Topic 1: Intro to Prokaryotes. Not Eukaryotes !

SEPTEMBER 21,2015

Hi everybody!

This is my first entry for my 3^rd semester. I hope that I can improve my study, at the same time polish my writing skills. Before we go through the lecture notes, we were asked to do summarization in Padlet on this subject which is physiology. You can click on Padlet to check it out ;)

Okay, the first topic is Introduction to Prokaryotes. I feel that this topic often repeated. If I am not mistaken, since 1st semester, I already learned about this topic. Therefore, I should master about PROKARYOTES and explore more since this is my 2^nd or more times learn about it.

 

As we all know, prokaryotes are divided into 2 domains which are BACTERIA (large domain) and ARCHEAE. This is the basic thing in microbiology which I had been enlightened on some of microorganism’s diversity.

First and foremost, why does prokaryotes named as ‘PROkaryotes’? This is because, it is ¹lack of nucleus and ²no membrane bound organelles. Most of prokaryotes consist a single cell, UNICELLULAR but a few multicellular (e.g. myxobacteria) ß why?

Info :

Myxobacteria are Gram-negative bacteria which secreting lipopolysaccharides as outermembrane and include wide variety of pathogen as it is facultative anaerobes. It is predominantly live in the soil and feed on insoluble organic substances (heterotroph).

From the picture shown above, the phylum is PROTEOBACTERIA. It was the largest division of bacteria. That is why, it is exist as multicellular of prokaryotes. The 'fruiting bodies' allows accumulation of the extracellular enzymes that are used to digest food, at the same time increase feeding efficiency. This type of prokaryotes does involved in nitrogen fixation (how?) and it is elongated rods that glide across solid surfaces. Myxobacteria are defined based on the rRNA (16s).

 

Other example is Thiomangarita namibiensis. It is a gram-negative coccoid Proteobacterium, found in the ocean sediments of the continental shelf of Namibia. It is one of the largest bacteria ever discovered and collecting nitrate and oxygen in water above the bottom in case of being resuspended and collecting sulfide in the sediments. It is also very easy to notice because it shines like a pearl. The pearl color gives it the name “Sulfur Pearl of Namibia”. The vacuole takes up about 98% of the interior. There are a few sulfur globules and the cytoplasm that fill the remainder of the space. It needs the large vacuole in order to store the nitrate it needs for survival because it can not move. Since they can not move they wait for what nitrate they are given. Each time there is a storm the ocean floor is stirred up and the mucous sheath that links the cells together catch the nitrate. The amount of nitrate that they capture allows them to go for about three months before they will die of starvation. They type of environment that they are in allows them to obtain the sulfur they need to break down the nitrate which keeps them alive.

 

Thiomangarita namibiensis

 

The Gram-positive bacteria has cytoplasmic lipid membrane and thick peptidoglycan layer.

Teichoic acids + lipoids àlipoteichoic acids, which serve as chelating agents (chemical compounds (usually organic compounds) that form complexes with metal ions or other substrates), and also for certain types of adherence. For information, peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme DD-transpeptidase. Some can produce endospore, when the environment becomes more favorable, the endospore can reactivate itself to the vegetative state. Most types of bacteria cannot change to the endospore form. Examples of bacteria that can form endospores include Bacillus and Clostridium.
 

Bacillus anthracis

Clostridium perfringens

Next, for Streptomyces, it has ability to produce bioactive secondary metabolites (such as antifungals, antivirals, antitumorals, anti-hypertensives, immunosuppressants, and especially antibiotics). In the techniques of their production, infectious diseases still remain the second leading cause of death worldwide, and bacterial infections cause approximately 17 million deaths annually, affecting mainly children and the elderly. Self-medication and overuse of antibiotics is another important factor that contributes to resistance, reducing the lifetime of the antibiotic, thus causing the constant need for research and development of new antibiotics.

Source: 

The Brazilian Journal of Infectious Diseases, Volume 16, Issue 5, September–October 2012, Pages 466–471

 

Lactic acid bacteria (LAB) are extensively utilized in various food fermentations. The capacity of LAB to produce and secrete protein has been initiated to improve their use as production hosts for applications in food, feed and health care industries. Furthermore, LAB are already used in several industrial processes that could benefit from increased production of homologous or heterologous proteins. The majority of the expression and secretion studies have been performed with Lactococcus lactis, which is the most extensively investigated lactic acid bacterium. The basic knowledge of protein expression and secretion in LAB is still, however, very limited when compared to that of Escherichia coli and Bacillus subtilis. Furthermore, although recent studies have demonstrated the capacity of LAB to express and secrete foreign proteins, the evaluation of the limits of LAB in protein production requires further development of genetic tools, like new expression and secretion vectors and more knowledge about gene regulation and secretion machinery.
Source: 

Wikipedia

 


Other prokaryotic diversity is cyanobacteria which obtain their energy from photosynthesis. It is most successful group of microorganisms on earth. They are the most genetically diverse; they occupy a broad range of habitats across all latitudes, widespread in freshwater, marine, and terrestrial ecosystems, and they are found in the most extreme niches such as hot springs, salt works, and hypersaline bays. Photoautotrophic, oxygen-producing cyanobacteria created the conditions in the planet's early atmosphere that directed the evolution of aerobic metabolism and eukaryotic photosynthesis. Cyanobacteria fulfill vital ecological functions in the world's oceans, being important contributors to global carbon and nitrogen budgets.

blue-green algae

An evolutionary lineage is a sequence of species, that form a line of descent, each new species the direct result of speciation from an immediate ancestral species. Lineages are subsets of the evolutionary tree of life. Lineages are often determined by the techniques of molecular systematics.


Treponema pallidum

                                                 

Spirochaetes is a double-membrane bacteria, most of which have long, helically coiled (corkscrew-shaped) cells. Spirochaetes are chemoheterotrophic in nature. It is distinguished from other bacterial phyla by the location of their flagella, sometimes called axial filaments, which run lengthwise between the bacterial inner membrane and outer membrane in periplasmic space. These cause a twisting motion which allows the spirochaete to move about. When reproducing, a spirochaete will undergo asexual transverse binary fission. Most spirochaetes are free-living and anaerobic, but there are numerous exceptions. It is caused Lyme disease which is fastest growing vector-borne disease and live in the colon. Treponema pallidum is an obligate internal parasite which causes syphilis, a chronic human disease.

Green sulfur bacteria obligate anaerobic photoautotrophic bacteria. Green sulfur bacteria are nonmotile (except Chloroherpeton thalassium, which may glide) and occur in spheres, rods, and spirals. The green non slfur bacteria contain genera Chloroflexus.

Green Non-sulfur bacteria

Green Sulfur Bacteria

I am interested in Deinococcus radiodurans known as ‘Conan the Bacterium’. Before that, what is meant by radiurans? It is actually mean radiation surviving. It can survive cold, dehydration, vacuum, and acid, and is therefore known as a polyextremophile and has been listed as the world's toughest bacterium in The Guinness Book Of World Records.

Deinococcus radiodurans

The discovery of methanogens helped produce the idea for the kingdom Archaeobacteria, that would include methanogens (can grow on CO2 and H2 as their sole energy source), some extreme halophiles (large amounts of salt), and some extreme thermophilic sulfur-dependant organisms. Archaea only been detected by analysis of their nucleic acids in samples from their environment. Archaea were initially viewed as extremophiles living in harsh environments, such as hot springs and salt lakes, but they have since been found in a broad range of habitats, including soils, oceans, marshlands and the human colon, oral cavity, and skin. Thermoplasma are able to change its shape due to condition surround it. There would have larger in surface area. The smaller the size, the larger the suface area

Archaea

Pyrolobus fumarii



Thermoplasma pallidum

 

 

Extreme acidic environments are characterized by their high metal content and lack of nutrients (oligotrophy). Macroscopic biofilms and filaments usually grow on the water-air interface or under the stream attached to solid substrates (streamers). In the Río Tinto (Spain), brown filaments develop under the water stream where the Gram-negative iron-oxidizing bacteria Leptospirillum spp. (L. ferrooxidans and L. ferriphilum) and Acidithiobacillus ferrooxidans are abundant. These microorganisms play a critical role in bioleaching processes for industrial (biominery) and environmental applications (acid mine drainage, bioremediation). The aim of this study was to investigate the physiological differences between the free living (planktonic) and the sessile (biofilm associated) lifestyles of Leptospirillum spp. as part of its natural extremely acidophilic community.

I think, that is all for this entry on the first topic of Physiology... Thank you :)