the preservatives alone. Finally, combined tea polyphenol and chitosan treatment prolonged the first- and second-grade freshness of refrigerated congers for 4–6 days.

The effect of edible coating contained Kecombrang leaves concentrate on gourami fish fillet quality

Gourami fillet is fishery product that perishable and has short shelf life. To prolongs its shelf life, the application of edible coating could be performed. Edible coating is a thin layer that covers food products and serves as a protector against mass transfer (such as moisture, oxygen, light, lipids, and solutes) and as an additive carrier. Kecombrang contains bioactive compounds that act as antimicrobials. This study was aimed to know the effect of concentration addition of Kecombrang leaves concentrate to gourami fillet quality during storage at ±4°C. The experimental design used was Randomized Complete Design. The treatments were concentration of added concentrate of Kecombrang leaves (K) at amount of 1% (K1), 2% (K2), 3% (K3), and 4% (K4). The results showed that the application of edible coating contained Kecombrang leaves concentrates at concentration of 4% on gourami fillets showed best results according to color intensity, pH, free fatty acid content, and the total plate count of bacteria.

PERHITUNGAN ANGKA LEMPENG TOTAL BAKTERI PADA TELUR AYAM RAS

Poultry farm chicken eggs is one of the favorite food for society besides meat and fish, because it is highly nutritious, versatile and cheaper than other eggs. The sample of this research uses 8 (eight) samples of poultry farm chicken eggs. This study aims to determine the quality of poultry farm chicken eggs microbiology based on the total plate count of bacteria. The results showed average the total plate count of bacteria on 8 chicken eggs is 104 CFU/ml. This shows that the results still qualified the standard defined by BPOM that is 107 CFU/ml and its mean poultry farm chicken eggs is safe for consumption.&#x0D; &#x0D; Keywords: Poultry farm chicken eggs, Total Plate Count of Bacteria

PENGARUH PENCELUPAN KARKAS AYAM PEDAGING DALAM LARUTAN ASAM SITRAT DAN ASAM ASETAT TERHADAP ANGKA LEMPENG TOTAL Escherichia coli (The Immersion Effect of Broiler Carcass in Citric Acid and Acetic Acid on the Total Plates Count of Escherichia Coli)

This study aimed to determine the immersion effect of broiler carcasses in 3% citric acid, 3% acetic acid, and combination of citric acid and acetic acid with concentration of 1.5% each on the total plate count of bacteria E. coli. Eight broilers carcasses (dissected into 2 parts) were divided into 4 treatment groups with 2 times repetition and 3 times observation at 0, 4, and 8 hours after dipped. The control treatment (K0) without dipped into acid solution. Broiler carcasses in the first (K1), second (K2), and the third (K3) treatments were dipped into 3% acetic acid, 3% citric acid, and combination of 1.5% acetic acid and 1.5% citric acid respectively. Data were analyzed using analysis of variance. The average of E. coli count in K0 at 0, 4, and 8 hours post dipping were 5.2±0.061, 6.8±0.99, and 7.0±0.107 log 10 cfu/g of chicken meat respectively. In similar observation time with K0, the average of total E. coli count were 5.5±0.373, 6.0±0.023, and 6.0±0.242 log 10 cfu/g of chicken meat in K1, 5.3±0.166, 6.0±0.143, and 6.0±0.084 log 10 cfu/g of chicken meat in K2, 5.7±0.041, 5.9±0.92, and 5.8±0.058 log 10 cfu/g of chicken meat in K3 at 0,4, and 8 hours post dipping respectively. Statistical analysis showed that the immersion of broiler carcass in acetic acid and citric acid solution were significantly (P &lt;0.05) decrease the number of E. coli. There were interaction between immersion of broiler carcass in organic acids and observation time which significantly decrease the number of E. coli (p &lt;0.05). In conclusion, the immersion of carcass chicken in 3 % acetic acid, 3% citric acid, and their combination reduce the amount of E. coli. Key words: chicken carcass , citric acid 3%, acetic acid 3% , Escherichia coli

Linuron effects on microbiological characteristics of sandy soils as determined in a pot study

The aim of this study was to find what dosages of linuron introduced into soil can be tolerated by microorganisms, and whether a dosage equal to 100-times higher than the predicted environmental concentration (PEC) is harmful. A pot study was performed to determine the effects of the herbicide at PEC (4 mg kg−1), 5 times PEC (20 mg kg−1), and 100 times PEC (400 mg kg−1) on substrate-induced respiration (SIR), four enzyme activities (dehydrogenase, acid and alkaline phosphatases, and urease), ammonification and nitrification rates, plate counts of total bacteria, fungi, N2-fixing bacteria, nitrifiers and denitrifiers, and distribution of r- and K-strategists in sandy soils of different texture throughout 28 days of incubation. Linuron increased SIR and ammonification, especially at 100 times PEC. In contrast, a decrease in nitrate concentrations was detected in both soils treated with the highest dosage of linuron. Although some changes in microbial numbers were ascertained, they were transient (i.e. total bacteria, N2-fixing bacteria and nitrifiers) or not significant (i.e. total fungi and denitrifiers). Among the enzymes tested, dehydrogenase was the most sensitive to linuron, showing decreased activity for all treatments and two higher dosages in the loamy sand (LS) and sandy loam (SL) soils, respectively. The addition of 100 times PEC of linuron to LS resulted in the domination of slow-growing K-strategists on days 1 and 14. However, r-strategists dominated on both days 1 and 28 in SL. Our results indicate that linuron may disturb indigenous soil microorganisms, especially when released at high concentrations.

Microbiological Quality of Finfish and Shellfish with Special Reference to Shiga Toxin‐Producing Escherichia coli O157

The objective of this study was to determine the microbiological quality of fish and shellfish from Kolkata, India, with special emphasis on E. coli O157. Fresh and ice-preserved Labeo rohita, Catla catla, Cirrhinus mrigala, Oreochromis mossambica, Heteropneustesfossilis, Clarias batrachus, and Penaeus monodon were examined for total heterotrophic bacteria and coliform loads and presence of E. coli and E. coli serotype O157 by culture method. While the total plate count of bacteria was within acceptable or marginally acceptable limits for most samples, fishes were contaminated with coliforms, including E. coli, indicating poor hygiene and sanitary conditions. Although E. coli O157 could not be detected, a few samples were contaminated with non-O157 serotypes of enterohaemolysin- and Shiga toxin-producing E. coli, raising public health concern.

Comparison of rice straw and bamboo stick substrates in periphyton-based carp polyculture systems

An experiment was conducted to compare rice straw mat and kanchi (bamboo sticks) as substrates in periphyton-based polyculture systems. The experiment had three treatments: (a) no substrate (control), (b) rice straw as a substrate (3 � 2.7 kg pond � 1 ) and (c) kanchi as a substrate (390 kanchi pond � 1 ). Fingerlings (n 5 40) of rohu, Labeo rohita (24.5 � 0.5 g); mrigal, Cirrhinus mrigala (25.1 � 0.6 g); catla, Catla catla (25.8 � 0.5 g); common carp, Cyprinus carpio (27.6 � 0.6 g), and silver carp, Hypophthalmichthys molitrix (30.4 � 0.9 g) were stocked at a 3:2:2:2:1 ratio and cultured for 90 days. There were no diierences in the number of plankton, periphyton and macro-zoobenthos among the treatments. The total plate count of bacteria was higher in the rice straw treatment (41320 million cfu m � 2 ) than that in the kanchi treatment (11780 million cfu m � 2 ). Growth and the ¢nal mean weight of rohu, catla and common carp were higher in the substrate treatments than those in the control. Rice straw and kanchi treatment, respectively, resulted in 38% and 47% higher combined total weight gain over control. Gross margin analysis showed that rice straw treatment resulted in more pro¢t than the control and kanchi treatment. Therefore, rice straw has the potential to be used to increase production in the low-input rural aquaculture.

Genetic and phenotypic microdiversity of Ochrobactrum spp.

The diversity of Ochrobactrum anthropi, Ochrobactrum intermedium, Ochrobactrum tritici and Ochrobactrum grignonense in agricultural soil and on the wheat rhizoplane was investigated. O. anthropi was isolated both from soil and from the rhizoplane, O. intermedium and grignonense only from bulk soil, and O. tritici only from the wheat rhizoplane. On the genetic level, the immunotrapped isolates and a number of strains from culture collection mainly of clinical origin were compared with rep-PCR profiling using BOX primers, and a subset of these isolates and strains using REP primers. The isolates clustered according to their species affiliation. There was no correlation between rep clusters of O. anthropi isolates and habitat (place of isolation). The genetic diversity of Ochrobactrum at the species level as well as microdiversity of O. anthropi (number of BOX groups) was higher in soil than on the rhizoplane. Similarity values from genetic rep-PCR profiles correlated positively with DNA-DNA reassociation percentages. Isolates with >80.7% similarity in BOX profile and >86.4% in rep profile clustered within the same species. Similarity analysis of rep-PCR profiles is hence an alternative to DNA-DNA hybridization as a genomic criterion for species delineation within the genus Ochrobactrum. We used the substrate utilization system BIOLOG-GN to compare the immunotrapped isolates on the phenetic level. For the isolates from bulk soil, substrate utilization versatility (number of utilized substrates) and substrate utilization capacity (mean conversion rate of substrates) were slightly but significantly higher than for the isolates from the rhizoplane. This trend was also seen using API 20E and 20NE systems. Plate counts of total bacteria and the number of immunotrapped Ochrobactrum isolates per gram dry weight were higher for the rhizoplane than for the soil samples. The results of genetic and phenotypic analyses indicated a 'rhizosphere effect'; the diversity and metabolic capacity of Ochrobactrum isolates were higher in bulk soil, and the population density was higher on the wheat rhizoplane.

Effects of a biodegradable substrate, sugarcane bagasse and supplemental feed on growth and production of fringe-lipped peninsula carp, Labeo fimbriatus (Bloch)

Substrate-based farming practices are considered viable low-cost technologies as they help in sustainable aquaculture production. This investigation of 90-day duration was carried out in mud-bottomed cement tanks to study the effect of substrate and/or feed on growth and production of fringe-lipped peninsula carp, Labeo fimbriatus. The treatments consisted of sugarcane bagasse (T1), sugarcane bagasse plus fish-meal based diet (T2), and fish-meal based diet (T3). The substrate addition affected water quality; it decreased total ammonia. Dissolved oxygen was low following manuring and introduction of the substrate, but improved subsequently. Total plate count of bacteria in water was higher in bagassebased tanks; its value on bagasse was higher in T2 treatment than in T1. Fish growth and survival was the best in T2, followed by T3 and T1 treatments. Carcass proximate composition improved in all the treatments on termination of the experiment. The results indicate that L. fimbriatus effectively utilizes biofilm grown on sugarcane bagasse and provision of substrate reduces the need for artificial feed.

Analysis of bacterial community structure in sulfurous-oil-containing soils and detection of species carrying dibenzothiophene desulfurization (dsz) genes.

The selective effects of sulfur-containing hydrocarbons, with respect to changes in bacterial community structure and selection of desulfurizing organisms and genes, were studied in soil. Samples taken from a polluted field soil (A) along a concentration gradient of sulfurous oil and from soil microcosms treated with dibenzothiophene (DBT)-containing petroleum (FSL soil) were analyzed. Analyses included plate counts of total bacteria and of DBT utilizers, molecular community profiling via soil DNA-based PCR-denaturing gradient gel electrophoresis (PCR-DGGE), and detection of genes that encode enzymes involved in the desulfurization of hydrocarbons, i.e., dszA, dszB, and dszC. Data obtained from the A soil showed no discriminating effects of oil levels on the culturable bacterial numbers on either medium used. Generally, counts of DBT degraders were 10- to 100-fold lower than the total culturable counts. However, PCR-DGGE showed that the numbers of bands detected in the molecular community profiles decreased with increasing oil content of the soil. Analysis of the sequences of three prominent bands of the profiles generated with the highly polluted soil samples suggested that the underlying organisms were related to Actinomyces sp., Arthrobacter sp., and a bacterium of uncertain affiliation. dszA, dszB, and dszC genes were present in all A soil samples, whereas a range of unpolluted soils gave negative results in this analysis. Results from the study of FSL soil revealed minor effects of the petroleum-DBT treatment on culturable bacterial numbers and clear effects on the DBT-utilizing communities. The molecular community profiles were largely stable over time in the untreated soil, whereas they showed a progressive change over time following treatment with DBT-containing petroleum. Direct PCR assessment revealed the presence of dszB-related signals in the untreated FSL soil and the apparent selection of dszA- and dszC-related sequences by the petroleum-DBT treatment. PCR-DGGE applied to sequential enrichment cultures in DBT-containing sulfur-free basal salts medium prepared from the A and treated FSL soils revealed the selection of up to 10 distinct bands. Sequencing a subset of these bands provided evidence for the presence of organisms related to Pseudomonas putida, a Pseudomonas sp., Stenotrophomonas maltophilia, and Rhodococcus erythropolis. Several of 52 colonies obtained from the A and FSL soils on agar plates with DBT as the sole sulfur source produced bands that matched the migration of bands selected in the enrichment cultures. Evidence for the presence of dszB in 12 strains was obtained, whereas dszA and dszC genes were found in only 7 and 6 strains, respectively. Most of the strains carrying dszA or dszC were classified as R. erythropolis related, and all revealed the capacity to desulfurize DBT. A comparison of 37 dszA sequences, obtained via PCR from the A and FSL soils, from enrichments of these soils, and from isolates, revealed the great similarity of all sequences to the canonical (R. erythropolis strain IGTS8) dszA sequence and a large degree of internal conservation. The 37 sequences recovered were grouped in three clusters. One group, consisting of 30 sequences, was minimally 98% related to the IGTS8 sequence, a second group of 2 sequences was slightly different, and a third group of 5 sequences was 95% similar. The first two groups contained sequences obtained from both soil types and enrichment cultures (including isolates), but the last consisted of sequences obtained directly from the polluted A soil.