Total Bacterial Numbers Research Articles

Effects of rumen-protected glucose on ileal microbiota and genes involved in ileal epithelial metabolism and immune homeostasis in transition dairy cows

Optimizing diet formula with the aim of alleviating negative energy balance (NEB) is of great significance to the production performance of transition dairy cows. The objective of the study was to evaluate the effects of rumen-protected glucose (RPG) supplementation on ileal microbiota, the expression of genes involved in epithelial metabolism and immune homeostasis in the ileum of transition dairy cows. Ten Holstein dairy cows (age, 4.7 ± 0.5 years; bodyweight, 515 ± 42 kg; parity, 2.8 ± 0.4; body condition score, 3.2 ± 0.3; milk yield, 16.1 ± 3.7 kg/d) were randomly divided into two groups. The treatments were a basal diet plus 200 g/d of RPG (450 g/kg of glucose, 450 g/kg of coating fat and 100 g/kg of water) or a basal diet plus 90 g/d of coating fat (CON). Cows were provided with the diets for 21 days (from 1 week prepartum to 2 weeks postpartum) and euthanized on d 22 for taking samples. The ileal digesta samples were taken from the mid-ileum to analyze volatile fatty acid concentration and composition of digesta-associated microbiota. The ileal mucosa samples were taken from the mid-ileum for analysis of gene expression and composition of mucosa-associated microbiota. Ileal total volatile fatty acid concentration was lower (P = 0.018) in the PRG-supplemented group than in the CON group. Compared with CON group, the PRG supplementation up-regulated or tended to up-regulate (P < 0.10) the expression of PC, SGLT3, IGFBP5, PPARA, IL10, Occludin, and TPJ1, but down-regulated the expression of IL17A (P = 0.032) and tended to down-regulate (P < 0.10) the expression of TLR4, TLR9 and IL26. However, no differences (P > 0.10) were observed between the RPG and CON groups in both ileal total bacterial copy number and ileal bacterial beta diversity. Collectively, dietary RPG supplementation promoted epithelial metabolism and improved immune homeostasis in the ileum, with no influence on both digesta- and mucosa-associated ileal microbiota of transition dairy cows.

Water Quality Characteristics and Distribution of Bacterial Communities During Thermal Stratification in the Miyun Reservoir

As an important urban drinking water source, reservoirs are a special type of water body formed by artificial dams. Water quality of reservoirs directly affects the residents' drinking water safety. In order to reveal the characteristics of stratification and vertical changes of bacterial communities in the Miyun Reservoir, a drinking water source of Beijing, vertical stratified samples were collected during the stable stratified period of the reservoir (autumn). The vertical distribution characteristics of bacterial communities in the Miyun Reservoir were studied by using 16S rDNA terminal restriction fragment length polymorphism (T-RFLP) and quantitative PCR. Cluster analysis and multivariate statistical analysis were used to reveal the response relationships between bacterial communities and environmental factors. The results were as follows. ①The thermocline of the Miyun Reservoir was located at a water depth of 20-30 m, and the water temperature range was 15-19℃. The cluster analysis data of the seven sampled water layers were divided into an aerobic area (upper layer) and anoxic area (lower layer). The temperature, dissolved oxygen, and pH gradually decreased below 15 m. The electrical conductivity, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, and total nitrogen changed significantly after 15 m. The water quality showed obvious features in the vertical direction. ② The redundancy analysis (RDA) results showed that there were obvious vertical changes in the dissolved oxygen, pH, electrical conductivity, ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen between the aerobic and anoxic water layer. Those factors were the main environmental factors affecting the vertical distribution of the bacterial communities in the Miyun Reservoir. ③ The total bacterial number fluctuated with changes in the water depth. The Shannon-Wiener index and the number of T-RFs of bacteria in the aerobic zone were significantly higher than those in the anoxic zone, which indicates that there was significant stratification in the distribution of bacterial communities in the water of the Miyun Reservoir in autumn. This study explored the effects of water stratification on reservoir water quality and bacterial communities, and the findings provide a scientific basis for predicting water quality changes and reservoir management.

A flow cytometry method for bacterial quantification and biomass estimates in activated sludge

Absolute bacterial quantification receives little serious attention in the literature compared to sequencing, conceivably because it is considered unimportant and facile, or because existing methods are tedious, laborious and/or biased in nature. This is particularly true in engineered systems, including activated sludge, where such information underpins their design and operation. To overcome these limitations we built upon existing work and optimised and comprehensively validated, through comparison with epifluorescence microscopy (EFM), a rapid and precise flow cytometric protocol to enumerate total bacterial numbers in activated sludge. Insights into potential biases were evaluated using appropriate statistical analyses on this comparison, which spanned four orders of magnitude, as well as comparing volatile suspended solid (VSS) concentrations. The results suggest flow cytometry (FCM) is a rapid, reproducible and economical technique for quantifying total bacterial numbers and biomass concentrations in activated sludge, despite within order of magnitude discrepancies with EFM counts, which had inherent and evidently greater errors and biases than FCM. The use of FCM for routine monitoring over both EFM and VSS should help further understanding of the microbial ecology in, and the operation of, engineered systems.

Rapid Quantification of the Total Viable Bacterial Population on Human Hands Using Flow Cytometry with SYBR® Green I.

Monitoring the efficiency of hand washing typically relies on determining the presence or absence of targeted organisms on the hands, not necessarily determining if the method is working. The results focus on the organism studied and do not give a true reflection of the efficiency of the hygiene intervention. To obtain a better picture, this study tested flow cytometry with SYBR® Green I to quantify bacterial populations on the hands of participants in a healthcare training clinic at a University in South Africa. Participants "washed" both hands in a buffer solution in a sterile bag, and the total and viable bacterial populations numbers were determined using flow cytometry and compared with standard culture-based methods, testing for total coliforms, E. coli and heterotrophic organisms (IDEXX Colilert®-18 Quanti-Trays™ and SimPlates®) and fastidious organisms with hemolytic activity (Blood Agar). Compared to the culture-based method, flow cytometry rapidly distinguished total, viable, and dead bacterial populations in all samples. As expected, the culture-based methods gave lower bacterial counts and were limited by the detection limit of each test, requiring further testing with additional costs. Although the exact bacterial species in the population could not be identified with flow cytometry, viable counts from flow cytometric analysis were two times more precise than the data obtained with any of the culture-based methods tested. Flow cytometry was found to be suitable for immediate, accurate, and automatic detection of bacteria, and because it describes the viable bacterial population, it is ideal to monitor hand hygiene interventions. © 2019 International Clinical Cytometry Society.

Дослідження загального мікробного числа та кількості мікроміцетів у пташнику за застосування пробіотичного препарату

Дослідження загального мікробного числа та кількості мікроміцетів у пташнику за застосування пробіотичного препарату

The impact of E-beam treatment on the microbial population and sensory quality of hard annatto-coloured cheese

The effects of E-beam radiation on microbiota, colour, texture and sensorial properties of hard annatto-coloured cheese during storage at 4 and 14 °C were studied. Doses of up to 2 kGy provoked a decrease in the total bacterial number, although microbiota recovery to initial levels during storage, even under refrigeration temperature, was observed. However, a higher temperature (14 °C) was required to detect bacterial growth in cheese treated at 3 kGy. Moreover, the effects of the dose on the hardness, springiness, cohesiveness and colour parameters were interdependent of the storage conditions. According to the combined effects of E-beam treatment and storage conditions, multivariate cluster analysis allowed treated cheeses irradiated at 0–1 kGy (cluster 1) to be distinguished from those irradiated at 2–3 kGy (cluster 2), which were stored at 4 °C for 28 days. Cluster 3 included irradiated cheeses (1–3 kGy) stored at a higher temperature (14 °C). Although off-odour and off-flavours arose immediately after treatment, they disappeared progressively during storage at doses lower than 2 kGy. Nevertheless, consumers could detect changes in the colour derived from the radiation at 2 kGy, however, those changes may be unimportant because of the wide colour ranges of commercial annatto-coloured cheeses.

Performance and Bacterial Communities for Bio-drying with Thermophili Bacteria of Sewage Sludge

This study was conducted to evaluate the effect of the sewage sludge treatment method using bio-drying with Ultra-Thermophilic Aerobic Microorganisms (UTAMs). Twelve specific odorous compounds and various sources of bacteria were tested using the sewage sludge treatment method. Sewage sludge was mixed with a seed material and was composted for 47 days. During composting, the temperature was maintained at 80-90oC. The concentrations of the 12 specific odorous compounds after composting did not exceed the allowable exhaust standard for odor. In terms of the bacterial community number after composting, the thermophile bacterial number was 60% of the total bacterial number. The thermophile bacterial ratio after composting increased by 23% compared to the initial composting. The 16S rRNA gene demonstrated that the change in the bacterial community structure was coupled with shifts in the bio-drying process. Therefore, both stable composting operation and economic benefit can be expected when an ultra-thermophilic composting process is applied to sewage sludge.

A Small GTPase, RhoA, Inhibits Bacterial Infection Through Integrin Mediated Phagocytosis in Invertebrates.

The Ras GTPase superfamily, including more than 100 members, plays a vital role in a number of cellular processes, such as cytoskeleton recombination, gene expression, and signaling pathway regulation. Some members of the superfamily participate in innate immunity in animals. However, there have been few studies of RhoA on this aspect. In the present study, we identified a RhoA GTPase in the shrimp Marsupenaeus japonicus and named it MjRhoA. Expression of MjRhoA was significantly upregulated in hemocytes and heart of shrimp challenged with Vibrio anguillarum. Overexpression of MjRhoA in shrimp caused the total bacterial number to decrease significantly and knockdown of MjRhoA increased the bacterial number obviously, with a consequent decline in shrimp survival. These results confirmed the antibacterial function of MjRhoA in shrimp. Further study showed that rate of phagocytosis of hemocytes was decreased in MjRhoA-knockdown shrimp. Interestingly, we observed that MjRhoA was translocated onto the hemocyte membrane at 1 h post V. anguillarum challenge. The expression levels of the β-integrin-mediated phagocytosis markers ROCK2 and Arp2/3 declined significantly after knockdown of MjRhoA. These results suggested that the antibacterial function of MjRhoA was related to β-integrin-mediated phagocytosis in shrimp. Our previous study identified that a C-type lectin, hFcLec4, initiated β-integrin mediated phagocytosis after bacterial infection. Thus, knockdown of hFcLec4 and β-integrin was performed. The results showed that the translocation of MjRhoA from the cytoplasm to membrane was inhibited and the expression level of MjRhoA was decreased, suggesting that MjRhoA participated in hFcLec4-integrin mediated phagocytosis. Therefore, our study identified a new hFcLec4-integrin-RhoA dependent phagocytosis against bacterial infection in shrimp.

Potential of Fructooligosaccharides and Xylooligosaccharides as Substrates To Counteract the Undesirable Effects of Several Antibiotics on Elder Fecal Microbiota: A First in Vitro Approach.

Fructooligosaccharides (FOS) and xylooligosaccharides (XOS) were employed as substrates for in vitro fermentations to assess their capacity to counteract the effects caused by three antibiotics (ABs) at different doses on the elderly gut microbiota and its metabolic activity. The AB type and dose scarcely affected the total bacterial numbers and the microbiota composition after 24 h. However, in the presence of ABs, the relative percentages of Lactobacillus decreased (from 11.4% to 3.2% in the presence of XOS1), as well as the butyrate production, whereas the population of Bacteroides increased significantly in the presence of XOS1 (from 27.5% to 55.7%). FOS were able to counteract these effects by increasing the butyrate production and the number of Lactobacillus, while maintaining the number of Bacteroides almost constant and decreasing the clostridia. XOS2 (mainly DP = 2-4) also showed ability to increase the percentages of Bifidobacterium and the production of both butyrate and acetate.

Dalangtan Playa (Qaidam Basin, NW China): Its microbial life and physicochemical characteristics and their astrobiological implications.

Dalangtan Playa is the second largest salt playa in the Qaidam Basin, north-western China. The hyper saline deposition, extremely arid climate and high UV radiation make Dalangtan a Mars analogue both for geomorphology and life preservation. To better understand microbial life at Dalangtan, both culture-dependent and culture-independent methods were examined and simultaneously, environment conditions and the evaporitic mineral assemblages were investigated. Ten and thirteen subsurface samples were collected along a 595-cm deep profile (P1) and a 685-cm deep profile (P2) respectively, and seven samples were gathered from surface sediments. These samples are composed of salt minerals, minor silicate mineral fragments and clays. The total bacterial cell numbers are (1.54±0.49) ×105 g−1 for P1 and (3.22±0.95) ×105 g−1 for P2 as indicated by the CAtalyzed Reporter Deposition- Fluorescent in situ Hybridization (CARD-FISH). 76.6% and 75.7% of the bacteria belong to Firmicutes phylum respectively from P1 and P2. In total, 47 bacteria and 6 fungi were isolated from 22 subsurface samples. In contrast, only 3 bacteria and 1 fungus were isolated from 3 surface samples. The isolated bacteria show high homology (≥97%) with members of the Firmicutes phylum (47 strains, 8 genera) and the Actinobacteria phylum (3 strains, 2 genera), which agrees with the result of CARD-FISH. Isolated fungi showed ≥98% ITS1 homology with members of the phylum Ascomycota. Moisture content and TOC values may control the sediments colonization. Given the deliquescence of salts, evaporites may provide refuge for microbial life, which merits further investigation. Halotolerant and spore-forming microorganisms are the dominant microbial groups capable of surviving under extreme conditions. Our results offer brand-new information on microbial biomass in Dalangtan Playa and shed light on understanding the potential microbial life in the dried playa or paleo-lakes on Mars.

Dietary values of macroalgae Porphyra haitanensis in Litopenaeus vannamei under normal rearing and WSSV challenge conditions: Effect on growth, immune response and intestinal microbiota

Two trials were conducted to determine the effects of dietary macroalgae Porphyra haitanensis on growth, immunity and intestinal microbiota of Litopenaeus vannamei. In trial 1, shrimp (mean initial wet weight about 0.64 g) were fed with seven diets (P0, P1, P2, P3, P4, P5 and P6) containing 0% (basal diet), 1%, 2%, 3%, 4%, 5% and 6% P. haitanensis in triplicate for 60 days. Growth performance (weight gain, WG; specific growth rate, SGR) of shrimp fed the P4 diet were significantly higher than that of shrimp fed P0, P5 and P6 diets (P < 0.05) but without significant differences with shrimp fed P1-P3 diets (P > 0.05). Hepatopancreas phenoloxidase (PO) activity of shrimp fed the P. haitanensis containing diets was significantly higher than that of shrimp fed the basal diet (P0) (P < 0.05). Total haemocyte count (THC) of shrimp fed basal diet (P0) was significantly lower than that of shrimp fed diets containing P. haitanensis. Our results declared that dietary P. haitanensis supplementation increases the abundance of beneficial bacterials such as Nitrosopumilus, Marinobacter or Bifidobacterium and reduces the abundance of harmful bacterias such as Vibrio, and especially pronounced in P4 diet treatment. In trial 2, a WSSV injection challenge test was conducted for 7-day after the rearing trial and shrimp survival was also compared among treatments. A sudden shrimp death was found from the 4th day, and values of survival of shrimp fed the P3-P4 diets were higher than that of shrimp fed other diets during 4–7 days challenge test. The immune response in trial 2 were characterized by higher superoxide dismutase activity (SOD) and PO activities, lower THC and higher HCT compared to levels found in trial 1. In conclusion, suitable dietary P. haitanensis could enhance the growth performance, antioxidant capacity and alter total bacterial numbers or microbial diversity of L. vannamei and furthermore reduce oxidative stress and immune depression challenged by WSSV injection stress, and the level of P. haitanensis supplemented in the diet should be between 2.51% and 3.14%.

Estimation of lactic acid bacterial cell number by DNA quantification.

Lactic acid bacteria are provided by fermented foods, beverages, medicines, and supplements. Because the beneficial effects of medicines and supplements containing functional lactic acid bacteria are related to the bacterial cell number, it is important to establish a simple method for estimating the total number of lactic acid bacterial cells in the products for quality control. Almost all of the lactic acid bacteria in the products are dead, however, making it difficult to estimate the total number of lactic acid bacterial cells in the products using a standard colony-counting method. Here we estimated the total lactic acid bacterial cell number in samples containing dead bacteria by quantifying the DNA. The number of viable Enterococcus faecalis 0831-07 cells decreased to less than 1 × 10-8 by 15 min of heat treatment at 80°C. The amount of extracted DNA from heat-treated cells was 78% that of non-heated cells. The number of viable Lactobacillus paraplantarum 11-1 cells decreased to 1 × 10-4 after 4 days culture. The amount of extracted DNA of the long-cultured cells, however, was maintained at 97%. These results suggest that cell number of lactic acid bacteria killed by heat-treatment or long-term culture can be estimated by DNA quantification.

Identification of Dysbiosis Related Bacteria from New Zealand’s White Rabbit Intestinal Treated With Lactobacillus plantarum IS-10506 as Probiotics Food Supplementation

The gastrointestinal microoganisms encompass thousands of bacterial species that constitute a relatively stable ecosystem inside human body. Dysbiosis is an imbalance condition of beneficiary microbacteria cause by newer microorganism. This research aimed to investigate the effect of L. plantarum IS-10506 as probiotics supplementation on total bacterial and Enterobacteriaceae count; and also to identify the dysbiosis causing bacteria. Total bacterial and Enterobacteriaceae number on both control and test group were determined by Total Plate Count method. Identification of dysbiosis related bacteria were determined by fermentation test, gram staining, and Microbact™ 12A kit. The TPC result of total bacterial population on control group was 222.67 x 106 cfu/ml, while the probiotics induced group was 210.33 x 106 cfu/ml. As for the TPC result for Enterobacteriaceae population from control group was 12.00 x 106 cfu/ml, Enterobacteriaceae population in the probiotics induced group was 11.66 x 106 cfu/ml. Four genera related to dysbiosis has been isolated from the intestinal sample and all are rod-shaped Gram negative bacteria. In conclusion, the use of L. plantarum IS-10506 as food supplementation has reduced the total bacterial count. Four genera of dysbiosis related bacteria has been identified from the intestinal sample which include Eschericia, Serratia, Enterobacter, and Citrobacter.

Ugly ducklings\u2014the dark side of plastic materials in contact with potable water

Bath toys pose an interesting link between flexible plastic materials, potable water, external microbial and nutrient contamination, and potentially vulnerable end-users. Here, we characterized biofilm communities inside 19 bath toys used under real conditions. In addition, some determinants for biofilm formation were assessed, using six identical bath toys under controlled conditions with either clean water prior to bathing or dirty water after bathing. All examined bath toys revealed notable biofilms on their inner surface, with average total bacterial numbers of 5.5 × 106 cells/cm2 (clean water controls), 9.5 × 106 cells/cm2 (real bath toys), and 7.3 × 107 cells/cm2 (dirty water controls). Bacterial community compositions were diverse, showing many rare taxa in real bath toys and rather distinct communities in control bath toys, with a noticeable difference between clean and dirty water control biofilms. Fungi were identified in 58% of all real bath toys and in all dirty water control toys. Based on the comparison of clean water and dirty water control bath toys, we argue that bath toy biofilms are influenced by (1) the organic carbon leaching from the flexible plastic material, (2) the chemical and biological tap water quality, (3) additional nutrients from care products and human body fluids in the bath water, as well as, (4) additional bacteria from dirt and/or the end-users’ microbiome. The present study gives a detailed characterization of bath toy biofilms and a better understanding of determinants for biofilm formation and development in systems comprising plastic materials in contact with potable water.

PENGARUH LAMA PENYIMPANAN DAGING AYAM PADA SUHU RUANG DAN REFRIGERATOR TERHADAP ANGKA LEMPENG TOTAL BAKTERI DAN ADANYA BAKTERI Salmonella sp

The purpose of this research is to understand the existence of bacteria contamination as an indicator of consumption feasibility in chicken meat. The research used 100 grams of chicken meat sample from on of the traditional market in Medan. Each sample was grown on Nutrient Agar and Salmonella Shigella Agar media. If the colony grows on SSA media that appear convex and clear yellow, it will followed by biochemical tests including Triple Sugar Iron Agar and Simmons Citrate Agar. The results showed that chicken meat storage at room temperature for 9 hours and 12 hours above maximum value of SNI (above 1 x 106), that is 173 x 104 and 354 x 104. The results of analysis of variance samples of chicken meat stored at room temperature showed the value of Fcount (101,356) &gt; Ftable (2,866), storage duration of chicken meat at the room temperature have a significant effect to the total plate bacteria count. The results of analysis of variance samples of chicken meat stored at refrigerator temperature showed the value of Fcount (21,443) &gt; Ftable (2,866), storage duration of chicken meat at the refrigerator temperature have a significant effect to the total plate bacteria count. Based on the results of further tests using BNT test obtained that the storage duration of chicken meat at room temperature for 3 hours have a very significant effect on the total plate bacteria count. The results of further tests using BNT test, that chicken meat storage at room temperature have a very significant effect between treatment for 0 hours and 3 hours of storage to total plate bacteria count. While at refrigerator temperature have a very significant effect between treatment for 9 hours and 12 hours of storage to total bacterial plate number. The results showed that 2 samples from 10 samples tested were positive contaminated by Salmonella sp. This indicates that the quality of chicken meat that has been stored for more than 9 hours at room temperature does not accord suit to the standards based on Indonesian Nasional Standard. Keywords: Chicken Meat, Storage Duration, Total Plate Bacteria Count, Salmonella sp.

Streptococcus oralis maintains homeostasis in oral biofilms by antagonizing the cariogenic pathogen Streptococcus mutans.

Bacteria residing in oral biofilms live in a state of dynamic equilibrium with one another. The intricate synergistic or antagonistic interactions between them are crucial for determining this balance. Using the six-species Zürich "supragingival" biofilm model, this study aimed to investigate interactions regarding growth and localization of the constituent species. As control, an inoculum containing all six strains was used, whereas in each of the further five inocula one of the bacterial species was alternately absent, and in the last, both streptococci were absent. Biofilms were grown anaerobically on hydroxyapatite disks, and after 64h they were harvested and quantified by culture analyses. For visualization, fluorescence in situ hybridization and confocal laser scanning microscopy were used. Compared with the control, no statistically significant difference of total colony-forming units was observed in the absence of any of the biofilm species, except for Fusobacterium nucleatum, whose absence caused a significant decrease in total bacterial numbers. Absence of Streptococcus oralis resulted in a significant decrease in Actinomyces oris, and increase in Streptococcus mutans (P<.001). Absence of A.oris, Veillonella dispar or S.mutans did not cause any changes. The structure of the biofilm with regards to the localization of the species did not result in observable changes. In summary, the most striking observation of the present study was that absence of S.oralis resulted in limited growth of commensal A.oris and overgrowth of S.mutans. These data establish highlight S.oralis as commensal keeper of homeostasis in the biofilm by antagonizing S.mutans, so preventing a caries-favoring dysbiotic state.

Long-term use of cover crops and no-till shift soil microbial community life strategies in agricultural soil.

Reducing tillage and growing cover crops, widely recommended practices for boosting soil health, have major impacts on soil communities. Surprisingly little is known about their impacts on soil microbial functional diversity, and especially so in irrigated Mediterranean ecosystems. In long-term experimental plots at the West Side Research and Extension Center in California’s Central Valley, we characterized soil microbial communities in the presence or absence of physical disturbance due to tillage, in the presence or absence of cover crops, and at three depths: 0–5, 5–15 and 15–30 cm. This characterization included qPCR for bacterial and archaeal abundances, DNA sequencing of the 16S rRNA gene, and phylogenetic estimation of two ecologically important microbial traits (rRNA gene copy number and genome size). Total (bacterial + archaeal) diversity was higher in no-till than standard till; diversity increased with depth in no-till but decreased with depth in standard till. Total bacterial numbers were higher in cover cropped plots at all depths, while no-till treatments showed higher numbers in 0–5 cm but lower numbers at lower depths compared to standard tillage. Trait estimates suggested that different farming practices and depths favored distinctly different microbial life strategies. Tillage in the absence of cover crops shifted microbial communities towards fast growing competitors, while no-till shifted them toward slow growing stress tolerators. Across all treatment combinations, increasing depth resulted in a shift towards stress tolerators. Cover crops shifted the communities towards ruderals–organisms with wider metabolic capacities and moderate rates of growth. Overall, our results are consistent with decreasing nutrient availability with soil depth and under no-till treatments, bursts of nutrient availability and niche homogenization under standard tillage, and increases in C supply and variety provided by cover crops. Understanding how agricultural practices shift microbial abundance, diversity and life strategies, such as presented here, can assist with designing farming systems that can support high yields, while enhancing C sequestration and increasing resilience to climate change.

Comparative analyses of microbial structures and gene copy numbers in the anaerobic digestion of various types of sewage sludge

Anaerobic co-digestion of various sewage sludges is a promising approach for greater recovery of energy, but the process is more complicated than mono-digestion of sewage sludge. The applicability of microbial structure analyses and gene quantification to understand microbial conditions was evaluated. The results show that information from gene analyses is useful in managing anaerobic co-digestion and damaged microbes in addition to conventional parameters like total solids, pH and biogas production. Total bacterial 16S rRNA gene copy numbers are the most useful tools for evaluating unstable anaerobic digestion of sewage sludge, rather than mcrA and total archaeal 16S rRNA gene copy numbers, and high-throughput sequencing. First order decay rates of gene copy numbers during pH failure were higher than typical decay rates of microbes in stable operation. The sequencing analyses, including multidimensional scaling, showed very different microbial structure shifts, but the results were not consistent.

Plant Materials are Sustainable Substrates Supporting New Technologies of Plant-Only-Based Culture Media for in vitro Culturing of the Plant Microbiota.

In order to improve the culturability and biomass production of rhizobacteria, we previously introduced plant-only-based culture media. We herein attempted to widen the scope of plant materials suitable for the preparation of plant-only-based culture media. We chemically analyzed the refuse of turfgrass, cactus, and clover. They were sufficiently rich to support good in vitro growth by rhizobacteria isolates representing Proteobacteria and Firmicutes. They were also adequate and efficient to produce a cell biomass in liquid batch cultures. These culture media were as sufficient as artificial culture media for the cultivation and recovery of the in situ rhizobacteria of barley (Hordeum murinum L.). Based on culture-dependent (CFU plate counting) and culture-independent analyses (qPCR), mowed turfgrass, in particular, supported the highest culturable population of barley endophytes, representing >16% of the total bacterial number quantified with qPCR. This accurately reflected the endophytic community composition, in terms of diversity indices (S′, H′, and D′) based on PCR-DGGE, and clustered the plant culture media together with the qPCR root populations away from the artificial culture media. Despite the promiscuous nature of the plant materials tested to culture the plant microbiome, our results indicated that plant materials of a homologous nature to the tested host plant, at least at the family level, and/or of the same environment were more likely to be selected. Plant-only-based culture media require further refinements in order to provide selectivity for the in vitro growth of members of the plant microbiome, particularly difficult-to-culture bacteria. This will provide insights into their hidden roles in the environment and support future culturomic studies.

Inhibitory effect of self-generated extracellular dissolved organic carbon on carbon dioxide fixation in sulfur-oxidizing bacteria during a chemoautotrophic cultivation process and its elimination

The features of extracellular dissolved organic carbon (EDOC) generation in two typical aerobic sulfur-oxidizing bacteria (Thiobacillus thioparus DSM 505 and Halothiobacillus neapolitanus DSM 15147) and its impact on CO2 fixation during chemoautotrophic cultivation process were investigated. The results showed that EDOC accumulated in both strains during CO2 fixation process. Large molecular weight (MW) EDOC derived from cell lysis and decay was dominant during the entire process in DSM 505, whereas small MW EDOC accounted for a large proportion during initial and middle stages of DSM 15147 as its cytoskeleton synthesis rate did not keep up with CO2 assimilation rate. The self-generated EDOC feedback repressed cbb gene transcription and thus decreased total bacterial cell number and CO2 fixation yield in both strains, but DSM 505 was more sensitive to this inhibition effect. Moreover, the membrane bioreactor effectively decreased the EDOC/TOC ratio and improved carbon fixation yield of DSM 505.