Growth Rate Of Culture Research Articles

Minimum nitrogen cell quota for maximal growth rate in cycloturbidostat cultures of Picochlorum oklahomense

Replicate cycloturbidostats cultures of Picochlorum oklahomense were manipulated to quantify the minimum nitrogen cell quota supporting maximum growth rate and to study the effects of nitrogen limitation on cycloturbidostat cultures growing at near-μmax under steady-state, balanced growth conditions. Results show that cyclical diurnal neutral lipid accumulation and ultradian growth are not mutually exclusive, and that cycloturbidostat cultures may be maintained near or at the threshold of N-limitation to control cell composition and modulate biomass and lipid productivity. Using this novel approach, we have identified the threshold of N limitation in P. oklahomense and investigated the effects of N limitation on replicate cycloturbidostat cultures. Mildly N-limited cultures grew rapidly (87 % μmax) and maintained near optimal physiology, while also accumulating neutral lipids during the photoperiod. Flow cytometry revealed differences in temporal patterns between treatments, demonstrating the importance of the cell-based approach in manipulating microalgal cultures. This study highlights the utility of turbidostats in experimental phycology and defines a scantly explored concept in the study of N limitation, the threshold of N cell quota necessary to support μmax below which cells are forced to re-allocate resources and slow growth, denoted QN, T.

The impact of vegetables and durum wheat value chains to alleviate unemployment and migration in selected woredas of oromia regional state, ethiopia.

Poor countries, like Ethiopia, at this time are highly attached with different problems like poverty, unemployment, backward culture, famine, illiteracy, and high population growth rate. The study was to contribute creating evidence from the government and NGOs intervention experience for further supporting durum wheat and vegetable value chains players in strengthening, expanding and in creating jobs for vulnerable youth in the target areas. With the specific objectives of this research was identify elements of the intervention that shall be further promoted, adjusted or discontinued, identify a range of market-driven non-farm business and income generation opportunities for youth groups and cooperatives, within the durum wheat and vegetable value chains and across interconnecting markets and identify the COVID-19-related impact on youth and women in the target value chains. Sample size includes vegetable traders 123, for wheat trader 261 and for wheat and vegetable producers 384. Cross-tabulation, charts, figures, percentages, and graphs used along with narrative accounts to present the findings. Qualitative data collected via KII narrated and interpreted to supplement data obtained through questionnaire. Wheat processing private companies in the study areas has been creating job opportunities for a number of unemployed youths. The majority of the durum wheat producers 90 (35.86%) and 62 (35.06%) in the study areas were supplied their product to whole seller and local collectors. Both wheat and vegetable target producers were asked about the possible impact of the current pandemic Covid-19 on their farm production. Creating strong linkages among different actors and/ sectors in the value chain for developments of both durum wheat and vegetable value chain developments and through creating job for youth and stemming irregular migration is crucial recommended.

Utilization of phosphonic acid compounds by marine bacteria of the genera Phaeobacter, Ruegeria, and Thalassospira (α-Proteobacteria).

Phosphonic acid (phosphonate) that possesses a carbon-phosphours bond is a chemically stable form of organic phosphorus. Various phosphonic acids are widely distributed in oceanic waters; in particular, methylphosphonic acid (namely methylphosphonate) is believed to be responsible for global methane production. To discuss the microbial degradation of phosphonic acids, we investigated the utilization of phosphonic acid compounds by cultures of marine bacteria, Phaeobacter sp., Ruegeria sp. (Rhodobacterales), and Thalassospira sp. (Rhodospirillales). These bacterial cultures were able to grow on methylphosphonic acid as well as on the tested alkyl-, carboxy-, aminoalkyl-, and hydroxyalkyl-phosphonic acid compounds. Cell yields and growth rates of Ruegeria and Thalassospira cultures grown on methyl-, ethyl-, propyl-, and butyl-phosphonic acid compounds tended to decrease with increasing alkyl chain length. In contrast, Phaeobacter sp. grew well on such alkyl-phosphonic acids. Our results suggest that these marine bacteria, which exhibit varied utilization, are involved in microbial degradation of various phosphonic acid compounds.

Growth parameters and responses of green algae across a gradient of phototrophic, mixotrophic and heterotrophic conditions.

Many studies have shown that algal growth is enhanced by organic carbon and algal mixotrophy is relevant for physiology and commercial cultivation. Most studies have tested only a single organic carbon concentration and report different growth parameters which hampers comparisons and improvements to algal cultivation methodology. This study compared growth of green algae Chlorella vulgaris and Chlamydomonas reinhardtii across a gradient of photoautotrophic-mixotrophic-heterotrophic culture conditions, with five acetate concentrations. Culture growth rates and biomass achieved were compared using different methods of biomass estimation. Both species grew faster and produced the most biomass when supplied with moderate acetate concentrations (1–4 g L−1), but light was required to optimize growth rates, biomass yield, cell size and cell chlorophyll content. Higher acetate concentration (10 g L−1) inhibited algal production. The choice of growth parameter and method to estimate biomass (optical density (OD), chlorophyll a fluorescence, flow cytometry, cell counts) affected apparent responses to organic carbon, but use of OD at 600, 680 or 750 nm was consistent. There were apparent trade-offs among exponential growth rate, maximum biomass, and culture time spent in exponential phase. Different cell responses over 1–10 g L−1 acetate highlight profound physiological acclimation across a gradient of mixotrophy. In both species, cell size vs cell chlorophyll relationships were more constrained in photoautotrophic and heterotrophic cultures, but under mixotrophy, and outside exponential growth phase, these relationships were more variable. This study provides insights into algal physiological responses to mixotrophy but also has practical implications for choosing parameters for monitoring commercial algal cultivation.

Central Metabolism and Growth Rate Impacts on Hydrogen and Carbon Isotope Fractionation During Amino Acid Synthesis in E. coli.

Compound specific stable isotope analysis (CSIA) of amino acids from bacterial biomass is a newly emerging powerful tool for exploring central carbon metabolism pathways and fluxes. By comparing isotopic values and fractionations relative to water and growth substrate, the impact of variable flow path for metabolites through different central metabolic pathways, perturbations of these paths, and their resultant consequences on intracellular pools and resultant biomass may be elucidated. Here, we explore the effects that central carbon metabolism and growth rate can have on stable hydrogen (δ2H) and carbon (δ13C) compound specific isotopic values of amino acids, and whether diagnostic isotopic fingerprints are revealed by these paired analyses. We measured δ2H and δ13C in amino acids in the wild type Escherichia coli (MG1655) across a range of growth rates in chemostat cultures to address the unknown isotopic consequences as metabolic fluxes are shuffled between catabolic and anabolic metabolisms. Additionally, two E. coli knockout mutants, one with deficiency in glycolysis –pgi (LC1888) and another inhibiting the oxidative pentose phosphate pathway (OPPP) –zwf (LC1889), were grown on glucose and used as a comparison against the wild type E. coli (MG1655) to address the isotopic changes of amino acids produced in these perturbed metabolic pathways. Amino acid δ2H values, which collectively vary in composition by more than 400‰, are altered along with δ13C values demonstrating fundamental shifts in central metabolic pathways and/or fluxes. Within our linear discriminant analysis with a simple model organism to examine potential amino acid fingerprinting, our knockout strains and variable growth rate samples plot across a wider array of organism classification than merely within the boundaries of other bacterial data.

Assessment of Modified Trans-umbilical Port Placement in Laparoscopy.

Primary port placement is a critical step in any laparoscopic procedure. Although the safety and efficacy of open versus closed technique has been much debated, no particular technique is considered as the best. Therefore, over the period of time different methods have been developed and applied in order to perform laparoscopy procedures, Midat hospital has been using a version of modified trans-umbilical open technique for primary port entry from 2 decades and this study is being carried out to evaluate the technique. Retrospective review was conducted. The patients who underwent laparoscopy surgery by modified trans-umbilical port placement at Midat hospital from June 2019- April 2020 were included in this study. A total of 100 cases were studied. Cholelithiasis was the main indication of surgery. The mean time recorded to establish pneumoperitoneum was 3.4±1.3 minutes. The rate of umbilical swab culture growth was 1%, pre-peritoneal port placements was 2%. Post-operative primary port site infection rate was 4%. No intra-abdominal injury was noted during the entry of primary port and there was no port site hematoma or recorded hernia over the period of one year. This technique of modified trans-umbilical primary port placement is one of the safest, fastest and easiest techniques to enter the peritoneal cavity.

Low specific growth rate and temperature in fed-batch cultures of a beta-propeller phytase producing Pichia pastoris strain under GAP promoter trigger increased KAR2 and PSA1-1 gene expression yielding enhanced extracellular productivity

Previously, we showed that the methylotrophic yeast Pichia pastoris (syn. Komagataella phaffii) could produce and secrete the beta-propeller phytase FTEII in an active form under the control of the AOX1 promoter and methanol as the inductor. In this work, we engineered P. pastoris strains to construct a constitutive P. pastoris expression system (GAP promoter) and extracellularly produce the phytase FTEII. We optimized the culture conditions to increase the extracellular volumetric phytase productivity (Qp) and evaluated the impact of the optimization process on the physiological response of the host. Moreover, we analyzed the expression levels of the FTEII gene and endogenous genes for P. pastoris cells in cultures with the lowest and highest Qp to understand which processes (from heterologous gene expression to protein secretion) might be responsible for the increase in Qp. The results indicate that a low specific growth rate and temperature in the fed-batch phase increases the Qp, which was correlated with an upregulation of the KAR2 and PSA1–1/MPG1 genes rather than increased heterologous gene transcription.

Indoor culture scaling of Gracilaria chilensis (Florideophyceae, Rhodophyta): The effects of nutrients by means of different culture media

Gracilaria chilensis is distributed in New Zealand (including Chatham Island) and South America. This species has a three-stage sexual life cycle, as well as asexual and vegetative reproduction, and is commercially important as it is a valuable source for producing agar. However, basing the crops exclusively on clonal reproduction and vegetative propagation has led to a reduction in their genotypic diversity, an increase in their susceptibility to infection by epiphytes, and a decrease in their quality. Thus, it is important to establish indoor cultures of G. chilensis from thalli with a mixed reproductive regime (sexual and asexual) that maintains the genetic variability of the cultivars. In this study, the biomass, growth rate, and productivity of indoor cultures of G. chilensis were evaluated (as a first approach) using various culture media (i.e., von Stosch medium (VS), Basfoliar® Aktiv (BF), and mixtures of VS and BF, namely, VS/BF-A and VS/BF-B). The VS/BF-A medium showed the best results in terms of biomass (51.8 ± 3.7 g m–2), growth rate (4.55 ± 0.43 %d–1), and productivity (14 g m–2 d–1), including the occurrence of thalli with cystocarps. The positive results using the VS/BF-A medium could be attributed to the fact that BF provides different elements (K, Cu, Mo, and Zn) that are crucial, since they are involved in numerous physiological functions in the algae, and also to the N:P ratio utilized (1:1), which positively affects growth and productivity. This information provides pivotal updated knowledge regarding cultures of G. chilensis under controlled conditions, promoting its successful cultivation for productive purposes.

Human amniotic fluid as a source of stem cells.

Human amniotic fluid collected during amniocentesis contains a heterogeneous population of differentiated and undifferentiated cells. Properties and number of these cells vary depending on the gestational age and the presence of potential fetal pathologies. The aim of this study was to analyze the effects of maternal, fetal, and environmental factors on the success rates of amniotic fluid stem cell cultures, the number of human amniotic fluid stem cells (hAFSC), their growth rates in primary cultures, and the number of cell passages. The study included 355 patients qualified for genetic amniocentesis at the Prenatal Genetic Unit, Department of Obstetrics, Gynecology and Oncologic Gynecology, Nicolaus Copernicus University Medical College in Bydgoszcz in 2011–2017. The mean age of the study participants was 34 ± 6.2 years, and mean gravidity amounted to 2.48 ± 1.4. Amniotic fluid sample volume turned out to be a highly significant (p < 0.01) predictor of culture success, and the relationship was particularly evident in women older than 40 years. Another highly significant predictor of culture success was the presence of two cell populations in the sample (p < 0.01). The likelihood of culture success correlated significantly (p < 0.05) with the season of the year at the time of amniocentesis. The number of cell passages differed significantly depending on the maternal age (p < 0.01). The number of passages also showed a highly significant relationship with the season of the year the sample was obtained (p < 0.01). Younger maternal age was identified as a determinant of high passage number (≥3), and another highly significant determinant of high passage number was the presence of two cell populations in the amniotic fluid sample (p < 0.01). Percentage of successfully established hAFSC cultures and the number of passages depended on amniotic fluid volume, the presence of two cell populations within the sample, and the season of the year. Individual characteristics of the donors, such as age and gravidity, did not exert a significant effect on the number of isolated hAFSCs and the rate of their growth. Patients’ place of residence, fetal karyotype, transportation time, and purity of the samples did not affect the success rates for primary cultures and the number of passages.

Ocean acidification stimulation of phytoplankton growth depends on the extent of departure from the optimal growth temperature

Ocean acidification and warming are two major environmental stressors; however, the generality of how warming will alter growth responses of phytoplankton to ocean acidification is less known. Here, enhancement of growth by high CO2 (HC) in Phaeodactylum tricornutum and Thalassiosira weissflogii was most prominent at optimum temperature. The extent to which growth rates in HC cultures were raised compared to low CO2 (LC) cultures tended to decrease with increasing or decreasing temperature, compared to the optimum. Further mechanistic studies in P. tricornutum revealed that cellular carbon and nitrogen content, superoxide dismutase activity, and respiration were generally higher in HC than those in LC at high and low temperatures, whereas PSII photochemical parameters were generally lower in HC than in LC at high and low temperatures. These results indicate that HC-grown cells needed to invest more energy and materials to maintain intracellular homeostasis and repair damage induced by the unsuitable temperatures.

Microalgal mediated antibiotic co-metabolism: Kinetics, transformation products and pathways

The mutual interaction of a microalga Chlorella vulgaris with four antibiotics viz. sulfamethoxazole (SMX), trimethoprim (TMP), azithromycin (AZI), and levofloxacin (LEV) individually and in mixture was studied in batch culture. SMX, TMP, and LEV stimulated algal growth, while AZI inhibited its growth. The Combination Index (CI)-isobologram indicated antagonism of the antibiotic mixture on the growth of C. vulgaris. Higher removal efficiency was observed in the mixed antibiotic than in the single antibiotic batch cultures. Biodegradation was the main antibiotic removal mechanism with a similar antibiotic biosorption pattern in single and mix antibiotic cultures. Scanning electron microscopy and Fourier transform infrared spectrophotometry showed minor biochemical alterations on algal cells surface and a stable algal population. Monod kinetics model was successfully applied to understand the growth with respect to the removal efficiency of C. vulgaris in single and mix antibiotic batch cultures. Results indicated relatively higher specific growth rate in the mix antibiotic batch culture with removal efficiency in the order of SMX > LEV > TMP > AZI. In total, 46 metabolites with 18 novel ones of the four antibiotics were identified by using high-resolution mass spectrometry based on the suspect screening approach to propose the potential transformation pathways. Most of the transformation products demonstrated lower toxicity than their respective parents. These findings implied that C. vulgaris could be an outstanding candidate for advanced treatment of antibiotic removal in wastewater.

Acetate-assisted carbon monoxide fermentation of Clostridium sp. AWRP

Acetogens are of great interest on conversion of synthesis gas in that they can efficiently utilize CO-containing gases to produce C2 and higher metabolic products. However, high concentration of CO is known to inhibit the reduction of CO2 into formate, thereby diminishing an overall carbon fixation rate. We report that acetate supplementation can be a simple, effective approach to mitigating CO inhibition in Clostridium sp. AWRP (hereinafter called AWRP). The added acetate rapidly reduced into ethanol by the AWRP cells, which coincided with CO oxidation. From stoichiometric calculations, the acetate reduction was observed to allow carbon fixation, indicating that the CO oxidation might reduce the intracellular CO levels below inhibitory levels. Furthermore, AWRP exhibited an 83 % higher maximum specific growth rate (μmax) in the acetate-supplemented bottle cultures than in the control. In the bioreactor experiments, the AWRP culture with exogenous acetate displayed 2.9- and 2.3-fold higher titers of ethanol (232 mM) and 2,3-butanediol (23 mM), respectively, as well as μmax (2.6-fold) and maximum cell density (1.9-fold), than without acetate supplementation. These results indicate that this approach can be applied to various fermentative experiments using CO-containing gases to shorten the overall cultivation time.

Assessing the Viability of Commercial Media for the Mass Culture of Chaetoceros muelleri

The microalgae Chaetoceros muelleri is considered a highly nutritious feed for the cultured larvae of the tropical sea cucumber Holothuria scabra. Due to the cost of analytical grade culture media used in the production of C. muelleri, there is a need to evaluate cheap alternative commercial media to decrease the cost of producing quality live microalgal food. In this study, two different indoor batch culture systems (1 L glass bottles and 10 L plastic carboys) were used to evaluate the effectiveness of two conventional (modified F/2 and Walne’s) and one commercial (Epizyme AGP complete) microalgal culture media. Results of the 1 L glass bottle experiment showed that the peak cell density of C. muelleri in AGP (1,241 ± 116 x 104 cells ml-1) was not significantly different from the modified F/2 (1,584 ± 41 x 104 cells ml-1) and Walne’s medium (1,319 ± 162 x 104 cells ml-1) (Kruskal-Wallis test, p=0.78). Likewise, in the plastic carboy experiment, the maximum cell density of C. muelleri in Walne’s medium (750 ± 144 x 104 cells ml-1) and F/2 medium (653 ± 79 x 104 cells ml-1) were higher, but not significantly different from AGP (496 ± 184 x 104 cells ml-1) (Kruskal-Wallis test, p=0.43). The highest growth rate in the glass bottle cultures was the modified F/2 (0.38 div day-1), while AGP was the lowest (0.34 div. day-1). On the other hand, in carboy culture, AGP was higher (0.17 div.day-1) compared to modified F/2 (0.15 div. day-1) and Walne’s medium (0.13 div. day-1). The exponential growth phase was similar in the glass bottles, while in the carboy, the exponential phase was reached at a shorter time in the AGP treatment than those in the modified F/2 and Walne’s media. The findings showed that AGP medium is an adequate alternative to replace the conventional media (modified F/2 and Walne’s) during the secondary stock culture for C. muelleri. The viability of using cheaper and more readily available commercial AGP media for the indoor culture production of C. muelleri can contribute to cost-effective scaling-up of the hatchery production of quality H. scabra larvae and early juveniles.

Pattern of Bacterial Infections in Indian Bone Marrow Transplant Patients - Experience from Chennai India

Introduction:Bone marrow transplant, both Autograft and Allograft produces profound immune-suppression and breach of mucosal surfaces leading to many opportunistic infections. There is a difference between infection pattern in countries like India compared to western countries. The western literature is more bothered about reactivation of viral and fungal infections, whereas Indian bone marrow transplant physicians are worried about losing patient to refractory gram negative sepsis. In this study, we have tried to decode the pattern of bacterial infections in Indian transplant patients and tried to suggest an antibiotic stewardship for the same.Materials and methods:This retrospective study included all bone marrow transplants with Febrile neutropenia done at our hospital from September 2014 to July 2021. A total of 440 patients were included and their pattern of bacterial infections with culture sensitivity and response to antibiotics were noted.Results:36% of patients we included in the study were aged between 40 to 60 years and the age range was from 2 years to 72 years. 59% were autograft and among Allograft 36% were haplo-identical bone marrow transplant. Nearly half the patients presented with fever above 99.5 F and tachycardia as the presenting sign. The WBC count during first episode febrile neutropenia was less than 100cells/cumm in around 25% patients. Empirical antibiotics post culture samples were initiated within 10 min in 95% of patients. Cefoperazone Sulbactum and Amikacin were started empirically as first line in all.Culture positivity rate was 22.7% of which 60% were multi-drug resistant gram negative bacilli which were sensitive only to Colistin / Fosfomycin / Tigecycline. This 60% MDR GNB is very high which may be partially due to MDR bugs in normal intestinal flora of patients from this part of the world. The common Gram-negative bacteria are Pseudomonas, Escherichia coli and Klebsiella. This made us to change antibiotic stewardship policy to Colistin / Fosfomycin / Ceftazidime avibactum very early in course in case of second fever / Hypotension or tachycardia. Our transplant related mortality is around 3% in Allograft due to sepsis and 0% in autograft. The rate of gram positive bacteremia is only 2% and this makes us think of avoiding drugs like Teicoplanin / Glycopeptides in first line empirical therapy.Conclusion:This seven year study had shown 22.7% culture positivity rate in febrile neutropenia transplant patients of which 60% are multi-drug resistant bacteria which is highly contrary to western literature. The rate of gram positive culture growth is only 2% which is lower than western literature. This study implies the importance of region and center specific antibiotic policy for febrile neutropenia and a generalized policy may not work always.Reference:-1. Ghafur A, Devarajan V, Raj R, Easow J, Raja T. Spectrum of bacteremia in posthematopoietic stem cell transplant patients from an Indian center. Indian J Cancer 2016;53:590-12. Krüger W,et al. Early infections in patients undergoing bone marrow or blood stem cell transplantation–a 7 year single centre investigation of 409 cases. Bone Marrow Transplant. 1999 Mar;23(6):589-97. doi: 10.1038/sj.bmt.1701614. PMID: 10217190. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Lessons From a Quality Improvement Project to Standardize the Process of Gastric Biopsy Culture for Helicobacter pylori.

We conducted a quality improvement (QI) project with the aims of increasing the rate of successful primary culture. The QI project involved educational efforts among our gastroenterologists, endoscopy suite personnel, and laboratory personnel. We compared the frequency of gastric biopsy culture sent in patients with international classification of diseases 9th revision code 041.86, and 10th revision codes B96.81 evaluated by pediatric gastroenterologists at Boston Children's Hospital during the 9 months before the QI intervention (February 1, 2019 to October 31, 2019) and 9 months after the QI intervention (November 1 2019 to July 31 2020). We also compared the rate of culture growth in patients with positive histology (culture positivity), and antimicrobial susceptibilities before and after November 1, 2019. We observed an increased frequency of gastric biopsy acquisition by any gastroenterologist, obtained in 39% (28 of 71) preintervention patients compared with 67% (36 of 54) intervention patients (P = 0.004). There was an increase in the percentage of culture positivity across study periods from 21% (3 of 14) preintervention to 45% (5 of 11) postintervention (P = 0.39; 95% confidence interval, 0.64-7.00). Educational initiatives and collaborative work with staff physicians, endoscopy personnel, and hospital laboratory appear to be effective tools to increase usage of gastric biopsy culture as a diagnostic tool for H pylori infection and to increase culture positivity. Improving the surveillance of local resistance rates will improve the selection of the most effective primary treatment in specific geographic areas.

Bacterial Load Comparison of the Three Main Lineages of Mycobacterium tuberculosis Complex in West Africa

Studies have shown an association between bacterial load and virulence; however, not much is known about the diversity in this phenotypic characteristic of Mycobacterium tuberculosis complex (MTBC). This study was therefore aimed to determine the differences in bacterial load of the three most prevalent MTBC genotypes (L4, L5, and L6) in West Africa at the time of diagnosis. A total of 170 paired fresh sputum samples were collected; one part in guanidinium thiocyanate (GTC) was used for RNA extraction and tuberculosis molecular bacterial load assay (TB-MBLA), and the other part without GTC was confirmed for TB positivity using GeneXpert MTB/RIF, smear microscopy grading, and culture on Löwenstein–Jensen media slants. The 170 sputum samples comprised 155 new cases, three follow-up cases, and 12 TB negative sputum samples. The time-to-culture positivity (TTP) and degree of culture positivity (DCP) were recorded. All 122 isolates obtained were spoligotyped for lineage (L) classification, but spoligotypes were obtained from 120 isolates. Of the typed isolates, 70.0, 10.8, 10.8, 4.2, 2.5, 0.8, and 0.8% were lineages 4, 5, 6, 2, 3, 1, and Mycobacterium bovis, respectively. Further analysis of the three most prevalent lineages showed significantly shorter TTP and higher DCP by L4 compared to L5 and L6, respectively: TTP 20.8, vs. 26.5, and 28.2 days; p-value = 0.005 and DCP 1.27, vs. 0.81 and 0.29, p < 0.001. The average TB-MBLA measured bacterial load of L4 was 3.82 Log10eCFU/ml which was not significantly different from 3.81 and 3.80 Log10eCFU/ml of L5 and L6, respectively, p = 0.84. Degrees of smear microscopy L4 = 1.20, L5 = 1.20, and L6 = 0.92 and GeneXpert Cq values L4 = 17.08, L5 = 18.37, and L6 = 17.59 showed no significant difference between the lineages, p = 0.72 and p = 0.48, respectively. Retrospective analysis of a larger sample confirmed the difference in TTP, p < 0.001. In conclusion, the observed shorter TTP and high DCP of L4 could signify high growth rate in culture that is independent of total bacterial load at diagnosis.

The Effects of Stocking Density on Growth and Survival rate of Beong (Hemibagrus nemurus)

Beong are one of endogenous fish in Indonesia and still rely on catches from nature. The level of growth and survival rate in culture of beong is still low, so it is necessary to do cultivation efforts for conservation of beong, so that the beong can be cultivated intensively. One effort that can be do is biological manipulation in the form of stocking density. This study aims to determine the effect of shocking density on growth and survival rate and find out the best amount too. The study was conducted in April-May 2018 at UPT BBI Sawangan, Magelang, Central Java. The method used in this study was experiment method and Completely Randomized Design (CRD) for 4 treatments, 3 replicates with stocking dencities of A (10 fish/m2), B (30 fish/m2), C (50 fish/m2)and D (70 fish/m2). The results showed that different stocking densities gave a significant effect (Sig.&gt; 0.05) on TKP, FCR, SGR and SR. This is allegedly due to feed competition, space competition and cannibalism in Beong fish. Treatment B gave the best results at TKP, FCR, SGR and SR with a value of 1.36 ± 0.01 gr / individual, 1.15 ± 0.11, 4.58 ± 0.22% / day and 83.33 ± 3,34%.

Expanding Characterized Diversity and the Pool of Complete Genome Sequences of Methylococcus Species, the Bacteria of High Environmental and Biotechnological Relevance.

The bacterial genus Methylococcus, which comprises aerobic thermotolerant methanotrophic cocci, was described half-a-century ago. Over the years, a member of this genus, Methylococcus capsulatus Bath, has become a major model organism to study genomic and metabolic basis of obligate methanotrophy. High biotechnological potential of fast-growing Methylococcus species, mainly as a promising source of feed protein, has also been recognized. Despite this big research attention, the currently cultured Methylococcus diversity is represented by members of the two species, M. capsulatus and M. geothermalis, while finished genome sequences are available only for two strains of these methanotrophs. This study extends the pool of phenotypically characterized Methylococcus strains with good-quality genome sequences by contributing four novel isolates of these bacteria from activated sludge, landfill cover soil, and freshwater sediments. The determined genome sizes of novel isolates varied between 3.2 and 4.0Mb. As revealed by the phylogenomic analysis, strains IO1, BH, and KN2 affiliate with M. capsulatus, while strain Mc7 may potentially represent a novel species. Highest temperature optima (45–50°C) and highest growth rates in bioreactor cultures (up to 0.3h−1) were recorded for strains obtained from activated sludge. The comparative analysis of all complete genomes of Methylococcus species revealed 4,485 gene clusters. Of these, pan-genome core comprised 2,331 genes (on average 51.9% of each genome), with the accessory genome containing 846 and 1,308 genes in the shell and the cloud, respectively. Independently of the isolation source, all strains of M. capsulatus displayed surprisingly high genome synteny and a striking similarity in gene content. Strain Mc7 from a landfill cover soil differed from other isolates by the high content of mobile genetic elements in the genome and a number of genome-encoded features missing in M. capsulatus, such as sucrose biosynthesis and the ability to scavenge phosphorus and sulfur from the environment.

Independence of a Marine Unicellular Diazotroph to the Presence of NO3.

Marine nitrogen (N2) fixation was historically considered to be absent or reduced in nitrate (NO3−) rich environments. This is commonly attributed to the lower energetic cost of NO3− uptake compared to diazotrophy in oxic environments. This paradigm often contributes to making inferences about diazotroph distribution and activity in the ocean, and is also often used in biogeochemical ocean models. To assess the general validity of this paradigm beyond the traditionally used model organism Trichodesmium spp., we grew cultures of the unicellular cyanobacterium Crocosphaera watsonii WH8501 long term in medium containing replete concentrations of NO3−. NO3− uptake was measured in comparison to N2 fixation to assess the cultures’ nitrogen source preferences. We further measured culture growth rate, cell stoichiometry, and carbon fixation rate to determine if the presence of NO3− had any effect on cell metabolism. We found that uptake of NO3− by this strain of Crocosphaera was minimal in comparison to other N sources (~2–4% of total uptake). Furthermore, availability of NO3− did not statistically alter N2 fixation rate nor any aspect of cell physiology or metabolism measured (cellular growth rate, cell stoichiometry, cell size, nitrogen fixation rate, nitrogenase activity) in comparison to a NO3− free control culture. These results demonstrate the capability of a marine diazotroph to fix nitrogen and grow independently of NO3−. This lack of sensitivity of diazotrophy to NO3− suggests that assumptions often made about, and model formulations of, N2 fixation should be reconsidered.

Effect of density and mixed culture of largemouth bass (Micropterus salmoides) and pikeperch (Sander lucioperca) on growth, survival and feed conversion rate in intensive culture

In this study, two experiments were performed with the aim to optimize intensive aquaculture of largemouth bass (Micropterus salmoides). In the first 140-day experiment the effect of the initial fish density was assessed at three levels: low density (LD) 23 kg/m&lt;sup&gt;3&lt;/sup&gt;, medium density (MD) 35 kg/m&lt;sup&gt;3&lt;/sup&gt; and high density (HD) 46 kg/m&lt;sup&gt;3&lt;/sup&gt;. All three densities provided the same final Fulton’s condition coefficient (FC = 1.24–1.28), specific growth rate (SGR = 0.22–0.24%/day) and survival rate (97–100%). No cannibalism was observed at all tested densities. Feed conversion ratio (FCR = 1.39 ± 0.21 g/g) was the lowest for LD and the highest (1.61 ± 0.08 g/g) for MD. The highest fish biomass (25.7 ± 2.7 kg/m&lt;sup&gt;3&lt;/sup&gt;) was obtained at HD and this density was considered as the most effective density of all tested ones during the intensive culture of largemouth bass. The second 60-day experiment tested the effect of largemouth bass and pikeperch (Sander lucioperca) monoculture and biculture of both species on production efficiency. Higher size heterogeneity was obtained in both (mono- and bicultural) groups of pikeperch (308.91–314.56‰/day) compared to the groups of largemouth bass (279.26–284.05 ‰/day). The higher FC (1.09) was found in both types of culture in largemouth bass compared to both methods of culture in pikeperch (0.74–0.78). The lowest SGR was evident in both types of largemouth bass cultures (1.20–1.28%/day). In contrast, the highest SGR was achieved in the bicultural pikeperch (1.88%/day). Similar results like for SGR were also assessed for FCR, where the highest value of FCR was in both cultures of largemouth bass (1.44–1.48 g/g) compared to the lowest FCR in the bicultural of pikeperch (0.73 g/g). Largemouth bass in both tested types of culture had higher survival rates (99.95–99.99%) compared to pikeperch (98.61–98.63%).