The Mimetic pecularity of the plant world.

plant mimicry

Both, plants and animals, have in one way or the other embarked on mimetic phenomenon as a means to thrive well in this dynamic and ever challenging environmental surroundings.

The plant kingdom is overwhelmed with number of genuses and species. The plants are well-known for their adaptive stratergies to subsist in the natural territory.One such strategem is the mimicking act of the plants to sheild themselves from herbivory ,to enhance their survival rate and in some cases for pollen dissemination. For instance many species of orchids are known to imitate the bees or appear as tongue , some plants appear as stone, still others appear as bird droppings or diseased.

An early hint of this deceptive act of the plants was given by German naturalist Christian K. Sprengel in 1793. Although a less observed phenomenon, mimicry in plants is a consequence of evolution through natural selection and random mutations that are beneficial and are passed onto generations after generations, thus, confering them with survival advantage.

Some of the well-known examples of deception and trickery in plants are stated below.

bee orchidOphrys apifera:  Orchids present  the best examples of plant mimicry. One such orchid is Ophrys apifera, which resembles like a bee, hence commonly known as Bee Orchid. Native to Europe, the whole flower mimics as an insect feeding on flower. This traitorous species tricks  the male bees by appearing to them as their female counterparts, as a result, the male bees try to coupulate with the latter, furthering the dissemination of the orchid pollens.   

lithopsLithopsIf you happen to walk down the wide areas of South Africa and Namibia you chance to see interesting pebbles which are, in fact, small succulent plants Lithops , member of the plant family Aizoaceae. They protect themselves from being eaten up by looking similar to a stone. They are well adapted to sandy soil , water scarcity and soaring mercury levels.

  1. OLYMPUS DIGITAL CAMERALamiumThese herbaceous flowering plants of the family Lamiaceae are natives of Europe, Asia and North Africa.They are known to exhibit Batesian mimicry to the stinging nettles, thus, protect themselves from predators by growing in proximity to their dopplegangers. Unlike stinging nettles the dead nettles donot bear any stinging hair and are, therefore, harmless.

cryptostylisCryptostylis: Orchids are one of the enthralling plant species we have come across. These are, in fact, most deceptive species in the floral kingdom. Another one in the que is the Cryptostylis , commonly known as the tongue orchid. These mimic the female counterparts of the ichneumon wasp (commonly known as orchid dupe wasp- Lissopimpla excelsa). The male wasps are decieved by these beautiful tongue orchids, who sexually go down and try to copulate with them.

passionflower2PassifloraThe Passiflora is comprised of nearly 400 species of tendril-bearing herbaceous vine, commonly known as passion flowers. They hold a special interest among the botanists in context to their relationship with Heliconiine butterflies. These butterflies have co-evolved with these flowers. The butterflies have known to lay their eggs on the Passiflora leaves. Eggs when hatch into healthy larvae feed glutanously on the leaves, thereby, damaging them. The vine in response bear bright yellow spots that mimic the distinctive brightly coloured eggs of the butterflies. As a result, the butterflies donot lay eggs on such leaves fearing competition for their off-springs.

Unregistered RawShooter essentials 2005 1.1.3 build 15Drocera : Commonly known as the Sundews, these are the largest genera of Carnivorous plants. The leaf surface mimics tiny water droplets that appear as sundew but are , in fact, mucilaginous glands. As a result , insects often fall prey to this deception and become a supplement to fulfill their poor mineral requirements.

ophrys insectifera                 Ophrys insectiferaIt is one of the most enchanting and bewitching orchid species, commonly known as the fly orchid. These flowers perfectly imitate the female counterparts of the insects and also secrete sex pheromones. As a consequence , attract the male insects who attempt for copulation but end in pollen dissemination.

calladiumCaladium steudneriifoliumAlthough plants donot have a brain but they are smart none the less and Caladium steudneriifolium is a perfect example of this. In order to protect itself from herbivory and avoid oviposting moths they have their leaves appear as variegated and diseased. As a result, moths and caterpillars donot turn to these unhealthy plants for  any of their purpose.

Stapelia_asterias_23012_lStapelia asteriasOn crossing the South African deserts one may come across some left-over pieces of flesh, pecularity being their star-shaped; these star-shaped chunks are ,in fact, cactus-like mat forming succulent plants. These succulents have a putrid stench similar to that of rotten meat, attracting insects and flies that aid in dispersal of their pollen grains.

aviona papyracea

Aviona papyraceaAnother native of South Africa, it is dwarf perrenial herb. Its tiny green leaves are covered with white papery stipules. From a distance they appear as bird droppings while on the other hand their closer view gives them a snake-like appearances,owing to their white scaly stipules. It is their typical yet unique appearance which protects them from herbivory.

The above description surely makes us go down with enthralling characterstics of the plant kingdom. These are some of the discovered examples. There may be many more other engaging phenomenons and still new species and plants  yet to be discovered which would surely take our breaths away.

I would like to sum up my artcile with a beautiful quote by George Washington Carver:

” I love to think Nature as an unlimiting broadcasting station, through which God speaks to us every hour, if we will only tune in”.

References:

  1. Mimicry in Plants, Spencer C.H.Barrett, Scientific American, Volume 255, number 09, September 1987.
  2. Royal Botanic Gardens. http://www.kew.org
  3. http://www.plantmimicrybz2820.blogspot.in
  4. First Nature. http://www.first-nature.com
  5. The Encyclopedia of Succulents. http://www.llifle.com

The article can also be read at  http://www.indianbotanists.com/

 

Losing weight too a gender biased affair.

fatty

In general it has been observed that women , as compared to men, find it to difficult to loose weight. Well, thats because of ‘her’ differently wired brain system, as suggested by a new study conducted by the scientists at the University of Aberdeen, UK. For more details check out here.

http://www.hindustantimes.com/health-and-fitness/it-s-not-you-it-s-your-gender-why-losing-weight-is-tough-for-women/story-NHdd7ljBjw0NOa0FWHSHAM.html

The future antibiotics: Enzybiotics

enzy
source: http://www.microbiologysociety.org

Overuse and abuse of antibiotics are largely responsible for the increasing prevalence of  multi-drug resistant bacteria. Hence, the reseachers have come up with new class of antibiotics-enzybiotics, with novel mechanism of action against drug-resistant pathogens.

The global health is gripped with numerous challenges. On one side it is facing the dire consequences of the climate change while on the other side it is dreaded with plentiful of epidemics and pandemics. One such most faced challenge is increasing number of bacterial infections that have become resistant to antibiotic regimen, as a result, superbugs like MRSA and NDM-1 have dramatically escalated statistics dreading the public safety. Thus, there is an urgent need to find an alternative way to address the problem in an efficient course of action.

Enzybiotics is a hybrid of enzyme and antibiotic. These are bacterial cell wall degrading enzymes having antibacterial and/or antifungal activity, thus, proving to be a potential subsitute over conventional antibiotics. The term was first coined in 2001 by Nelson et al. They consist of lytic enzymes of class peptidoglycan hydrolases like lysins, bacteriocins, autolysins and lysozymes. The significant characertics of enzybiotics are:

  • Their novel approach for antibacterial action.
  • Their ability to kill antibiotic-resistant bacteria, and
  • Their low probability of developing bacterial resistance.

Mode of Action

Enzybiotics majorly belong to the class peptidoglycan hydrolases. When these enzymes are added exogenously to Gram positive bacteria they cause rapid disintegration of the cell wall as there is no outer membrane present to hinder their action. But, in Gram negative bacteria outer membrane obtructs their way to to the cell wall ,thus, limiting their activity. Enzybiotics have narrow host range, therefore, they selectively target their pathogenic hosts without affecting the surrounding microflora.

Major classes of Enzybiotics

  1. Bacteriocins: Bacteriocins are proteinaceous extracellular substanaces that are produced by both Gram positive and Gram negative species. They are either produced spontaneously or induced by certain chemicals such as mitomycin C. They inhibit the growth of similar or closely related bacterial strains. These are narrow spectrum class of antibiotics. Their lethal activity involves adsorption to the specific receptors on the exterior of specific bacteria, followed by metabolic, biological and morphological changes resulting in the killing of bacteria. Bacteriocins are produced by non-pathogenic bacteria that normally resides in human body. Antibiotic use results in the loss of these harmless and useful bacteria, paving way for the opportunistic pathogens to invade the human body.
  2. Lysins: Lysins, also known as endolysins or murein hydrolases are peptidoglycan degrading enzymes released by bacteriophages that help in lysis of bacterial cell wall at the end of lytic cycle to release the progeny phage particles.They are incresingly being used as antibacterial agent owning to their high efficacy and specificity. They have characterstic lysis or cell-wall binding domain and degrade peptidoglycan with glycosidase, amidase, endopeptidase, or lytic tansglycosylase activities. They are species specific but some broad spectrum lysins have also been reported. They are highly effective against Gram positive bacteria as the outer memebrane is absent as against Gram negative where outer membrane is present.
  3. Lysozymes: Also known as muramidase or N-acetylmuramide glycanhydrolase, globular protein of 129 amino acid residues.They belong to the class glycoside hydrolase that catalyse the hydrolysis of 1,4-β-linkages. They cleave the 1,4-β-linkages between N-acetyl muramic acid and N-acetyl-D-glucosamine in peptidoglycan structure. Lysozymes have been found in secretion like tears, mucus, saliva and human milk. Egg white (albumin) is an abundant source of lysozyme. It significantly contributes to innate immunity of humans . Lysozymes are most powerful natural antibacterial and antiviral subtance. It also exhibits anti-inflammatory, anti-cancer and immunomodulatory activities.
  4. Autolysins: This enzyme hydrolysis the biological component or tissue in which it is produced. These are found in all peptidoglycan containing bacteria. The enzyme functions similar to lysozyme. It cleaves the 1,4-β-linkage between N-acetyl glucosamine and N-acetyl muramic acid. They break down the peptidoglycan matrix and assist the bacterial cell in growth and cell division. They present a promising target for the development of new type of antibiotics.
  5. Defensins and cathelicidins: These are antimicrobial peptides found in the lysosomes of macrophages and polymorphonuclear leukocytes and keratinocytes. They are a part of mammalian innate immunity system that help fight bacterial infections. Cathelicidins obliterate the lipoprotein membranes of microbes enveloped in phagosomes after fusion with lysosomes in macrophages.
  6. Virion-associated peptidoglycan hydrolases (VAPGH): These are phage encoded lytic enzymes that disintegrate the peptidoglycan of the bacterial cell wall during infection. Their mode of action involves the generation of small hole through which the phage tail enters, crosses the cell envelop and releases the phage genetic material at the onset of the infection cycle. VAPGHs are highly specific, thermostable and have high modular organisation. They serve as a potential candidates for the use as enzybiotics.

Examples

Various enzybiotics with their host range, source and types are summerised below.

Enzybiotic name Enzybiotic class Source Enzymatic specificity Antibacterial range
           Ply C         Lysin Phage C1     Amidase S. pyrogens group C and E
           P al         Lysin Phage DP     Amidase S. pneumonia
Lambda SA 2-E      Endolysin Staphylococcal phage   Endopeptidase S.aureus
           P ly G         Lysin  Phage Gamma    Amidase B.anthracis
           Lyt A     Autolysin S. pneumoniae    Amidase S.pneumoniae
            Lysostaphin    Bacteriocin S. simulans Endopeptidase S.aureus, Staphylococci
Hen egg white lysozyme    Lysozyme Hen’s egg white Muraminase Gram positive bacteria

Some Potential Applications of Enzybiotics

  1. In Food industry: Enzybiotics have been widely used in food industry as food additives and preservatives like in the production of cheese and wine. The Food and Drug Administration (FDA) has given a nod to the use of enzybiotics to control Listeria monocytogenes in cheese, classifying them as GRAS (generally recognised as safe) in the year 2006 which was later extended to enzybiotic use on all food products in 2007.
  2. In Medical industry: Their novel approach for antibacterial action, ability to kill antibiotic-resistant bacteria and very low possibility to develop bacterial resistance make them potent antibacterial and antifungal agents. They are used in eye drops, toothpastes etc. Their other uses are well documented above.
  3. In Farm industry: In the recent years the misuse and overuse of antibiotics in  food producing livestock have raised a serious alarm on increasing number of antibiotic resistant bacteria, thus, escalating the risk of antibiotic resistant infections in humans. Enzybiotics present a novel way to combat the problem. They have been successfully used in treating septicaemia and meningitis in chikens and calves and also used as biocontrol agenets to control the number of Salmonellla in poultry products.

Enzybiotics present a redoubtable cover over antibiotics. Their objectionable side effects have been rarely reported. Therefore, they are very effective to be used as antibacterial and antifungal agents. Researches are being carried out on further potentials of enzybiotics and it is hoped that they present a  promosing future to medical community by help combating the antibiotic resistant strains of pathogens.

References:

  1. Ruchi Tiwari, Kuldeep Dhama,Sandip Chakraborty, Sanjay Kapoor. Enzybiotics: New weapon in the army of antimicrobials: A review. Department of Veterinary Microbiology, College of Veterinary Sciences, Uttar Pradesh. Asian Journal of Animal and Veterinary Advances 9(3): 144-163, 2014.
  2. G K Sudhakar, venkatesh Kamath B and Aravind Pai. Enzybiotics: A review. Department of Pharmaceutical Chemistry, Manipal College of Pharmaceutical Sciences, Manipal University, Manipal. International Journal of Pharmacological Research. DOI: 10.7439/ijpr.
  3. M A Daw, F R Falkiner. Bacteriocins: Nature, function and structure. Faculty of Medicine, Alfateh University of Medical Sciences, Tripoli, Libya. Micron December 27(6): 467-479.
  4.  Enzybiotics and Phages:Safe alternatives to antibiotics in the control of food safety. http://www.microbiologysociety.org

We are the SUPERORGANISMS!Part 3: The Oral Microbiome

oral microbeThe oral cavity or mouth is the major portal into the human body. The food is taken up by the mouth, masticated and mixed with saliva, making its way to the oesophagus and intestinal tract for the process called digestion. The oral cavity or the buccal cavity habours a number of bacterial species. It includes several distinct microbial habitats like teeth, gingival sulcus, tongue, cheeks, lips, hard palate, soft palate, tongue and saliva. The oral microbiome include microorganisms found within the oral cavity to the distal end of the oesophagus. But most of the studies have been obtained from within the oral cavity.

It has been estimated that around 600-700 microbial species inhabit the oral cavity. The oral microbiome majorily includes Streptococci, Neisseria, Veillonella, Actinomyces and other obligate anerobes.These species ehibit mutalistic relationship with their host, preventing other pathogens from adhering to the oral mucosa. The gingival sulcus has the highest concentration of the anerobic species, mainly Spirochaete, Vibrio and S. melaninogenicus. 

Both Gram-negative and Gram-positive bacteria colonise the buccal cavity. Some the common species found are briefed below:

Gram-positive Bacteria

  1. ActinomycesThese are facultative anaerobes that normally inhabit the mouth. They are found in the gum region. In oral cavity they are opportunistic pathogens. Their number increases in gingivitis and are found to be associated with root caries. A. israelli , an opportunistic pathogen, causes Actinomycosis which is marked by the oral abscess and leads to a condition commonly referred to as ‘lumpy jaw’. The infection can also end up in locked jaw, where mouth does not open normally. Antibiotics like  Penicillin, Tetracyclins, Erythromycins are supplemented to curb the infectious state. The best precaution to be taken is a proper oral care and practise good oral hygiene.
  2. Lactobacillus: Lactobacilli species are found in the oral cavity in the early years of a child’s life. In adults they are found in the root caries. They are highly concentrated in the saliva, on the dorsum of the tongue, in the mucuous membrane, in dental plaque and in lesser number on the tooth surface. In general, they are known to have symbiotic relationship with their host and help in preventing the adherence of other pathogenic strains in the buccal cavity. But some strains like L.acidophillus and L.paracasei are known to possess carcinogenic properties.
  3. Streptococci: These are facultative anaerobes that are the majoroty colonizers of the oral cavity. About 25 species have been known to inhabit the mouth. In general they share a commensal relationship with their host but under special circumstances they become pathogenic.  S. mutans and S. sanguinis colonise the dental surface and gingivia. Other species include S.salivarius, S. mitis, S.angiosus.  The species are associated with dental plaques and toothe decay owning to their ability to form biofilms.

Gram-Negative Bacteria

  1. Porphyromonas: P. gingivilis is an anaerobic oral microbe. It is periodontopathic pathogen that is responsible for the inflammatory response and a condition called periodontitis. It is accumulated in and around gingival crevice.The bacterium along with Trepanoma denticola and Tenerella forsythia forms the so called “red complex” , which is strongly associated periodontal destruction. Another species P.endodontalis , anaerobe , also causes peridontitis, endodontic infections , gingivitis and tooth pulp necrosis. It colonises majorly in gingival epithelial cells.
  2. Veillonella: V.parvula  is a strict anaerobe that is normally found in buccal cavity. In general, it is non-pathogenic but have been associated to cause periodontitis.Together with S.mutans it forms biofilms that are known to cause dental plaques. It is susceptible to the antibiotic penicillin.
  3. Actinobacillus actinomycetemcomitans: It is facultative anaerobe and are found in periodontal pocket of the oral cavity. It is most completely studied periodontal bacteria. It is the major cause of periodontitis, bacterial infection of the teeth that ultimately results in tooth loss. It is associates with other oral bacteria to form biofilms.
  4. Trepenoma denticola: It is a motile anaerobic bacteria found in oral cavity, concentrated in subgingival dental plaque. It is associated periodontal disease and gum inflammation. It also interacts with other oral microflora to form biofilms.

These are some of the studied bacterial populatioin found in the oral cavity and the diseases associated with them. The most given advice by the dentists to keep away the pathogenic strains is to maintain a good and healthy oral hygiene and avoiding high sugar content food supplements.