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Black carrot is a prominent source of polyphenols and the cheapest source of anthocyanins in India. In this study, an attempt has been made to examine the feasibility of black carrot powder as an ingredient in bread. Black carrot bread was prepared by incorporating different concentrations of black carrot powder (BCP) at 2.5, 5.0, 7.5 and 10 %. The developed bread samples were analyzed for physical and textural quality, proximate composition, bioactive compounds, antioxidant properties, sensory characteristics, mineral content and storage quality. The results revealed that loaf volume and specific volume decreased (1995-1254 mL, 5.25-3.28 mL/g) with the incorporation of BCP into bread. Textural analysis revealed that the addition of BCP led to increased hardness in the bread (0.110-12 0.151 N), whereas the resilience (43.64-35.10 %), cohesion and springiness (89.930-13 82.146 %) decreased significantly. The content of bioactive compounds such as total phenols, anthocyanins (29.63-112.68 mg/100 g) and flavonoids increased to exceptionally high levels in BCP-incorporated bread and showed high antioxidant activity. Incorporation of BCP up to 7.5 % showed the most acceptable sensory analysis score (7.85) with a significant increase in dietary fiber (40 %) and total mineral content (50 %), which revealed that black carrot powder could be used up to 7.5 % as an ingredient into bread with high acceptability. The present study revealed significant enhancement in bioactive compounds and mineral content of bread after the incorporation of black carrot powder, which supports its immense potential in preventing hunger and oxidative stress-induced disorders in developing countries., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

To address the complex challenges faced by our planet such as rapidly changing climate patterns, food and nutritional insecurities, and the escalating world population, the development of hybrid vegetable crops is imperative. Vegetable hybrids could effectively mitigate the above-mentioned fundamental challenges in numerous countries. Utilizing genetic mechanisms to create hybrids not only reduces costs but also holds significant practical implications, particularly in streamlining hybrid seed production. These mechanisms encompass self-incompatibility (SI), male sterility, and gynoecism. The present comprehensive review is primarily focused on the elucidation of fundamental processes associated with floral characteristics, the genetic regulation of floral traits, pollen biology, and development. Specific attention is given to the mechanisms for masculinizing and feminizing cucurbits to facilitate hybrid seed production as well as the hybridization approaches used in the biofortification of vegetable crops. Furthermore, this review provides valuable insights into recent biotechnological advancements and their future utilization for developing the genetic systems of major vegetable crops.

Black carrots are rich in bio-actives but underutilized owing to their short-term availability and perishable nature. Traditionally, black carrots have been used for the preparation of Kanji-a fermented non-dairy beverage prepared using natural fermentation by lactic acid bacteria and a few spices. This plant-based probiotic beverage has high antioxidant properties but there is a risk of contamination with pathogens due to uncontrolled fermentation during storage. To enhance the availability of this nutritious beverage throughout the year and to ensure the microbiological safety of the traditional fermented product, the present study was planned to optimize the process for controlled fermentation using freeze-dried lactic acid bacterial (LAB) culture and refractance window-dried black carrot powder. The physicochemical and microbiological profiles of LAB-fermented Kanji were analysed. The dried Kanji mix can be reconstituted into naturally fermented probiotic beverage with unique flavour and aroma along with ensured microbiological safety and enhanced commercial value., (© 2023. The Author(s).)

Vegetable crops are known as protective foods due to their potential role in a balanced human diet, especially for vegetarians as they are a rich source of vitamins and minerals along with dietary fibers. Many biotic and abiotic stresses threaten the crop growth, yield and quality of these crops. These crops are annual, biennial and perennial in breeding behavior. Traditional breeding strategies pose many challenges in improving economic crop traits. As in most of the cases the large number of backcrosses and stringent selection pressure is required for the introgression of the useful traits into the germplasm, which is time and labour-intensive process. Plant scientists have improved economic traits like yield, quality, biotic stress resistance, abiotic stress tolerance, and improved nutritional quality of crops more precisely and accurately through the use of the revolutionary breeding method known as clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein-9 (Cas9). The high mutation efficiency, less off-target consequences and simplicity of this technique has made it possible to attain novel germplasm resources through gene-directed mutation. It facilitates mutagenic response even in complicated genomes which are difficult to breed using traditional approaches. The revelation of functions of important genes with the advancement of whole-genome sequencing has facilitated the CRISPR-Cas9 editing to mutate the desired target genes. This technology speeds up the creation of new germplasm resources having better agro-economical traits. This review entails a detailed description of CRISPR-Cas9 gene editing technology along with its potential applications in olericulture, challenges faced and future prospects., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Devi, Chauhan and Dhillon.)

Background: Dairy products like ice cream, yogurt and buttermilk are consumed widely due to their rich taste but these products lack anthocyanins, which are polyphenol and exhibit great antioxidant activity in both in vivo and in vitro studies. Therefore, adding a natural source of these antioxidants to the commonly consumed dairy product will be beneficial to the masses. Among all the sources, black carrots are the extraordinary and cheapest source of anthocyanins, which are commonly consumed as a natural fermented drink. In this study, an attempt has been made to examine the feasibility of black carrot concentrate as an ingredient into dairy products., Methodology: Ice cream, yogurt and buttermilk were prepared by incorporating black carrot concentrate at 2.5, 5.0, 7.5 and 10% level and were subjected to sensory analysis. The most acceptable products with 7.5% black carrot concentrate were analyzed for minerals, polyphenols and antioxidant activity. Effects of storage on physicochemical, microbial and sensory attributes of black carrot concentrate incorporated dairy products were further analyzed., Results: Sensory analysis revealed that black carrot concentrate could be used up to 7.5% as an ingredient into dairy product with high acceptability. Significant improvement in mineral content (Mg and Fe), polyphenols and antioxidant activity were reported in black carrot concentrate added dairy products. Developed dairy products exhibited an excellent amount of 24.52-113.27 mg/100g anthocyanins. Flavonoids increased by 14.52-34.62 times and Folin-Ciocalteu reducing capacity increased by 26.39-35.87 times in experimental dairy products. The storage study revealed that ice cream could be stored for more than 60 days, yogurt up to 5 days and buttermilk up to 10 days with excellent stability attributes., Conclusion: Incorporation of black carrot concentrate at the level of 7.5% resulted in high acceptability and exceptional nutraceutical property of dairy products. Incorporation of black carrot concentrate into dairy products would enhance the nutraceutical properties and mineral content of food, which could be highly significant in preventing hidden hunger and oxidative stress-induced disorders in developing countries., Competing Interests: The authors declare no conflict of interest., (© 2021 Published by Elsevier Ltd.)

Background: Single-center comparative effectiveness studies evaluating outcomes that can occur posthospitalization may become biased if outcomes diagnosed at other facilities are not ascertained. Administrative datasets that link patients' records across facilities may improve outcome ascertainment., Objective: To determine whether use of linked administrative data significantly augments thromboembolic outcome ascertainment., Research Design: Retrospective cohort study., Subjects: Patients with an acute isolated calf deep vein thrombosis (DVT) diagnosed at 1 Californian center during 2010-2013., Measures: Proximal DVT or pulmonary embolism (PE) within 180 days. We ascertained outcomes from linked California hospitalization, emergency department, and ambulatory surgery data and compared this information to outcomes previously identified from review of the center's medical records., Results: Among 384 patients with an isolated calf DVT, 333 could be linked to longitudinal administrative data records. Ten patients had a possible proximal DVT or PE (4 more clearly so) from administrative data; all were unknown from medical record review. Eleven patients with known outcomes from medical record review had no outcome from administrative data. The adjusted odds ratio of proximal DVT or PE with therapeutic anticoagulation attenuated from 0.33 [95% confidence interval (CI), 0.12-0.87] using only medical record review to 0.64 (95% CI, 0.29-1.40) using both medical record review and possible outcomes from administrative data. Restricting the outcome to diagnoses clearly involving proximal DVT or PE, the adjusted odds ratio was 0.46 (95% CI, 0.19-1.10)., Conclusions: Use of linked hospital administrative data augmented detection of outcomes but imperfect linkage, nonspecific diagnoses, and documentation/coding errors introduced uncertainty regarding the accuracy of outcome ascertainment.

Background: Screening for blunt cerebrovascular injuries (BCVIs) in asymptomatic high-risk patients has become routine. To date, the length of this asymptomatic period has not been defined. Determining the time to stroke could impact therapy including earlier initiation of antithrombotics in multiply injured patients. The purpose of this study was to determine the time to stroke in patients with a BCVI-related stroke. We hypothesized that the majority of patients suffer stroke between 24 hours and 72 hours after injury., Methods: Patients with a BCVI-related stroke from January 2007 to January 2017 from 37 trauma centers were reviewed., Results: During the 10-year study, 492 patients had a BCVI-related stroke; the majority were men (61%), with a median age of 39 years and ISS of 29. Stroke was present at admission in 182 patients (37%) and occurred during an Interventional Radiology procedure in six patients. In the remaining 304 patients, stroke was identified a median of 48 hours after admission: 53 hours in the 144 patients identified by neurologic symptoms and 42 hours in the 160 patients without a neurologic examination and an incidental stroke identified on imaging. Of those patients with neurologic symptoms, 88 (61%) had a stroke within 72 hours, whereas 56 had a stroke after 72 hours; there was a sequential decline in stroke occurrence over the first week. Of the 304 patients who had a stroke after admission, 64 patients (22%) were being treated with antithrombotics when the stroke occurred., Conclusions: The majority of patients suffer BCVI-related stroke in the first 72 hours after injury. Time to stroke can help inform clinicians about initiation of treatment in the multiply injured patient., Level of Evidence: Prognostic/Epidemiologic, level III.

Effect of post harvest treatments with calcium chloride (CaCl 2 ) and salicylic acid (SA) on physiological and biochemical parameters in relation to activities of antioxidative enzymes were investigated in radish. Radish of variety Punjab Safed Mooli 2 was harvested, washed and treated with CaCl 2 (1, 1.5 and 2%) or SA (1, 1.5 and 2 mM). Treated as well as untreated radish were placed in open trays and stored under refrigerated (5 ± 1 °C, 90% RH) conditions for 42 days. Treatment of radish with CaCl 2 and SA slowed down changes in physiological weight, colour, total soluble solids, ascorbic acid, titrable acidity, total phenolics and antioxidant activity. Treated samples exhibited higher enhancement in activities of antioxidant enzymes viz. catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), peroxidase (POD), dehydroascorbate reductase (DHAR) and monodehydro-ascorbate reductase (MDHAR) than untreated samples. However SA was found to be more effective in slowing down the metabolic activities of radish as compared to CaCl 2 treatment. Among all the treatments, 1.5 mM SA maintained the quality parameters to greater extent probably by reducing the oxidative stress to larger extent due to highest activities of antioxidative enzymes and can be used to enhance the shelf life of radish during refrigerated storage.

Importance: Deep vein thrombosis (DVT) isolated to the calf veins (distal to the popliteal vein) is frequently detected with duplex ultrasonography and may result in proximal thrombosis or pulmonary embolism (PE)., Objective: To evaluate whether therapeutic anticoagulation is associated with a decreased risk for proximal DVT or PE after diagnosis of an isolated calf DVT., Design, Setting, and Participants: All adult patients with ultrasonographic detection of an isolated calf DVT from January 1, 2010, to December 31, 2013, at the Vascular Laboratory of the University of California, Davis, Medical Center were included. Patients already receiving therapeutic anticoagulation and those with a chronic calf DVT, a contraindication to anticoagulation, prior venous thromboembolism within 180 days, or diagnosis of a PE suspected at the time of calf DVT diagnosis were excluded. Data were analyzed from August 18, 2015, to February 14, 2016., Exposures: Intention to administer therapeutic anticoagulation., Main Outcomes and Measures: Proximal DVT or PE within 180 days of the diagnosis of the isolated calf DVT., Results: From 14 056 lower-extremity venous duplex studies, we identified 697 patients with an isolated calf DVT and excluded 313 of these. The remaining 384 patients were available for analysis (222 men [57.8%]; 162 women [42.2%]; mean [SD] age, 60 [16] years). The calf DVT involved an axial vein (anterior tibial, posterior tibial, or peroneal) in 243 patients (63.2%) and a muscular branch (soleus or gastrocnemius) in 215 (56.0%). Physicians attempted to administer therapeutic anticoagulation in 243 patients (63.3%), leaving 141 control participants. Proximal DVT occurred in 7 controls (5.0%) and 4 anticoagulation recipients (1.6%); PE, in 6 controls (4.3%) and 4 anticoagulation recipients (1.6%). Therapeutic anticoagulation was associated with a decreased risk for proximal DVT or PE at 180 days (odds ratio [OR], 0.34; 95% CI, 0.14-0.83) but an increased risk for bleeding (OR, 4.35; 95% CI, 1.27-14.9), findings that persisted after adjustment for confounding factors (ORs, 0.33 [95% CI, 0.12-0.87] and 4.87 [95% CI, 1.37-17.3], respectively) and sensitivity analyses., Conclusions and Relevance: Rates of proximal DVT or PE are low after isolated calf DVT. Therapeutic anticoagulation is associated with a reduction of these outcomes but an increase in bleeding.

Background: The American Association for the Surgery of Trauma (AAST) has developed a new grading system for uniform description of anatomic severity of emergency general surgery (EGS) diseases, ranging from Grade I (mild) to Grade V (severe). The purpose of this study was to determine the relationship of AAST grades for acute colonic diverticulitis with patient outcomes. A secondary purpose was to propose an EGS quality improvement program using risk-adjusted center outcomes, similar to National Surgical Quality Improvement Program and Trauma Quality Improvement Program methodologies., Methods: This was a retrospective study of 1,105 patients (one death) from 13 centers. At each center, two reviewers (blinded to each other's assignments) assigned AAST grades. Interrater reliability was measured using κ coefficient. Relationship between AAST grade and clinical events (complications, intensive care unit use, surgical intervention, and 30-day readmission) as well as length of stay was measured using regression analyses to control for age, comorbidities, and physiologic status at the time of admission. Final model was also used to calculate observed-to-expected (O-E) ratios for adverse outcomes (death, complications, readmissions) for each center., Results: Median age was 54 years, 52% were males, 43% were minorities, and 22% required a surgical intervention. Almost two thirds had Grade I or II disease. There was a high level of agreement for grades between reviewers (κ = 0.81). Adverse events increased from 13% for Grade I, to 18% for Grade II, 28% for Grade III, 44% for Grade IV, and 50% for Grade V. Regression analysis showed that higher disease grades were independently associated with all clinical events and length of stay, after adjusting for age, comorbidities, and physiology. O-E ratios showed statistically insignificant variations in risk of death, complications, or readmissions., Conclusion: AAST grades for acute colonic diverticulitis are independently associated with clinical outcomes and resource use. EGS quality improvement program methodology that incorporates AAST grade, age, comorbidities, and physiologic status may be used for measuring quality of EGS care. High-quality EGS registries are essential for developing meaningful quality metrics., Level of Evidence: Prognostic study, level V.

Background: Although thoracic trauma is common, little is known about which factors lead to poor functional outcomes. We sought to determine which characteristics of chest wall injury predict postrecovery pulmonary symptoms or health-related quality of life., Methods: We conducted a secondary analysis of data from a randomized trial involving patients with chest wall injuries at a Level I trauma center between December 2007 and July 2012. We evaluated the overall severity of the chest wall injury-characterized primarily by the number of fractured ribs-and rib fracture location (upper, middle, and lower; anterior, lateral, and posterior) as predictors of patient-reported outcomes 60 days after injury: dyspnea burden (0-40), Modified Medical Research Council Dyspnea Scale (MMRC) (0-4), St. George's Respiratory Questionnaire (SGRQ), and normalized Medical Outcomes Study Short-Form 36 (SF-36) scores., Results: Of 189 evaluable subjects, the mean (SD) number of fractured ribs was 5 (4). The number of fractured ribs was not associated with dyspnea burden, MMRC, or SGRQ scores. After adjustment for confounders, each additional fractured rib was associated with worse SF-36 Physical Functioning and Bodily Pain scores (-0.6 units [95% confidence interval (CI), -1.1 to 0.0] and -0.8 units [95% CI, -1.3 to -0.2], respectively). Lower rib fractures were associated with worse dyspnea burden (3.4 units; 95% CI, 1.0-5.9), MMRC score (0.4 units; 95% CI, 0.0-0.8), and SF-36 Physical Functioning, Role-Physical, Role-Emotional, and Physical Component Summary scores (-4 units [95% CI, -8 to 0], -5 units [95% CI, -8 to -1], -4 units [95% CI, -8 to 0], and -4 units [95% CI, -7 to -1], respectively)., Conclusion: The overall anatomic severity of chest wall injuries does not predict worse dyspnea symptoms 60 days after injury, but it does predict increased patient perceptions of pain and physical function limitations. Lower rib fractures predict both persistent respiratory symptoms and perception of decreased overall health., Level of Evidence: Prognostic/epidemiologic study, level III.

Objective: Limited exposure and visualization and technical complexity have affected resident training in mitral valve surgery. We propose simulation-based learning to improve skill acquisition in mitral valve surgery., Methods: After reviewing instructional video recordings of mitral annuloplasty in porcine and plastic models, 11 residents (6 integrated and 5 traditional) performed porcine model mitral annuloplasty. Video-recorded performance was reviewed by attending surgeon providing audio formative feedback superimposed on video recordings; recordings were returned to residents for review. After 3-week practice with plastic model, residents repeated porcine model mitral annuloplasty. Performance assessments initially (prefeedback) and at 3 weeks (postfeedback) were based on review of video recordings on 5-point rating scale (5, good; 3, average; 1, poor) of 11 components. Ratings were averaged for composite score., Results: Time to completion improved from mean 31 ± 9 minutes to 25 ± 6 minutes after 3-week practice (P = .03). At 3 weeks, improvement in technical components was achieved by all residents, with prefeedback scores varying from 2.4 ± 0.6 for needle angles to 3.0 ± 0.5 for depth of bites and postfeedback scores of 3.1 ± 0.8 for tissue handling to 3.6 ± 0.8 for suture management and tension (P ≤ .001). Interrater reliability was greater than 0.8. In this sample, composite scores of first-year integrated and traditional residents were lower than those of senior level residents; comparatively, third-year integrated residents demonstrated good technical proficiency., Conclusions: Simulation-based learning with formative feedback results in overall improved performance of simulated mitral annuloplasty. In complex surgical procedures, simulation may provide necessary early graduated training and practice. Importantly, a "passing" grade can be established for proficiency-based advancement., (Published by Mosby, Inc.)

HK620 is a temperate lambdoid bacteriophage that adsorbs to the O-antigen of its host, Escherichia coli H. The genome of a temperature-sensitive clear-plaque mutant consists of 38,297 nucleotides in which we recognize 60 open reading frames (orfs). Eighteen of these lie in a region of the genome that we call the virion structure domain. The other 42 orfs lie in what we call the metabolic domain. Virions of HK620 resemble those of phage P22. The virion structural orfs encode three kinds of putative proteins relative to the virion proteins of P22: (1) those that are nearly (about 90 %) identical; (2) those that are weakly (about 30 %) identical; and (3) those composed of nearly and weakly identical segments. We hypothesize that these composite proteins form bridges between the virion proteins of the other two kinds. Three of the putative virion proteins that are only weakly identical to P22 proteins are 71, 60 and 79 % identical to proteins encoded by the phage APSE-1, whose virions also resemble those of P22. Because the hosts of APSE-1 and HK620 have been separated from each other by an estimated 200 My, we propose using the amino acid differences that have accumulated in these proteins to estimate a biological clock for temperate lambdoid phages. The putative transcriptional regulatory gene circuitry of HK620 seems to resemble that of phage lambda. Integration, on the other hand, resembles that of satellite phage P4 in that the attP sequence lies between the leftward promoter and int rather than downstream of int. Comparing the metabolic domains of several lambdoid phage genomes reveals seven short conserved sequences roughly defining boundaries of functional modules. We propose that these boundary sequences are foci of genetic recombination that serve to assort the modules and make the metabolic domain highly mosaic genetically., (Copyright 2001 Academic Press.)

A smooth colony strain, resistant to phages lambda and P22, was isolated from sewage and identified as Escherichia coli (strain H). Four temperate phages plaquing on strain H were isolated from sewage. The archetype, HK620, does not plaque on strains C and K12 of E. coli nor on the LT2 strain of Salmonella enterica. Bacterial mutants resistant to a clear plaque mutant of HK620 produce rough colonies. Some are also galactose-negative, a few are histidine auxotrophs, and most show sensitivity to lambda. HK620 can transduce a wide variety of auxotrophic mutants of E. coli H to prototrophy. It can recombine with lambda but its virions resemble those of P22.

DNA of lambda and seven related phages was digested with restriction endonuclease, EcoRI. Seven different fragment patterns were observed, only two of the eight phages showing identical profiles. Restriction enzyme fragment analysis is thus shown to be a sensitive tool for the differentiation of biologically indistinguishable phages.

Phage HK139 is UV inducible and lambda homoimmune and has the host range of phi80. It can recombine with lambda as well as with phi80, and in the prophage form it is found integrated between the loci his and supD.

Wild type phage HK022 was mutagenized by N-methyl-N'-nitro-N-nitrosoguanidine to induce clear plaque mutants. A total of 225 clear plaque mutants were isolated and 198 of these were assignable to one or the other of two complementation groups of the corresponding cistrons which have been designated as cI and cII, respectively. Approximately 25% of the c mutants were found to be temperature-sensitive (cts); producing turbid plaques at 32 C and clear plaques at 38 C and above. From complementation tests involving cI and cII mutants, bacteria lysogenic for cII prophage were frequently obtained. Double lysogens harboring a CI and a cII prophage were infrequently found and single lysogens harboring only a cI prophage have not been recovered. Bacterial lysogens harboring a prophage carrying a cts mutation in the cI cistron were readily obtainable. However, such lysogens show a lethal phenotype at 40 C and above, although they appear to be fully viable at 32 C. It is shown that by incubation of lysogens harboring a cts mutant of the cI cistron at 42 C, it is possible to isolate cryptic lysogens which are non-immune but harbor at least one of the phage sus+ alleles. Genetic data involving cI, cII, and two complementing sus mutants of essential genes are presented. From these data the following vegetative map is deduced: sus4--cII-cI-sus3.

Coliphage HK243 can form plaques on Escherichia coli C and K-12, but not B. The plaques are 1-2 mm in diameter and are opaque areas which clear upon exposure to chloroform vapor. During one-step growth, the eclipse and the latent periods are 20 and 30 min, respectively. Phage-infected cells continue to produce cell-free plaque-forming units for as long as 80 min after the end of the latent period, although at high multiplicities of infection (MOI) most cells lyse. No lysogenic bacteria have been found among survivors, so HK243 is considered a virulent phage. Some of the cells surviving a high MOI challenge are maltose negative and resistant to both HK243 and coliphage lambda. This fact has made possible the isolation of lambda-resistant mutants of lambda-lysogens. However, no serological cross-reaction between the phages lambda and HK243 has been detected. Genetic data involving three essential loci and a locus controlling plaque morphology suggest a circular linkage map. The virions are tadpole-shaped with an icosahedral head 68 nm long which is attached to a flexible tail 131 nm long. The phage has a linear, duplex DNA genome of molecular weight approximately 44 x 10(6) and a base composition of 33% adenine, 31% thymine, 16% guanine, and 20% cytosine.

Six non-inducible coliphages which grow on Escherichia coli C but not on K12 (C-specific) were shown to be antigenically related to P2. All six were shown to be P4 helpers and some of them could also recombine with P2.

Temperate coliphages were recovered from sewage, mammalian feces, and lysogenic strains of Escherichia coli. A total of 32 phages of independent origin were divided into six groups by applying the criteria of host range, antigenic homology, and the ultraviolet inducibility of the prophage. The demonstration of genetic interactions in some cases has confirmed the classification scheme. Nine phages were assigned to the P2 family and 19 to the lambda family. The remaining four isolates may represent some novel phylogenetic types. Phages recovered from the lysogenic strains of E. coli were all found to be P2 related, whereas a majority of the phages recovered as cell-free plaque-forming units were assignable to the lambda family. It is proposed that the biological attributes of the phages belonging to the two principal families are reflected in the distribution patterns observed. The virions of phage HK256 show multiple tail fibers and may thus represent a "new" virion form among the temperate coliphages.

Seven temperate coliphages recovered from naturally occurring lysogenic strains of Escherichia coli were found to lyse E. coli C but not K12. Four of these C-specific phages produced mutants (hrk) able to grow on K cells. The K cells harbouring HK253hrk and HK183hrk were converted so that they could adsorb and be lysed by three other non-mutant C-specific phages. HK253, HK183 and two other phages were shown to recombine with phage lambda.

Escherichia coli strains freshly isolated from natural sources are inefficient indicators of coliphages present in sewage. Four E. coli strains recently isolated from clinical specimens were mutagenized to obtain lac(-) mutants. Such mutants were infected with an F'lac(+) sex factor of E. coli K-12. Pairs of isogenic lac(-) and lac(-)/F'lac(+) strains were used as indicators of coliphages present in sewage, and it was found that such strains can be effectively used for a direct and almost selective enumeration of F-specific coliphage contents of sewage samples. Serological tests were applied to a number of F-specific phages isolated. All the isolates that were tested fell into two distinguishable antigenic classes: members of one class being related to ribonucleic acid (RNA) phage MS2 and those of the other being related to another RNA phage, namely, Qbeta. MS2-related phages have been found to be more widely distributed than the Qbeta related phages. Most habitats sampled were found to yield only one or the other kind of phage. Single-stranded deoxyribonucleic acid-containing F-specific phages were not detectable by the methods employed by us.

The attachment sites of 13 temperate coliphages were determined. Specialized transduction of proAB mutants was shown by eight isolates and of a his mutant by another two. Two isolates were concluded to integrate at atthtt and the integration site of one isolate remained undetermined.

Enterobacteria were isolated by streaking swabs of sewage and rectal swabs from human volunteers from domesticated animals. Thirty strains of human origin were identified as Escherichia coli. Out of 1,367 rectal isolates of animal origin, 21% were lysogenic (phi+), 29% were colicinogenic (col+), and 7% were col+ phi+. Out of 85 rectal samples more than 60% harbored variable numbers of col+ or phi+ bacteria. Lysogens harboring homoimmune prophages were detectable in six out of eight human subjects in sequential samples taken at weekly intervals. Chickens in Hong Kong are fed on antibiotic-containing feeds; the avian isolates contained the highest frequency (98%) of drug-resistant bacteria, whereas only 39% of the bovine and 61% of the human isolates were drug resistant. Transmissible drug resistance was demonstrable in sewage isolates and those from animal sources; the highest frequency (58%) of resistance donors was shown by the avian isolates, and the lowest (9%) was shown by the bovine isolates. Unselected marker analysis has shown that a vast majority of multiply resistant donors of diverse origins are able to transmit multiple resistance.

Temperate coliphage HK97 was isolated from pig dung. Although HK97 is antigenically unrelated to coliphage lambda, it has similar morphology, host range and immunity properties, and can recombine with it.

Temperate coliphage HK253 integrates near the proAB locus on the Escherichia coli K-12 chromosome. It can bring about specialized transduction of proAB and phoE mutants of E. coli, but it is incapable of general transduction. One of the proline-transducing particles was found to be nondefective.

Freshly voided samples of the feces of cows, pigs, and humans were analyzed for the enumeration of cell-free plaque-forming units (PFU) of coliphages and Salmonella phages. Coliphage PFU counts per gram (wet weight) of feces were found to range from less than 10(1) to greater than 10(7). Salmonella phages were found in three out of five porcine samples, but none were found in the four bovine samples analyzed. Virulent coliphages related to the phiX174/S13 serological group showed some "habitat preference" in that the S13 type of phages was found only in pig feces, whereas the phiX174 type of phages was found only in cow dung. Temperate coliphages were detectable in a majority of samples of both human and porcine origin but were infrequently found in bovine samples. About 80% of the temperate coliphages of fecal origin have been found to be serologically related to phage HK022 (Dhillon and Dhillon, 1973), and all are efficiently inducible by ultraviolet light irradiation. However, considerable diversity with the group was found when the prophage immunity pattern of 10 randomly selected isolates was examined.

Shigella and Salmonella strains isolated from clinical samples were examined. Out of 42 Shigella strains tested, 17 (40%) were found to be colicinogenic and another 3 were lysogenic. All three lysogens yielded a phage antigenically homologous to coliphage P2. Out of 30 strains tested, only 1 was found to be resistant to both neomycin and sulfamethoxazole. Out of 48 strains of Salmonella tested for drug resistance, only 2 showed multiple drug resistance. In contrast to Shigella isolates, the Salmonella isolates were infrequently (approximately 5%) bacteriocinogenic. The frequency of lysogeny in Salmonella strains was found to be 6% when tested on Salmonella typhimurium LT2, but by using a set of five indicators belonging to species Salmonella potsdam, Salmonella mbadanka, Salmonella dublin, Salmonella london, and Salmonella wandsworth, 50% of the strains were shown to be lysogenic. Salmonella phages related to P22 were recoverable from Salmonella saintpaul, Salmonella indiana, and Salmonella heidelberg. Some isolates of S. typhimurium yielded a temperature-sensitive and P22-heterologous phage which was found to be a more efficient transducer of bacterial genetic markers than P22. EcoRI-generated fragments of the DNA of some phages permitted the establishment of a clonal descent for some of the wild-type lysogenic bacterial strains. This last observation points out the potential usefulness of prophages as epidemiological markers.

Coliphage content of sewage collected from 11 different localities in Hong Kong was determined. The number of plaque-forming units (PFU) ranged from 0.036 x 10(3) to 15.9 x 10(3) per ml. In general, urban sewage tended to be richer than rural sewage both in PFU count as well as plaque morphological variation. Seventy-seven isolates were subjected to a host range study. Fifty per cent of these were able to grow on Escherichia coli K-12 as well as E. coli B. Approximately 32% were found to be male specific, and the remaining 18% were K-12 specific although sex-indifferent.