They can cause disease but are also part of the human microbiota and live on our skin, body, and on everyday objects in our environment.

它們可以致病，但也是人體微生物群的一部分，生活在我們的皮膚、身體和環境中的日常物品上。

When compared to eukaryotic cells, the structure of bacteria is less complex, due to a lack of nucleus and membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi complexes.

與真核細胞相比，細菌的結構沒有那麼複雜，因為沒有細胞核和線粒體、內質網和高爾基複合體等膜結合細胞器。

Now bacterial cells are often surrounded by several layers, which are collectively called the cell envelope.

現在，細菌細胞通常被幾層細胞膜包圍，這些細胞膜統稱為細胞包膜。

Let's start with the cell wall, which is found on the outer surface of the cell membrane and its most important role is to protect the bacteria.

先說細胞壁，它位於細胞膜的外表面，最重要的作用是保護細菌。

It consists of peptidoglycan, which usually helps differentiate whether bacteria are gram-positive or gram-negative.

它由肽聚糖組成，通常有助於區分細菌是革蘭氏陽性還是革蘭氏陰性。

Gram-positive bacteria have a single, thick layer of peptidoglycan above the plasma membrane, which allows them to retain the staining dye.

革蘭氏陽性細菌的質膜上有一層厚厚的肽聚糖，這使它們能夠保留染色劑。

And gram-negative bacteria have a thinner layer of peptidoglycan sandwiched between the surface membrane and the plasma membrane, so they can't retain the dye.

而革蘭氏陰性細菌的表膜和質膜之間夾著一層較薄的肽聚糖，是以無法保留染料。

Additionally, the cell wall helps maintain their shape.

此外，細胞壁有助於保持它們的形狀。

The round-shaped bacteria are called cocci, the rod-shaped ones are called bacilli, spiral-shaped ones are spirilla, and sometimes the same bacteria can have multiple forms, in which case they're called pleomorphic.

圓形的細菌稱為球菌，桿狀的細菌稱為桿菌，螺旋狀的細菌稱為螺旋體，有時同一種細菌會有多種形態，在這種情況下，它們被稱為多形性細菌。

Some bacteria are covered by a capsule, which acts as a shield that protects the bacteria against phagocytosis and also helps the bacteria adhere to surfaces.

有些細菌被膠囊覆蓋，膠囊就像一個保護罩，可以保護細菌不被吞噬，還能幫助細菌附著在表面上。

The capsule is considered an important virulence factor, since the strains that lack a capsule are less virulent.

膠囊被認為是一個重要的致病因素，因為缺少膠囊的菌株毒性較弱。

Underneath the bacterial cell wall, there's the plasma membrane, which is the most important layer because it encloses the cytoplasm, which is a gel-like substance composed mainly of water that also contains cell components, enzymes, and various organic molecules.

細胞質是一種凝膠狀物質，主要由水組成，其中還含有細胞成分、酶和各種有機分子。

If the plasma membrane is removed, the cell's contents spill into the environment, and the cell no longer exists.

如果質膜被移除，細胞內容物就會溢出到環境中，細胞也就不復存在了。

Now the plasma membrane is responsible for most of the cell's relationship with the and eliminating waste, and also maintains the interior of the bacteria in a constant, highly organized state.

現在，質膜負責處理細胞與外界的大部分關係，排出廢物，並使細菌內部保持恆定、高度有序的狀態。

Usually, all plasma membranes are selectively permeable barriers, which allow certain ions and molecules to pass in and out of the cell while preventing the movement of others.

通常，所有質膜都是選擇性滲透屏障，允許某些離子和分子進出細胞，同時阻止其他離子和分子的移動。

However, in bacteria, the plasma membrane has other important roles, such as respiration, photosynthesis, and the synthesis of lipids and cell wall components.

然而，在細菌中，質膜還有其他重要作用，如呼吸、光合作用以及合成脂質和細胞壁成分。

Now in the bacterial cytoplasm, there are scattered cell components such as ribosomes, which are the sites of protein synthesis.

現在，在細菌的細胞質中，散佈著核糖體等細胞成分，它們是蛋白質合成的場所。

These ribosomes can be found spread all over the cytoplasm, where they produce proteins that are destined to remain inside the cell, or they can be attached to the plasma membrane, and they are called plasma membrane-associated ribosomes, and in this case, they make proteins that will reside in the cell envelope, or get transported outside the cell.

這些核糖體可以分佈在細胞質的各個角落，它們產生的蛋白質註定要留在細胞內；也可以附著在質膜上，它們被稱為質膜相關核糖體，在這種情況下，它們產生的蛋白質將留在細胞膜上，或被運輸到細胞外。

Another structure found in the cytoplasm is the nucleoid, which is an irregularly shaped region that contains the cell's chromosome.

細胞質中的另一個結構是核仁，這是一個形狀不規則的區域，包含細胞的染色體。

The chromosomes of most bacteria are a single circle of double-stranded DNA, but some bacteria can have a linear chromosome, while others can have more than one chromosome, and these chromosomes contain the genes needed to provide instructions for protein synthesis in the cell.

大多數細菌的染色體是一圈雙鏈 DNA，但也有一些細菌的染色體是線性的，還有一些細菌的染色體可能不止一條，這些染色體包含了為細胞內蛋白質合成提供指令所需的基因。

Additionally to the genetic material contained within the nucleoid, many bacteria contain extra-chromosomal DNA molecules called plasmids.

除了核糖體中的遺傳物質外，許多細菌還含有稱為質粒的染色體外 DNA 分子。

These plasmids are small, double-stranded DNA molecules that can exist independently of the chromosome, and they can be circular or linear.

這些質粒是小型的雙鏈 DNA 分子，可以獨立於染色體而存在，它們可以是環狀的，也可以是線狀的。

Plasmids have relatively few genes, and their genetic information is not essential to the bacterium, and cells that lack them usually function normally.

質粒的基因相對較少，其遺傳信息對細菌來說並不重要，缺乏質粒的細胞通常功能正常。

However, plasmids often contain genes that confer a selective advantage to the bacterium, such as resistance to antibiotics.

不過，質粒通常含有能賦予細菌選擇性優勢的基因，如抗生素耐藥性。

Finally, the bacteria can move or attach to other cells and surfaces with the help of structures that can be found on their external surface.

最後，細菌可以藉助其外表面的結構移動或附著到其他細胞和表面。

So they have pili, which are hair-like structures that allow them to attach to other cells, and when these are shorter, they're called fimbriae and help the bacteria attach to surfaces.

是以，它們有纖毛，這是一種毛髮狀結構，能讓它們附著在其他細胞上，當這些纖毛較短時，它們被稱為緣毛，幫助細菌附著在表面上。

They can also have flagella, which are long, whip-like protrusions that allow the bacteria to move.

它們還可能有鞭毛，鞭毛是長長的鞭狀突起，能讓細菌移動。

Alright, as a quick recap, the bacteria are prokaryotic cells that play an important role in human disease and health, and can be found almost anywhere in the environment.

好吧，簡單回顧一下，細菌是原核細胞，在人類疾病和健康中發揮著重要作用，幾乎可以在環境中的任何地方找到。

Bacterial cells are often surrounded by several layers, which are collectively called the cell envelope.

細菌細胞通常由幾層細胞膜包圍，這些細胞膜統稱為細胞包膜。

They have a cell wall which protects the bacteria, determines whether they are gram-positive or gram-negative bacteria, and also helps maintain their shape.

它們有一層細胞壁，可以保護細菌，決定它們是革蘭氏陽性菌還是革蘭氏陰性菌，還有助於保持它們的形狀。

Some bacteria can also have another extra layer on top of the cell wall, called a capsule, which is a major virulence factor.

有些細菌的細胞壁上還會多出一層，稱為 "囊"，這是一個主要的致病因素。

Underneath the cell wall, there's the plasma membrane, which is the most important layer because it encloses the cytoplasm and defines the cell, having important roles such as respiration, photosynthesis, and the synthesis of lipids and cell wall constituents.

細胞壁下面是質膜，質膜是最重要的一層，因為它包圍著細胞質，定義著細胞，具有呼吸、光合作用、合成脂質和細胞壁成分等重要作用。

The cytoplasm contains ribosomes, which are the site of protein synthesis, the nucleoid, which contains the genetic material, and plasmids, which contain genes that confer a selective advantage to the bacterium.

細胞質中含有核糖體（蛋白質合成的場所）、核仁（含有遺傳物質）和質粒（含有賦予細菌選擇性優勢的基因）。