Ch. 24 Man and Microorganisms [人与微生物]

1、Ch. 24 Man and Microorganisms 人與微生物Types of microorganisms 微生物的種類- bacteria 細菌 - prokaryotic cells (without nuclear membrane) 原核細胞 (沒有細胞核)- reproduce by binary fission (every 20 minutes in favourable conditions) 以二分體分裂法繁殖 (在適合的條件之下, 每20分鐘分裂一次)Now there is only one bacteria among a dish of remaining

2、food, how many bacteria is formed (1) in the 6th generation, 如果現在碟子的食物內只有一粒細菌, 有多少細菌: (1) 在第六代;(2) at this moment tomorrow, (2) 在明天的這個時間 if the rate of binary fission occurs every half hour? 倘若二分體分裂法在每半個小時發生 Ans: (1) 32 , (2) 248 , i.e. - some are pathogenic, some are useful - NOT all bacteria are h

3、armful to us. 有些是病原體, 有些是有用的 (不是所有細菌都是有害的)- viruses 病毒 - with only DNA / RNA + protein coat 只有DNA/RNA + 蛋白質- all are parasitic (they are considered living only when they are inside living cells, because they reproduce only inside the cell of its host) 所有病毒都是寄生的 (它們只在活的細胞內之時是擁有生命的, 因為病毒只在細胞內才能夠繁殖)- f

4、ungi 真菌類 - eg. Mucor, Rhizopus (classified as a separated Kingdom) 例如:白黴、黑黴(分類為一個獨立的界)Protoctists kingdom ( Protists ) 原生生物界 (原生動物)- protozoa 原生動物 - eg. Amoeba (變形蟲), Paramecium (草履蟲)- algae 藻類 - unicellular / colonial form 單細胞的/ 成團的. eg. Spirogyra (水綿) Useful micro-organisms 有用的微生物:- yeast 酵母菌 - fe

5、rmentation to produce alcohol - brewing beer / making wine 發酵, 以製造酒精: 釀啤酒/ 釀酒 - produces carbon dioxide - baking bread (to raise the dough) 製造二氧化碳: 烘烤麵包(升高生麵團)- decomposer 分解者 (saprophytic bacteria & fungi) 腐生的細菌和真菌類- important - decompose organic waste & dead body into ammonia for recycling of mate

6、rials in the ecosystem. 重要性: 分解有機廢物和死屍, 成為氨, 以利生態系統內物質的再循環- (nitrifying bacteria further change ammonia to nitrate which can be absorbed by plants.) 硝化細菌再把氨變成硝酸鹽, 它就能夠被植物吸收- symbiosis 共生 (eg. nitrogen-fixing bacteria in leguminous plant. (root nodule) 例如: 在豆類植物中的固氮細菌 (在根廇中)- produce nitrate to soil.

7、 (actually produce, not recycle) 為泥土製造硝酸鹽 (真正是製造, 而不是循環使用)- sewage disposal 污水排放 - organic sewage decomposed by bacteria (secondary treatment) 細菌分解有機污水 (次級處理) - prevent algal bloom 防止藻類過量繁殖- antibiotic production 製造抗生素 - eg. Penicillium produces penicillin. 例如: 青黴菌製造青黴素- antibiotic: chemical substan

8、ce produced by one microorganism, and has the ability to kill or suppress the growth of another microorganisms. 抗生素: 由一種微生物製造的化學物質, 它可以殺死或抑制另一種微生物的生長- it is specific in action (one antibiotic inhibits only one microorganism effectively) 它表現很專一的 (一種抗生素只對某一種微生物有效)- Clear zone in bacteria culture on ag

9、ar plate after incubation with antibiotic drops: 在培育前, 如果加入了幾滴抗生素, 細菌培養皿內會出現清澈的抑制環- The existing bacteria in the region have been killed by antibiotic. No bacteria multiplication (cell division) occurs to form milky condition. 已存在的細菌被抗生素殺死了, 沒有細菌能夠繁殖(細胞分裂)而形成乳濁的狀況- Clear solution in liquid culture o

10、f bacteria after incubation with antibiotics: 把抗生素加在細菌液體培養基內一同培養, 就會出現清澈的溶液- antibiotic kills bacteria, the dead bacterial cells sink to the bottom. No cells are present in the clear upper liquid. 抗生素殺死細菌, 而死亡的細菌會沉落底部, 沒有細胞在上部出現, 因此上面的液體變得清澈Harmful microorganisms- by parasitic & saprophytic bacteria

11、 & fungi (eg. Athletes foot) 有害的微生物: 寄生和腐生的細菌及真菌 (例如: 腳癬) - disease causing (pathogens) 引致疾病 (病原體) - decay useful materials. 使有用的物質腐爛Food Preservation 食物的保存- UHT treatment 高溫消毒 - heating with high temperature 加熱至很高的溫度- kill microorganisms by destroying the enzymes of them. 破壞微生物的酶, 從而殺死微生物oC to milk

12、 for few second - stored for months, but flavour changed) 例如: 把牛奶加熱至150 oC幾秒鐘, 可以貯藏很多個月, 但味道會被改變- pasteurization 巴斯德消毒法 - for milk and juice. 用於牛奶和果汁 - by lower temperature, with short time, then cool quickly and bottled. 用較低溫度, 較短時間, 然後立刻冷卻入樽 (75 oC for 15 seconds OR 65oC for 30 minutes) cool quick

13、ly to 10 oC. 75oC 15秒或65oC 30分鐘, 立刻冷卻至10 oC (kill most microorganisms without changing the flavour of food) 殺死大部分微生物, 而沒有改變食物的味道- must be stored in refrigerator. (for short time only.) 一定要貯藏在雪柜內 (只可以貯藏短時間) - Ultra high temperature (UHT) treatment for milk - short heating at high temperature.把牛奶以高溫消毒

14、,短暫而高溫- milk can store for long time. 這些牛奶可以貯藏很長時間- refrigeration 冷藏法, 即是放入雪柜 - at about 4oC 雪柜的溫度大約是4oC- to decrease the activities of microorganisms (NOT killing) 減低微生物的活躍度 (而不是殺死它們)- microorganisms can still grow slowly. 微生物仍然能夠慢慢地生長- food still decay after a long period of time. 經過長時間之後, 食物仍然會腐爛

15、- freezing 急凍法, 即是放入冰隔 - stop the activities of microorganisms 使微生物的活力停止- NOT killing them 不是殺死它們- they can resume activities when ice melts/thawing. 熔雪後, 微生物可以回復活力- drying (dehydration) 脫水法 (a) microorganism cannot grow due to water deficiency. (usually NOT killing the microorganisms) 微生物不能在缺乏水份時生長

16、 (通常不能殺死微生物)(b) vacuum drying: is used to make milk powder and soup powder. 真空脫水法: 用以製造奶粉及湯粉(c) freezing-drying: food frozen quickly, then water removed by low pressure. (eg. dim sum, vegetables in cup-noodles.) 急凍脫水法: 食物快速凍結, 然後用低壓脫水 (例如: 點心、杯麵中的乾蔬菜) - smoking 燻製法 - surface dry, coat with smoke whi

17、ch has chemical to inhibit bacteria growth. 使表面乾燥, 加上一層煙覆蓋著食物, 這層煙可以抑制細菌生長- eg. fish and meat/ham/bacon. 例如: 魚、肉、火腿、燻豬肉- canning & bottling 罐藏法、入樽 - it is kept vacuum to avoid bacteria entry 維持真空, 避免細菌進入 (NOT stopping the growth nor killing microorganisms) 不能使微生物停止生長, 亦不能殺死微生物(Aerobic microorganisms

18、 cannot survive/growth because no oxygen) 需氧微生物因沒有氧氣而不能不能生長- should work together with sterilization (this process kills microorganisms) 要與高溫消毒一同使用 (高溫消毒可殺死微生物)- osmotic preservation 滲透保存法 - by adding: salt / sugar / honey. 加鹽、糖、蜜糖- microorganisms killed/inactivated by removing water due to osmosis.

19、 用滲透作用的方法, 除去食物的水份, 以殺死或使微生物不活躍- eg. jam, food in syrup, ham. 例如: 果醬、浸在糖漿中的食物、火腿- pickling 醃製法 - add vinegar (salted first) - acid prevents bacteria growth. 加醋 (先加鹽): 酸可以防止細菌生長(if salt is added: also related to osmosis) 如果已加鹽: 亦與滲透作用有關- Irradiation 輻照法 - -radiation kills bacteria and moulds. 射線的輻射殺死

20、細菌和黴菌(真菌)- preservatives 防腐劑 - kill / stop the growth of bacteria. 殺死細菌或停止細菌的生長- eg. sulphur dioxide, some nitrites in ham, benzoic acid in canned food. 例如: 二氧化硫、某些在火腿中的亞硝酸鹽、在罐頭食物中的苯酸Concepts on Microorganisms1.In raising dough during making bread, the dough is kept in the oven so that yeast is kill

21、ed at high temperature. (NOT denatures).製造麵包把生麵團發起來之後, 又把生麵團放在焗爐內, 以高溫殺死酵母菌。(不接受: 變性; 有生物的東西會死, 才會變性。)2.Acidic solution (eg. vinegar), only prevents the growth of microorganisms. (Cannot kill microorganisms).酸性溶液 (例如: 醋), 只是防止微生物生長。(不是: 殺死微生物)3.Below freezing point, enzyme is inactive. (NOT denatured).Deep-freezing can:(a)prevent the growth and multiplication of micro-organisms,(b)inactivate their digestive enzymes,(c)inactivate the natural enzymes in the fo