生物个体物质有规律地、不可逆增加， 导致个体体积扩大的生物学过程。 生长: 生物个体生长到一定阶段,通过特定方 式产生新的生命个体,即引起生命个体 数量增加的生物学过程

一、制备大量目的基因片段 二、重组DNA 三、宿主细胞 四、重组子的筛选 五、表达蛋白的收集，纯化

Using mutants to analyze the pathway or functions of genes Mutants have to be generated to analyze the pathway or functions of genes Saturation screening Overexpression Suppressor mutations Synthetic lethals Nonallelic noncomplementation

Overall Strategies Defense against complement Subversion of phagocytosis Subversion of immune responses

Types of chemotaxins – C5a attracts neutrophils and monocytes – Made by bacteria Peptide clipped off N-terminus (beginning with N￾formylmethionine) during peptide maturation after protein synthesis

Constitutive Defenses Barriers to entry – See Schaechter text, Table 6.1 Mucous membranes—covered by protective layer of mucus – Mechanical and chemical barrier that allows proper functioning

Operon fusion: transcriptional – Promoter from foreign gene – Translational sequence from reporter gene

Choosing an Animal Model Pathogen may not affect animal at all -OR￾may give different symptoms Given disease may have a number of animal models, none of which fully satisfies characteristics of disease

General aspects – Remember definition: organisms frequently found on or within body of healthy individuals – Most are bacteria, but some are viruses, fungi, and protozoa

Microbial pathogenesis—process of causing disease Colonization—presence of microbes at site of body – Does not imply tissue damage or disease symptoms – Does imply invasion of site and multiplication