Question

Which of the following does not have nucleus in its cell?
i) Fungi
ii) Bacteria
iii) Algae
iv) Protists

Answer 1

Hint: Microorganisms or microbes can be divided into six major types: bacteria, archaea, fungi, protozoa, algae, and viruses. Unicellular eukaryotes are called protists that are not plants, animals, or fungi. Fungi is a eukaryotic organism which are heterotrophs like animals. Bacteria is a form of prokaryotic microorganism whereas algae is a form of protest.

Complete answer:
Bacteria is the microorganism which lacks nucleus in its cell. The rest of the microorganisms mentioned are eukaryotes whereas bacteria is the only prokaryote. Prokaryotes are unicellular and asexual and some prokaryotes, such as cyanobacteria, form large colonies. Prokaryotic cells do not have a membrane-bound nucleus. In fact, "pro-karyotic" is Greek for "before nucleus". They were assumed to lack cell organelles initially. With the advancement in its field of study, they were found to have prokaryotic organelles like carboxysomes, which are carbohydrate-enclosed bacterial microcompartments (BMCs). These subcellular compartments are enclosed by a shell of proteins. Membranous organelles (or intracellular membranes) have been reported in some groups of prokaryotes, such as vacuoles or membrane systems which are devoted to special metabolic properties, namely, photosynthesis or chemolithotrophy.
Bacterial growth has four phases. A population of bacteria first enters a high-nutrient environment. The first phase of growth is the lag phase, a period of slow growth when the cells are adapting to the high-nutrient environment and preparing for further faster growth. Here, proteins necessary for rapid growth are produced. The second phase of growth called logarithmic phase, also called the exponential phase, is marked by rapid exponential growth. During log phase, nutrients are metabolised at the maximum speed rate until one of the nutrients depletes. The third phase of growth is the stationary phase, caused by depleted nutrients during which the cells reduce their metabolic activity. The stationary phase is a transition from rapid growth to a stress response state. The final phase is the death phase where the bacteria run out of nutrients and ultimately die.
A bacterial cell is surrounded by a cell membrane, made primarily of phospholipids. This membrane encloses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm within the cell. Apart from protein-bound organelles in the cytoplasm which compartmentalize bacterial metabolism, bacteria have a multi-component cytoskeleton to control the localisation of proteins and nucleic acids within the cell, and to oversee the process of cell division. The genetic material of bacteria is a single circular bacterial chromosome of DNA located in an irregularly shaped body called the nucleoid, located somewhere in the cytoplasm. The nucleoid contains the chromosome with its respective proteins and RNA. Similar to all other organisms, bacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from that of eukaryotes and Archaea.

Note:
Bacteria were among the first life forms to appear and are present in most of Earth’s habitats including soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth's crust. They also live in a symbiotic and parasitic relationship with plants and animals. Bacteria grow to a particular size and then reproduce through a process called binary fission, a form of asexual reproduction. Under optimal conditions, bacteria can grow and divide as rapidly as doubling every 9.8 minutes. In cell division, two identical clone daughter cells are produced. Some bacteria, during asexual reproduction, form more complex reproductive structures so as to disperse the newly formed daughter cells. Fruiting body formation by Myxobacteria and aerial hyphae formation by Streptomyces, or budding are some of the distinct examples.

Figure: Bacteria