Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Rare presentation of gall bladder tuberculosis in a non immuno-compromised patient

The gall bladder is least common intraabdominal organ to be involved by tuberculosis. It is either part of systemic miliary tuberculosis or abdominal tuberculosis. Isolated gall bladder tuberculosis is even rarer, can presents either as calculus or acalculus cholecystitis. Gall bladder tuberculosis presenting as a localized perforation with a sinus formation into anterior abdominal wall is unreported complication in a non immuno-compromised person. A 48-year old female presented with a gradually increasing swelling in right hypochondrium. Abdominal ultrasound showed superficial collection over right hypochondrium with intraperitoneal extension. Computed tomography showed localized gall bladder perforation with extension to the abdominal wall. Patient underwent emergency exploration and cholecystectomy with excision of sinus tract and drainage of abdominal wall abscess. Histopathological examination showed granulomatous cholecystitis suggestive of tuberculosis of gall bladder with extension into the sinus tract. She had an uneventful recovery and was treated with 6-month antitubercular therapy after surgery

Fields on fire: Alternatives to crop residue burning in India

Although intentional use of fires to transform land has decreased globally (1, 2), particularly among highly capitalized countries through regulatory and market-oriented approaches and moral suasion, regulatory strategies have been less effective in southern and eastern Asia (see table S21). Some densely populated agricultural regions in China and India buck the global trend, showing increases in agricultural fires (2). This is particularly true in northwestern India, where rice residue burning makes a substantial contribution to air pollution and short-lived climate pollutants (3, 4). Regulations are in place to reduce agricultural fires, but burning continues because of uncertainty regarding policy implementation and regarding access and returns to alternative technologies. With the field burning season soon upon us, we synthesize emerging evidence on alternatives to burning, clarify the business case for alternative practices, identify remaining uncertainties, and discuss approaches to increase their widespread adoption. Often, there are difficult trade-offs between environmental improvement and profitable economic opportunities. The case of crop residue management in northwestern India does not appear to fit this pattern and provides lessons that may be useful elsewhere. Some of the least healthy air in the world is in India (5), where polluted air is the second-highest health risk factor (6). Seasonal smog imposes enormous costs, such as major transportation disruptions and the closure of 4000 schools in Delhi in November 2017 (7). The risks peak during October and November with the burning of rice crop residues in agricultural areas (8, 9). During this period, crop residue burning contributes to major particulate pollution in Delhi and northern India (9–11). Eighty percent of agriculture in northwestern India's Indo-Gangetic plains is based on a rice-wheat cropping system (∼4.1 million ha). Concerns over groundwater withdrawals have led to a planting cycle that allows the rice crop to benefit from monsoon rains. This cycle creates a short period (∼10 to 20 days) to harvest rice, manage rice crop residue, and plant wheat. Many of the 2.5 million farmers in northwestern India prepare for wheat planting by burning an estimated 23 million metric tons of rice residue in their fields (12). India's national government recognizes both the air pollution risks and the crucial role of crop residue burning. Despite federal and state regulations since 2014 and related advisories and bans, directives against burning have been only partially enforced. The reluctance to enforce existing policies arises, in part, from the belief that profitable alternatives to burning crop residue do not exist. Any alternative to crop residue burning must be feasible, affordable, and capable of scaling to adoption by thousands of farmers. Burning could be avoided by changing the overall cropping system (e.g., growing different crops) or by adopting different rice-wheat management practices. The focus to date has been on these latter options, which we include in the scope of this study. After mechanical harvesting of rice, farmers in northwestern India have different options for sowing wheat. All options include some combination of rice residue treatments (mulching by cutting and on-field distribution, baling and removal from the field, incorporation by tilling into the field, and on-field burning), land preparation (no additional preparation, rotavate, disc and tine harrow, and plank), and seeding of wheat (using Happy Seeders, conventional seeders, other zero-till seeders, and rotaseeders). Not all combinations of these options are regularly used in northwestern India, and we focus on 10 combinations that are commonly practiced or are viewed as potentially scalable (fig. S1). The majority of farmers currently choose to burn rice straw, plow fields, and sow wheat using conventional seeders. Given variation in practices, we evaluate the public and private costs and benefits and potential scalability of 10 alternative farming options, three of which result in residue burning