Gluta with watermelon

Photos: Sorasart Wisetsin/Gluta's Facebook

Meet Gluta, a charismatic pup whose default setting is a massive doggy smile. Whether she's dressed up as a sunflower or balancing slices of bread on her head, this is one remarkable dog!

Although she's positively beaming in all her photos, you might be intrigued to learn that the outlook for this grinning canine wasn't always so bright.

Gluta and sunflowers

Gluta was rescued off the streets of Thailand three years ago by videographer Sorasart Wisetsin, but soon after this joyous adoption, her new owner learned that the dog still had several more hurdles to conquer before she could live life to the fullest.

First, Gluta was diagnosed with metritis — an inflammatory infection of her uterine wall — which required a hysterectomy. Shortly after resolving that issue, Wisetsin was heartbroken to discover that Gluta also had cervical cancer. It was a tough couple years, but after undergoing chemotherapy and a surgical laser treatment to remove a life-threatening tumor, Gluta recovered well and is now as chipper as ever.

Gluta and slices of bread

Now that Gluta is out of the woods, she spends her days posing for quirky photos and frolicking with Wisetsin's other rescue dog, Gollum (below at left), who was adopted and nursed back to health after being hit by a car.

Gluta and Gollum

Thanks to her ever-grinning demeanor and heartwarming story, Gluta is now being called the "happiest dog in the world" and has developed quite an Internet following in the last several months. Continue below for more charming portraits of Gluta, and be sure to follow her adventures on Facebook, Instagram and Tumblr.

Gluta with pond lily
Gluta in babooshka
Gluta and blue skies and flowers
Gluta and pony lily leaf
Gluta wearing a pilot cap
Gluta in a yellow bonnet
Gluta with a yellow flower
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Catie Leary is a photo editor at Mother Nature Network. Follow her on Twitter and Google+.

Catie Leary ( @catieleary ) writes about science, travel, animals and the arts.