Streptomyces caldifontis sp. nov., isolated from a hot water spring of Tatta Pani, Kotli, Pakistan

A Gram-staining positive, non-motile, rod-shaped, catalase positive and oxidase negative bacterium, designated NCCP-1331(T), was isolated from a hot water spring soil collected from Tatta Pani, Kotli, Azad Jammu and Kashmir, Pakistan. The isolate grew at a temperature range of 18-40 °C (optimum 30 °C), pH 6.0-9.0 (optimum 7.0) and with 0-6 % NaCl (optimum 2 % NaCl (w/v)). The phylogenetic analysis based on 16S rRNA gene sequence revealed that strain NCCP-1331(T) belonged to the genus Streptomyces and is closely related to Streptomyces brevispora BK160(T) with 97.9 % nucleotide similarity, followed by Streptomyces drosdowiczii NRRL B-24297(T) with 97.8 % nucleotide similarity. The DNA-DNA relatedness values of strain NCCP-1331(T) with S. brevispora KACC 21093(T) and S. drosdowiczii CBMAI 0498(T) were 42.7 and 34.7 %, respectively. LL-DAP was detected as diagnostic amino acid along with alanine, glycine, leucine and glutamic acid. The isolate contained MK-9(H8) as the predominant menaquinone. Major polar lipids detected in NCCP-1331(T) were phosphatidylethanolamine, phosphatidylinositol and unidentified phospholipids. Major fatty acids were iso-C16: 0, summed feature 8 (18:1 ω7c/18:1 ω6c), anteiso-C15:0 and C16:0. The genomic DNA G + C content was 69.8 mol %. On the basis of phylogenetic, phenotypic and chemotaxonomic analysis, it is concluded that strain NCCP-1331(T) represents a novel species of the genus Streptomyces, for which the name Streptomyces caldifontis sp. nov. is proposed. The type strain is NCCP-1331(T) (=KCTC 39537(T) = CPCC 204147(T)).

The hidden martingale restriction in Gram-Charlier option prices

A hidden martingale restriction is developed for option pricing models based on Gram-Charlier expansions of the normal density function. The restriction is hidden behind a reduction in parameter space for the Gram-Charlier expansion coefficients. The resulting restriction is invisible in the option price.

Aspects of the production of viscous capsular material by the yoghurt starter, streptococcus thermophilus

The technology of modern fermented milk production is not complicated and relies largely on the characteristics of the microorganisms used in its manufacture. Biochemical substances excreted by the starter cultures contribute to the chemical, physical and organoleptic properties of cultured milks. Chemical and organoleptic properties of yoghurt starter cultures have been widely studied over several decades. Conversely the biosynthetic processes and genetic control of the production of viscous extracellular material (slime) by selected thermophillic streptococci is still insufficiently understood. This study attempted to elucidate physiological aspects and the genetic control of slime production. An attempt to chemically induce ropiness was also preformed. Twenty strains of Gram positive, thermo-tolerant, milk dotting, catalase negative cocci were collected from a variety of sources. All strains were identified as Streptococcus thermophilus. Four of the isolates were identified as capable of producing an extracellular, ‘ropy’ capsular material. A negative staining method for highlighting capsular material under light microscopy was described. Ropy isolates displayed thick capsular zones of between 6-8 μm. The isolates graded as non-ropy produced only small capsular zones (less than 2 μm); two variants displayed no capsular material. Instability of the ropy phenotype during subculture and prolonged storage was described for all four ropy isolates at varied temperatures. Instability during transfer was reported as moderate with a loss of no more than 45% of ropy colonies after 15 subcultures at 48°C A significant increase in instability, during transfer, associated with an increase in incubation temperature (37-48°C) was also reported. Prolonged storage of ropy variants over ten days resulted in a drop in the number of ropy colonies. The loss was minimal when cultures were stored at 8°C, but excessive (approaching 100%) at 37°C This suggested the presence of capsular degradative substances. Analysis of the plasmid profiles of 20 strains identified only two strains harboured plasmid DNA. All plasmids were small, less than 23kilobases, and each strain possessed a single plasmid species. Only one ropy strain contained plasmid DNA that was shown, with the aid of curing experiments, not to be linked to production of the ropy phenotype. The amino acid analogue p-fluoro-DL-phenylalanine was unsuccessful in generating ropy colonies from non-ropy variants of Streptococcus thermophilus at low concentrations. Some technological considerations for the use of ropy variants of Streptococcus thermophilus in yoghurt starter cultures were made.

Silver sulfide as a staining agent for scanning electron microscopy of nylon 6/MXD6 blends

BACKGROUND: In transmission and scanning electron microscopy imaging, the ability to obtain sufficient contrast between the components of a blend when they are both of a similar chemical structure still remains problematic. This paper investigates the domain morphology of a polymer blend containing two polyamides, nylon 6 and the semi-aromatic polyamide poly(m-xylene adipamide) (MXD6), using scanning electron microscopy in backscattered electron imaging mode. The efficiency of three staining agents, ruthenium tetroxide, phosphotungstic acid and silver sulfide, in obtaining optimum phase contrast between the two polymers is discussed.
RESULTS: The use of silver sulfide as a staining agent was found to be a fast and reliable approach which required basic sample preparation and provided excellent compositional contrast between the phases present in the nylon 6/MXD6 blends compared to the other staining agents.
CONCLUSIONS: The technique described in this paper is believed to be a novel and versatile method that has the potential to further improve the ability to study complex polymer blends where one polymer contains an aromatic ring.

Corneal staining and cell shedding during the development of solution-induced corneal staining

Purpose. This non-dispensing cross-over study was conducted to determine if lenses presoaked in Opti-Free RepleniSH (OFR) or ReNu MultiPlus (RMP) cause solution-induced corneal staining (SICS) and subsequent cell sloughing before the typical 2 h in vivo examination point.

Methods. Study lenses (PureVision) were worn bilaterally by 13 participants for periods of 15, 30, 60, and 120 min using two different contralateral care regimen pairings. The lens worn on the test eye was soaked overnight in either OFR or RMP and the control eye in Clear Care (CC). After lens removal, corneal staining was rated on a scale of 0 (negligible) to 100 (severe) for four peripheral quadrants and the central region, and the differential global staining score was calculated by subtracting baseline staining scores. Following the staining assessment, corneal cells were collected from the ocular surface using a non-contact irrigation system to determine ocular cell shedding rates.

Results. Differential global staining score with OFR was greater than CC with the differences being statistically significant at 30 and 60 min (p < 0.01). Maximum staining with RMP was significantly greater than OFR and peaked after 60 and 120 min of lens wear (p < 0.01). On average, 710 ± 470 ocular cells were collected after lens wear, with similar shedding seen independent of solution or lens wear duration (p > 0.05).

Conclusions. SICS occurred earlier but to a significantly lower degree when PureVision lenses were presoaked in OFR compared with RMP, while lenses presoaked in CC did not cause SICS. Ocular surface cell shedding after lens removal was not impacted by lens wear durations of <=2 h.

Corneal staining as a response to contact lens wear

Objective: To review the effects of contact lenses on the corneal surface.

Methods: A review of the literature and in-house research of corneal staining and its various forms of presentation.

Results: Corneal staining manifests in many different forms. The severity of staining or insult of the cornea is usually determined by the extent (area of coverage), density, and depth. The cause of staining is multifactorial, and its location is often linked to the type of lens that is being worn, the solution used to clean/disinfect the lens, the state of hydration of the soft lens, and the state of the cornea that has been affected by the lens.

Conclusions: Sodium fluorescein dye effectively highlights corneal integrity changes referred to as corneal staining. This review describes the manifestations, the cause, the mechanisms, and the methods of remediation of corneal staining.

Impact of a rub and rinse on solution-induced corneal staining

Purpose. To investigate whether the inclusion of a rub and rinse step before contact lens disinfection has an impact on solution-induced corneal staining.

Methods. This was a prospective, double-masked, single investigator study. Twenty participants were recruited for two visits, where balafilcon-A lenses were worn bilaterally for 2 h. Each pair of lenses was prepared using two different methodologies. The “control” lens was transferred from the blister pack directly into a storage case containing polyhexamethylene biguanide-based lens care solution. The contralateral “test” lens was rubbed and simultaneously rinsed using the same polyhexamethylene biguanide-based care solution, for either 60 s (visit 1) or 20 s (visit 2). Both lenses were then soaked in the solution overnight. After baseline corneal staining assessments, the lenses were inserted following a randomized contralateral model. After 2 h, lenses were removed, corneal staining was regraded, and comfort scores were obtained.

Results. Rubbed and rinsed test lenses induced significantly less corneal staining than control lenses for all participants during visit 1 (mean ± SD: 516 ± 843 vs. 2170 ± 902; p < 0.001) and visit 2 (522 ± 417 vs. 2091 ± 965; p < 0.001). There was no significant difference between the test lenses during visits 1 and 2 (p = 0.72) or controls (p = 0.50). Comfort scores did not differ between eyes (p > 0.05).

Conclusions. Corneal staining induced after 2 h of lens wear with the combination of balafilcon-A and polyhexamethylene biguanide-based lens care solution can be significantly reduced by including a rub and rinse step before overnight soaking. Further work is required to establish the longevity of this effect during the monthly wearing cycle.

Gram-scale and template-free synthesis of ultralong tin disulfide nanobelts and their lithium ion storage performances

Ultralong SnS2 nanobelts with a high production yield up to _98% were synthesized via a gram-scale and template-free solvothermal route. The synthetic mechanism of these intriguing ultralong nanobelts was proposed to be from the synergetic effect of the layered CdI2-type structure of SnS2 and surfacemodification of the capping reagent dodecanethiol. The resulting SnS2 nanobelts showed a high specific capacity of 640 mA h g_1 and stable cycling ability (560 mA h g_1 after 50 cycles), which is much better than a graphite anode.