降胆固醇乳酸菌的筛选和分析比较

目的 比较7株乳酸菌各项生理特性,筛选高效、安全降解胆固醇的益生菌株,为后期开发应用奠定基础。方法 对选定菌株依次进行体外降胆固醇、胆盐水解酶（BSH）活力、人工胃肠液及胆盐耐受性、细胞粘附性能的测定和比较,并分析抗生素耐药性和抑制病原菌活性,最后利用16S rRNA基因测序确定细菌种属。结果 不同菌株各项生理指标存在差异。其中菌株ZL-2、JQI-7和PC-26的BSH酶活分别为0.010、0.015和0.030 U,可高效清除体外胆固醇,3株菌体外降解胆固醇率在58%以上;并且耐酸、耐胆盐,具备较好的HT-29细胞粘附性,不存在抗生素耐药性,可有效抑制大肠埃希菌、金黄色葡萄球菌、铜绿假单胞菌和阴沟肠杆菌生长。结论 菌株ZL-2、JQI-7和PC-26满足降胆固醇益生菌株的生物学特性,可用于进一步研究和开发。     

Equivalence of branched and unbranched Michaelian pathways concerning periodic signal transmission

Sinusoidal oscillation transmission through branched metabolic pathways is studied. Two systems are analyzed, which are composed of two convergent reaction branches and differ in the length of one of them. Linear kinetics is assumed first. Michaelis-Menten enzymes are then considered by using previous results that suggest their behavior with respect to propagation of oscillations is close to linearity around the mean input flux. As a result, there exist ways to modulate the activity of the enzymes so that propagation is equivalent for branched and specific unbranched pathways. Cells may have taken advantage of such a possibility in cases where oscillations have a biological role.     

Antibacterial sensitivity of Bifidobacterium (Lactobacillus bifidus)

The presence of the altered lysine transfer ribonucleic acid (tRNA) in Bacillus subtilis spores is strongly dependent on the medium on which the cells were sporulated. Cells sporulated on synthetic media or dilute complex media contain little or none of the new component, whereas those sporulated on concentrated complex media accumulate the altered tRNA. The accumulation begins during the fifth or sixth stage of sporulation, the formation of the tunic, and the appearance of refractility, respectively. Mutants blocked early in sporulation differ in their ability to accumulate the altered tRNA when cultured on the same complex medium. Of the four mutants examined, one failed to accumulate any of the RNA, whereas a second contained the full complement characteristic of spores. The third and fourth mutant contained small amounts of the material. It is tentatively concluded that the accumulation of the altered lysine tRNA is not obligate to sporulation but is an epiphenomenon of the process.