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Aiming at developing cyanobacterial-based biosensors for heavy metal detection, expression of heavy metal inducible genes of the cyanobacterium Synechocystis PCC 6803 was investigated by quantitative RT-PCR upon 15 minutes exposure to biologically relevant concentrations of Co 2+ , Zn 2+ , Ni 2+ , Cd 2+ , Cr 6+ , As 3+ and As 5+ . The ziaA gene, which encodes a Zn 2+ -transporting P-type ATPase showed a markedly increased mRNA level after incubation with Cd 2+ and arsenic ions, besides the expected induction by Zn 2+ ions. The Co 2+ efflux system-encoding gene coaT was strongly induced by Co 2+ and Zn 2+ ions, moderately induced by As 3+ ions, and induced at a relatively low level by Cd 2+ and As 5+ ions. Expression of nrsB , which encodes a part of a putative Ni 2+ efflux system was highly induced by Ni 2+ salts and at a low extent by Co 2+ and Zn 2+ salts. The arsB gene, which encodes a putative arsenite-specific efflux pump was highly induced by As 3+ and As 5+ ions, while other metal salts provoked insignificant transcript level increase. The transcript of chrA , in spite of the high sequence similarity of its protein product with several bacterial chromate transporters, shows no induction upon Cr 6+ salt exposure. We conclude that due to the largely unspecific heavy metal response of the studied genes only nrsB and arsB are potential candidates for biosensing applications for detection of Ni 2+ and arsenic pollutants, respectively.

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Authors: Gy. Károlyi, T. Keleti, G. Kós and I. Ruzsa

Abstract  

We study those functions that can be written as a finite sum of periodic integer valued functions. On ℤ we give three different characterizations of these functions. For this we prove that the existence of a real valued periodic decomposition of a ℤ → ℤ function implies the existence of an integer valued periodic decomposition with the same periods. This result depends on the representation of the greatest common divisor of certain polynomials with integer coefficients as a linear combination of the given polynomials where the coefficients also belong to ℤ[x]. We give an example of an ℤ → {0, 1} function that has a bounded real valued periodic decomposition but does not have a bounded integer valued periodic decomposition with the same periods. It follows that the class of bounded ℤ → ℤ functions has the decomposition property as opposed to the class of bounded ℝ → ℤ functions. If the periods are pairwise commensurable or not prescribed, then we get more general results.

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Authors: R. Božac, I. Kos, Z. Janječić, Ž. Kuzmanović, M. Konjačić and J. Nežak

An investigation has been carried out on the effect of different crossbreeds on chemical and sensory profiling of Croatian representative pork products, Istrian hams. Due to the original trimming of hams (without skin and subcutaneous adipose tissue) the total weight loss was significantly higher (41.67–43.69%) in all three genotypes (Swedish Landrace×Dutch Large Whit ×Pietrain (SL×DLW×P), Dutch Large White×Swedish Landrace (DLW×SL) and Dutch Large White×Duroc (DLW×D)) in comparison with the Italian and Spanish hams with skin and subcutaneous adipose tissue. Hams from DLW×D genotype had a significantly lower (P<0.01) total weight loss (41.67%) and, in comparison with the Spanish and Italian hams, Istrian ham contains much less moisture (45.05–46.35%). The content of total saturated, monounsaturated, polyunsaturated fatty acids and cholesterol was similar in all crossbreeds (P>0.05). The cholesterol level is low (541.9–555.9 mg kg−1), which makes Istrian dry-cured ham a dietary product. Hams from DLW×D had significantly more visible intramuscular fat (P<0.01) than hams from SL×DLW×P crossbreeds. The colour of muscle tissue, seasoned flavour, taste, saltiness, total mouth consistency (tender, melting, stringy) and tactile consistency were best in genotype DLW×D.

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Pherocon AM (PhAM) trapping and visual counting are two commonly used methods for identifying maize fields in the USA that contain a sufficient number of adult western corn rootworms (WCR), Diabrotica virgifera virgifera LeConte to cause economic root damage by larvae the following year. Therefore, the estimation of adult WCR population plays an important role in management decisions (rotation or treatment). The goals of this study were (1) to compare adult WCR data obtained by PhAM trapping to “whole plant count” data in different maize developmental stages, (2) to determine the period in which the data obtained by both methods show the highest correlation, (3) to determine the regression curve between capture of WCR on PhAM as an independent variable and number of WCR observed by visual plant count, and (4) to determine if the “whole plant count” method can serve as a substitution for PhAM trapping under European conditions. Three samplings were conducted in 2006 in 38 fields in Croatia and one sampling was conducted in 22 fields in Serbia. Sampling in Croatia was conducted when maize plants were in the R 65-69, R 73-77 and R 79-85 developmental stages according to BBCH identification keys of maize. Sampling in Serbia was conducted when maize plants reached R 69-71 developmental stages. Three to six PhAM traps were placed in each 0.5 to 4 ha maize field seven days prior to sampling. Visual counts were conducted on the same day as trap inspections. Adult WCR densities in the PhAM traps were correlated to adult densities on whole plants. Statistical analyses comparing the results of PhAM trapping with the visual “whole plant count” method showed that there is a significant medium to strong correlation between them. Correlation coefficients varied depending on the data used in the analysis. When sampling was conducted in the first half of August (maize developmental stages R 69-77), the correlation coefficients were the highest (r(R 6971) = 0.8677 and r(R 73-77) = 0.706). Coefficients of determination were the highest as well [r2 (R 69-71) = 0.753; r2 (R 73-77) = 0.4984]. Therefore, the most appropriate period for sampling is during the first half of August. At that time, the majority of the maize plants were between the R 69 and R 77 developmental stages. According to the results, 0.5–1 visually determined adult/plant corresponds to 40 adults/trap/week. This shows that both methods are equally useful for estimating the population densities of WCR in the Central European region.

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