Genetic Changes Accompanying Increased Fitness in Evolving Populations of Escherichia Coli

Two populations of Escherichia coli, each initiated with a single clone containing a derivative of the plasmid pBR322, were maintained for long periods in glucose-limited continuous culture. In both populations, after an extensive number of generations had elapsed, clones were isolated in which the transposon Tn3 from the plasmid had integrated into the bacterial chromosome. In both cases examined, the transpositions were shown to increase relative fitness approximately 6-7%, in the environment in which the populations were maintained. The loci of integration were mapped to approximately 13.2 min (population 1) and approximately 32.8 min (population 2).     

Molecular evolution of mitochondrial 12S RNA and cytochrome b sequences in the pantherine lineage of Felidae

DNA sequence comparisons of two mitochondrial DNA genes were used to infer phylogenetic relationships among 17 Felidae species, notably 15 in the previously described pantherine lineage. The polymerase chain reaction (PCR) was used to generate sequences of 358 base pairs of the mitochondrial 12S RNA gene and 289 base pairs of the cytochrome b protein coding gene. DNA sequences were compared within and between 17 felid and five nonfelid carnivore species. Evolutionary trees were constructed using phenetic, cladistic, and maximum likelihood algorithms. The combined results suggested several phylogenetic relationships including (1) the recognition of a recently evolved monophyletic genus Panthera consisting of Panthera leo, P. pardus, P. onca, P. uncia, P. tigris, and Neofelis nebulosa; (2) the recent common ancestry of Acinonyx jubatus, the African cheetah, and Puma concolor, the American puma; and (3) two golden cat species, Profelis temmincki and Profelis aurata, are not sister species, and the latter is strongly associated with Caracal caracal. These data add to the growing database of vertebrate mtDNA sequences and, given the relatively recent divergence among the felids represented here (1-10 Myr), allow 12S and cytochrome b sequence evolution to be addressed over a time scale different from those addressed in most work on vertebrate mtDNA.      

INDIGENOUS POULTRY FEED MICROFLORA RESPONSE TO ETHYL ALCOHOL AND BUFFERED PROPIONIC ACID ADDITION

The present study was designed to compare ethyl alcohol with buffered propionic acid feed treatment on the survival of indigenous poultry feed bacteria and fungi. The aerobic bacterial poultry feed populations were not substantially reduced by either ethyl alcohol or buffered propionic acid treatments. Likewise, indigenous poultry feed fungal populations also were not markedly reduced by buffered propionic acid treatment of the feed but fungal poultry feed populations exposed to ethyl alcohol treatments were significantly lower (P<0.05) than fungal populations recovered from either control and buffered propionic acid treated feeds. Ethyl alcohol treatment may have potential for reducing fungal contamination in poultry feed.     

Monocyte-derived neutrophil chemotactic factor (MDNCF/IL-8) resides in a gene cluster along with several other members of the platelet factor 4 gene superfamily

Summary Monocyte-derived neutrophil chemotactic factor (MDNCF/IL-8, suggested gene symbol IL8) is a cytokine that chemoattracts and activates neutrophils. Using a panel of human-rodent cell hybrids that preferentially segregate human chromosomes and in situ hybridization, the MDNCF/IL-8 gene was placed on the human gene map at position 4q12-q21. This is the same location where at least three other members (platelet factor 4, melanoma growth stimulatory activity, and interferon- induced factor) of the platelet factor 4 gene superfamily reside. In addition, a restriction fragment length polymorphism was identified using MDNCF as a probe in screening genomic DNA digested with HindIII from unrelated individuals.On leave from Genetics Section, Instituto Nacional do Cancer (RJ)/ Department of Genetics, Universidade Federal do Rio de Janeiro, Brazil     

Chromosomal localization of the human interleukin 1 alpha (IL-1 alpha) gene

The human interleukin 1 alpha gene was assigned to chromosome 2 using Southern transfer analysis of human-rodent somatic cell hybrid DNAs. The gene was regionally localized to 2q12-21 using in situ hybridization to metaphase chromosomes. These results indicate that the IL-1 alpha gene maps to the same general region on the long arm of chromosome 2 as the IL-1 beta gene, which has been previously assigned.     

Metabolomic fingerprinting of bull spermatozoa for identification of fertility signature metabolites

The objective of the study was to identify the fertility‐associated metabolites in bovine spermatozoa using liquid chromatography‐mass spectrometry (LC‐MS). Six Holstein Friesian crossbred bulls (three high‐fertile and three low‐fertile bulls) were the experimental animals. Sperm proteins were isolated and protein‐normalized samples were processed for metabolite extraction and subjected to LC‐MS/MS analysis. Mass spectrometry data were processed using iMETQ software and metabolites were identified using Human Metabolome DataBase while, Metaboanalyst 4.0 tool was used for statistical and pathway analysis. A total of 3,704 metabolites belonging to various chemical classes were identified in bull spermatozoa. After sorting out exogenous metabolites, 56 metabolites were observed common to both the groups while 44 and 35 metabolites were found unique to high‐ and low‐fertile spermatozoa, respectively. Among the common metabolites, concentrations of 19 metabolites were higher in high‐fertile compared to low‐fertile spermatozoa (fold change > 1.00). Spermatozoa metabolites with variable importance in projections score of more than 1.5 included hypotaurine, d ‐cysteine, selenocystine. In addition, metabolites such as spermine and l ‐cysteine were identified exclusively in high‐fertile spermatozoa. Collectively, the present study established the metabolic profile of bovine spermatozoa and identified the metabolomic differences between spermatozoa from high‐ and low‐fertile bulls. Among the sperm metabolites, hypotaurine, selenocysteine, l ‐malic acid, d ‐cysteine, and chondroitin 4‐sulfate hold the potential to be recognized as fertility‐associated metabolites.     

微塑料对湖泊生态系统初级生产者的影响

塑料的广泛应用导致大量微塑料进入环境,尤其是水环境,从而产生环境风险。浮游植物等自养生物是湖泊系统的主要初级生产者,是湖泊食物链的关键组成部分,为食物链的上游提供能量和物质基础。同时,浮游植物也是对微塑料响应最敏感的类群。了解湖泊浮游植物等初级生产者对微塑料的响应是探究微塑料对湖泊生态系统功能影响的重要基础。总结了全球湖泊生态系统微塑料的丰度、类型、尺寸、来源等分布特征,系统分析了微塑料暴露对浮游植物等初级生产者细胞结构、基因表达和生长,以及对浮游植物叶绿素a含量、光合活性的影响,并总结了其中的影响机制。总体而言,微塑料会降低初级生产者的叶绿素a含量,剂量越高、尺寸越小,这种抑制作用越强烈;同时,微塑料也会作用于初级生产者,造成细胞膜损伤、DNA损伤,调控其相关功能基因表达,抑制其生长和光合活性等。然而,湖泊生态系统微塑料的实际检出浓度远低于室内暴露实验中的添加剂量,微塑料结构和组分也更为复杂,野外观测结果与室内培养实验之间还不能建立直接的对应关系。因此,未来的相关研究应集中在如何有效联系野外观测结果与室内培养实验结果,进一步聚焦建立可靠的、可应用推广的微塑料浓度与初级生产者之间的剂量-效应关系模型,探究微塑料对湖泊初级生产者的作用机制,为刻画微塑料对湖泊生态系统初级生产者及其功能的作用机制提供科学支撑。